Locking Diffs vs Torsen

[knightjp]

Every one knows that if you are going off roading, having locking diffs is a good option. I guess that is why they are a standard fit on the Power Wagons. I was thinking about fitting lockers to my Ram, but this came across this video talking about differentials..


The military Humvees use Torsen differentials. Reading up on them, it seems like a really much better LSD and possibly a good fit for a vehicle that is a daily driver and does some weekend off-roading. Even Ford saw it a good fit to add a torsen front diff in their Raptor; while Ram's TRX is still just an open front diff.

So, would Torsen diffs, front and back a good fit for my needs or should I just consider using E-lockers or cable lockers.

 

[HEMIMANN]

Every one knows that if you are going off roading, having locking diffs is a good option. I guess that is why they are a standard fit on the Power Wagons. I was thinking about fitting lockers to my Ram, but this came across this video talking about differentials..


The military Humvees use Torsen differentials. Reading up on them, it seems like a really much better LSD and possibly a good fit for a vehicle that is a daily driver and does some weekend off-roading. Even Ford saw it a good fit to add a torsen front diff in their Raptor; while Ram's TRX is still just an open front diff.

So, would Torsen diffs, front and back a good fit for my needs or should I just consider using E-lockers or cable lockers.

They are better. Torsen is just a mechanical system for locking without electronics, is all. They are expensive. I have it. American Axle Manufacturing (AAM) calls their version Trac-Rite.

Torsen and e-locker perform the exact same function - they just actuate in different ways. Your choice. I'd go with whichever you can find is less costly.

I was not happy to read here FCA is ditching Torsen back to wet clutch limited slip axles. I got a Ram for it being a Ram - not a Ford or a GM.

 

[kurek]

For almost everything faster than a crawl a geared (Torsen or similar) LSD is going to be better than a locking diff or a clutch LSD because it is always engaged to its full capacity - in other words there is no transition from disengaged to engaged, or from partially loaded to fully loaded, or from slip to response as you'll find with a locking diff, a clutch LSD or traction control (respectively).

For the following talk I'm going to assume no special tricks by the driver, no traction control, and 2 wheel drive - this is to keep it simple and focused on the differential's direct action alone.

A helical LSD is never trying to behave as a full lock and so as long as your driven wheels have more traction on the ground than the gears have friction on each other inside the carrier it will always allow both driven wheels to receive torque at differing speeds. That means it is equally effective while going around corners and this is why you'll occasionally see performance road cars with this kind of diff - at least historically. (Note that it will still effectively "lock" when you're on an extremely low traction surface and apply too much throttle)

The down side does come in when you are crawling on very uneven terrain and lift a tire, or when you need an awful lot of torque on a slippery surface like drawing a boat up a slick ramp or pulling a trailer on a wet dirt road (or retrieving a parked trailer on a dirt lot... you get the idea) . The left and right driven wheels on a geared LSD need to have around the same traction as each other.. like within a range of ratios. This ratio range varies by LSD manufacturer and varies to a lesser extent with lubricant type but generally it's somewhere between 3:1 and 6:1. If the difference in traction between the left and right is greater than that ratio it's just going to act like an open differential.

To put that in real terms if you are on a slick road and your left wheel has enough traction to give you 200 lb of thrust and your right wheel has enough traction to give you 100 lb of thrust, the most total thrust you can get with an ordinary open differential is 200 lbs, 100 from each wheel. If you had a helical LSD the ratio between the left and right is 2:1, that's within its range of ratios so in the same situation you could get 300 lb of thrust (200 from the left wheel and 100 from the right wheel). If you're stuck enough to need more than 300 lb of thrust it would just spin both wheels.

Now change the situation, if you were in a "V" shaped ditch at an angle with two diagonal wheels in the air you might have enough traction with one tire for 1000+ lb of thrust but the opposite wheel is dangling in the air. On both an open differential and a helical differential you're going nowhere because any number is an infinite ratio from zero. Even if you only need 50 lbs of thrust to get moving, 50:0 is a much bigger ratio than 6:1, the helical diff is just going to act like an open diff. Meanwhile a clutch LSD with preload will supply that 50 lbs to both sides because for any amount of torque less than the preload it's basically a spool. And of course if you had an automatic or selectable full locker well obviously that's able to direct full torque to a single wheel when engaged.

To summarize on a helical LSD:

Pro: Seamless, proactive torque distribution while moving including when applying power around a corner - this makes it a very smooth and addictive driving experience 99% of the time.
Con: Becomes either an open differential or a spool under the most extreme conditions (specifically when either of those is NOT the thing you want) such as glare ice or rock crawling

Another aspect of any active or torque-distributing differential is how it plays with traction control and vehicle stability control. First with traction control, as it turns out they all play very nicely with that and in fact traction control amplifies the best attributes of both clutch and helical LSD's and it does this without having to be told it's there.

Vehicle stability control is a different animal. If you had a large safe playground covered in loose gravel, accelerate above ~25mph or so and begin sawing your steering wheel left and right (this is hypothetical, I am not advising anyone to actually do this, usual internet disclaimers don't be an idiot) any modern vehicle with stability control will begin individually braking your wheels while reducing throttle to prevent a spin-out or roll-over. This could become a problem if you install a LSD because now braking input from either side would be necessarily transferred across the axle. If the manufacturer is expecting this (as in Raptor) they would naturally encode the behavior to account for that but it would be impossible for an outsider to predict how this would differ on a vehicle not originally designed to have that kind of differential. My instinct would tell me "not much" and in particular not much on a rear axle but in collisions lives are lost or saved by mere inches so it's all worth taking the time to think about.

One last note on this is the front axle. The way that the front axle is built on 1500's it is manufactured specifically to take advantage of an axle disconnect feature which reduces noise, fuel consumption, vibration, braking distances, wear, heat.... by allowing a lot of heavy and fast spinning stuff to remain stationary while you drive down the highway in 2wd. This system is dependent on having an open front differential and that may itself be the reason Ram welded the ring gear on the carrier in these trucks. If you install certain types of differentials other than open in there without otherwise compensating for it you'll make a lot of heat and noise & most likely start turning your gears & bearings into glitter over time. Not because the whole front diff is spinning, that itself isn't a problem but because it's engineered to be driven primarily from one side of the gear teeth and the back side of them is weaker both at the teeth themselves and in the case geometry, and they make heat when driven backward since they're not lapped/mated pairs in that direction.

So to compensate for that if you did somehow equip an LSD in the front carrier you would need to also modify or replace your transfer case to put you in an all-wheel-drive mode 100% of the time, ensuring that the front diff is always driven forward instead of being dragged forward.

 

[crazykid1994]

For almost everything faster than a crawl a geared (Torsen or similar) LSD is going to be better than a locking diff or a clutch LSD because it is always engaged to its full capacity - in other words there is no transition from disengaged to engaged, or from partially loaded to fully loaded, or from slip to response as you'll find with a locking diff, a clutch LSD or traction control (respectively).

For the following talk I'm going to assume no special tricks by the driver, no traction control, and 2 wheel drive - this is to keep it simple and focused on the differential's direct action alone.

A helical LSD is never trying to behave as a full lock and so as long as your driven wheels have more traction on the ground than the gears have friction on each other inside the carrier it will always allow both driven wheels to receive torque at differing speeds. That means it is equally effective while going around corners and this is why you'll occasionally see performance road cars with this kind of diff - at least historically. (Note that it will still effectively "lock" when you're on an extremely low traction surface and apply too much throttle)

The down side does come in when you are crawling on very uneven terrain and lift a tire, or when you need an awful lot of torque on a slippery surface like drawing a boat up a slick ramp or pulling a trailer on a wet dirt road (or retrieving a parked trailer on a dirt lot... you get the idea) . The left and right driven wheels on a geared LSD need to have around the same traction as each other.. like within a range of ratios. This ratio range varies by LSD manufacturer and varies to a lesser extent with lubricant type but generally it's somewhere between 3:1 and 6:1. If the difference in traction between the left and right is greater than that ratio it's just going to act like an open differential.

To put that in real terms if you are on a slick road and your left wheel has enough traction to give you 200 lb of thrust and your right wheel has enough traction to give you 100 lb of thrust, the most total thrust you can get with an ordinary open differential is 200 lbs, 100 from each wheel. If you had a helical LSD the ratio between the left and right is 2:1, that's within its range of ratios so in the same situation you could get 300 lb of thrust (200 from the left wheel and 100 from the right wheel). If you're stuck enough to need more than 300 lb of thrust it would just spin both wheels.

Now change the situation, if you were in a "V" shaped ditch at an angle with two diagonal wheels in the air you might have enough traction with one tire for 1000+ lb of thrust but the opposite wheel is dangling in the air. On both an open differential and a helical differential you're going nowhere because any number is an infinite ratio from zero. Even if you only need 50 lbs of thrust to get moving, 50:0 is a much bigger ratio than 6:1, the helical diff is just going to act like an open diff. Meanwhile a clutch LSD with preload will supply that 50 lbs to both sides because for any amount of torque less than the preload it's basically a spool. And of course if you had an automatic or selectable full locker well obviously that's able to direct full torque to a single wheel when engaged.

To summarize on a helical LSD:

Pro: Seamless, proactive torque distribution while moving including when applying power around a corner - this makes it a very smooth and addictive driving experience 99% of the time.
Con: Becomes either an open differential or a spool under the most extreme conditions (specifically when either of those is NOT the thing you want) such as glare ice or rock crawling

Another aspect of any active or torque-distributing differential is how it plays with traction control and vehicle stability control. First with traction control, as it turns out they all play very nicely with that and in fact traction control amplifies the best attributes of both clutch and helical LSD's and it does this without having to be told it's there.

Vehicle stability control is a different animal. If you had a large safe playground covered in loose gravel, accelerate above ~25mph or so and begin sawing your steering wheel left and right (this is hypothetical, I am not advising anyone to actually do this, usual internet disclaimers don't be an idiot) any modern vehicle with stability control will begin individually braking your wheels while reducing throttle to prevent a spin-out or roll-over. This could become a problem if you install a LSD because now braking input from either side would be necessarily transferred across the axle. If the manufacturer is expecting this (as in Raptor) they would naturally encode the behavior to account for that but it would be impossible for an outsider to predict how this would differ on a vehicle not originally designed to have that kind of differential. My instinct would tell me "not much" and in particular not much on a rear axle but in collisions lives are lost or saved by mere inches so it's all worth taking the time to think about.

One last note on this is the front axle. The way that the front axle is built on 1500's it is manufactured specifically to take advantage of an axle disconnect feature which reduces noise, fuel consumption, vibration, braking distances, wear, heat.... by allowing a lot of heavy and fast spinning stuff to remain stationary while you drive down the highway in 2wd. This system is dependent on having an open front differential and that may itself be the reason Ram welded the ring gear on the carrier in these trucks. If you install certain types of differentials other than open in there without otherwise compensating for it you'll make a lot of heat and noise & most likely start turning your gears & bearings into glitter over time. Not because the whole front diff is spinning, that itself isn't a problem but because it's engineered to be driven primarily from one side of the gear teeth and the back side of them is weaker both at the teeth themselves and in the case geometry, and they make heat when driven backward since they're not lapped/mated pairs in that direction.

So to compensate for that if you did somehow equip an LSD in the front carrier you would need to also modify or replace your transfer case to put you in an all-wheel-drive mode 100% of the time, ensuring that the front diff is always driven forward instead of being dragged forward.

Now I’m confused. I’ve been looking at the trutrac for my off-road/camping setup. Truck is a highway truck with mild off-roading. Should I wait for Eaton to release the e locker or would the trutrac be fine? Mud and gravel with occasional rock and other hard off-roading. Currently have the factory lsd but my tires are super heavy and it’s easy for me to power through it in mud on road. The lower traction situations off-road it seems to still work but not as well as stock tires did. I have 305/70r18 on 18x9 for reference. Combined weigh 101lbs each

 

[kurek]

Everything has trade-offs so there's no single perfect answer.

If you're not lifting tires off the ground a lot (at low speeds) or driving frequently on ice roads with unstudded tires then a helical differential is a really good piece of kit and you will not often encounter any of its shortcomings.

As you might have guessed a clutch LSD does have a maximum torque transfer value, short of catastrophic failure a geared differential does not.

But that value should be.. uh let's say generous, I would absolutely not expect anyone to encounter that limit on a frequent basis unless they're basically just mud bogging 38's or something equally extreme.

If you are noticing a reduced effectiveness of the factory LSD after a tire change I'd start by looking for other possible faults; example if you did not update your vehicle's calibration for a larger than stock tire size then traction control would not become aware of a slip as early - remember that BLD is active even when traction control is in partial off mode and when it's working properly BLD is what loads your factory, non-preload LSD in the first place so generally speaking no BLD = no LSD on these trucks even if the LSD is in fact there. Also the service grade of the gear oil (not the level of manufacturing quality, I mean the suitability of that particular lubricant) and presence or absence of friction modifier come into play, for example if you use a gear oil that comes with friction modifier in it by default and then you add even more friction modifier on top of that you've just drastically reduced the maximum torque transfer that the clutches can provide... it's just too slick now.

One part you don't really have any control over on tire size is just basic geometry.. even if you update the truck's calibration to know what size tires you have that doesn't change the number of teeth on your wheel speed sensors so now the distance you cover in a radian is greater, or the speed your wheel is turning in radians-per-second (or whatever metric you're using to measure the same thing) for a given road speed is lower and that is going to always delay the onset of any reactive mechanism. No way around that unless you're going to add teeth to your ABS tone rings in exact proportion to the tire size increase

 

[knightjp]

@kurek thanks for the input. The Ford Raptor has a torsen front diff and also has a 2H mode in its drive selector which probably means 2wd in its transfer case. I don't know much about this stuff and I admit it. So could you explain about how they manage that? (Just for my own knowledge)

@crazykid1994 Well, switchable lockers are better than LSD I suppose when it comes to serious off-roading. I think that an E-locker is already available, because the 2017 Ram Rebel had one. Not sure which brand it was.
The Military Humvees have torsen diffs and there is a trick to getting them to lock up on serious off-roading - even with wheels in the air. The video above covers that.

The video I posted does mention that the most common combo for many off-roading trucks is to have an E-Locker in the front and a Torsen style in the rear.
For me, I was just thinking that if Torsen diffs were good enough for the military in the Humvees over many kinds of terrain, then they would have been perfect for my application as well - especially because my off-roading is light.

 

[crazykid1994]

Everything has trade-offs so there's no single perfect answer.

If you're not lifting tires off the ground a lot (at low speeds) or driving frequently on ice roads with unstudded tires then a helical differential is a really good piece of kit and you will not often encounter any of its shortcomings.

As you might have guessed a clutch LSD does have a maximum torque transfer value, short of catastrophic failure a geared differential does not.

But that value should be.. uh let's say generous, I would absolutely not expect anyone to encounter that limit on a frequent basis unless they're basically just mud bogging 38's or something equally extreme.

If you are noticing a reduced effectiveness of the factory LSD after a tire change I'd start by looking for other possible faults; example if you did not update your vehicle's calibration for a larger than stock tire size then traction control would not become aware of a slip as early - remember that BLD is active even when traction control is in partial off mode and when it's working properly BLD is what loads your factory, non-preload LSD in the first place so generally speaking no BLD = no LSD on these trucks even if the LSD is in fact there. Also the service grade of the gear oil (not the level of manufacturing quality, I mean the suitability of that particular lubricant) and presence or absence of friction modifier come into play, for example if you use a gear oil that comes with friction modifier in it by default and then you add even more friction modifier on top of that you've just drastically reduced the maximum torque transfer that the clutches can provide... it's just too slick now.

One part you don't really have any control over on tire size is just basic geometry.. even if you update the truck's calibration to know what size tires you have that doesn't change the number of teeth on your wheel speed sensors so now the distance you cover in a radian is greater, or the speed your wheel is turning in radians-per-second (or whatever metric you're using to measure the same thing) for a given road speed is lower and that is going to always delay the onset of any reactive mechanism. No way around that unless you're going to add teeth to your ABS tone rings in exact proportion to the tire size increase

My computer is recalibrated for the new tires. I feel it’s just slower to engage but that may be due to rotational speed being slower at the gears. Also I had 35,000 miles on the rear gear oil and it was very dirty. I recently just drained, cleaned, and added new gear fluid and have yet to test my lsd out. I am going tomorrow to an off-road site and will possibly have the chance to test it out again. All of my off-roading will be relatively slow and there are at times 1 or 2 wheels in the air. I am aware of the brake tap method to simulate traction

@kurek thanks for the input. The Ford Raptor has a torsen front diff and also has a 2H mode in its drive selector which probably means 2wd in its transfer case. I don't know much about this stuff and I admit it. So could you explain about how they manage that? (Just for my own knowledge)

@crazykid1994 Well, switchable lockers are better than LSD I suppose when it comes to serious off-roading. I think that an E-locker is already available, because the 2017 Ram Rebel had one. Not sure which brand it was.
The Military Humvees have torsen diffs and there is a trick to getting them to lock up on serious off-roading - even with wheels in the air. The video above covers that.

The video I posted does mention that the most common combo for many off-roading trucks is to have an E-Locker in the front and a Torsen style in the rear.
For me, I was just thinking that if Torsen diffs were good enough for the military in the Humvees over many kinds of terrain, then they would have been perfect for my application as well - especially because my off-roading is light.

It was the 5th gen rebel that got it. It’s part of the 5th gen off-road package but has not officially been released to the public as far as I know.

 

[kurek]

@kurek thanks for the input. The Ford Raptor has a torsen front diff and also has a 2H mode in its drive selector which probably means 2wd in its transfer case. I don't know much about this stuff and I admit it. So could you explain about how they manage that? (Just for my own knowledge)

I have not had my hands on a Raptor so it would be necessary to speculate. There are a few ways to handle that but I should stress these are engineering choices made before they build the vehicle and would not be applicable to a retrofit in a garage.

One way they could do it is pretty obvious... put a disconnect on both sides of the diff. Done.

Another less obvious way is by setting up the differential geometry to be run in both directions without generating more heat or noise. If the teeth are essentially non-hypoid and the pinion is inline with the axis of the ring gear then they can make a lapped face on both sides of the teeth and entirely avoid the problem of heat and excessive wear. The cost of this is they don't get to take advantage of some strength advantages in having a directional gearset, so it requires considerably more material mass to make up for it and it also means the front driveshaft is still subject to spin in 2wd which really defeats the purpose of even having 2wd unless you literally just want to do burnouts. Like if you're going to be spinning the bottom of the transfer case anyway you really might as well just be full time AWD there is no advantage to 2wd otherwise.

And a third less obvious way of setting that up would be to just use a very low (transfer) ratio helical differential, which is basically just an open differential when the (input torque) ratio is high enough. Then it would just spin the disconnected stub shaft backward exactly like it works on our 1500's and since the tire diameter is pretty big the road RPM won't be really all that high. If I had to guess, this is what they're doing but I want to remind you that I have no first hand experience with the Raptor so it really is a guess.


Edit: I just looked it up, and as it turns out they do just put a disconnect on both sides of the diff. More specifically they use what Ford calls "IWE" which is simply vacuum actuated locking hubs. Like oldschool locking hubs 30 years ago except operated by vacuum solenoids.

 

[ram1500rsm]

Truetrac will be more than fine. I moved heavy Nitto MT 35's with a front Truetrac without my issues offroad in my Jeep JKU. Definitely not the best for rock crawling though but for mud/snow conditions with both wheels in the ground it makes life a lot easier.

Trutracs have a 3:1 bias, and no clutches to burn. If you're on the trails a lot with one wheel in the air, you'll benefit the most with a truetrac cause there is no clutch to grind to force traction to the wheel in the air. Truetracs gear driven are for life as long as you keep your fluid fresh. If you want more traction then Detroit locker or selectable lockers will be your ticket.

I have no idea if my LSD is still working as it should. With 97k miles i'd say it probably needs a refresh but I'm not touching it yet. I'll wait for an elocker this year otherwise I'll look into a truetrac myself. Would be in my opinion a better replacement for the factory LSD unit.

 

[kurek]

[

The video I posted does mention that the most common combo for many off-roading trucks is to have an E-Locker in the front and a Torsen style in the rear.
For me, I was just thinking that if Torsen diffs were good enough for the military in the Humvees over many kinds of terrain, then they would have been perfect for my application as well - especially because my off-roading is light.

The value of Torsen differentials in a piece of hardware like a HMMWV is that they can operate completely independent of driver input. Remember that recruits are often young men and women who may not have lived an outdoorsman lifestyle before enlisting and they really don't need "how and when to use a locker" added to their syllabus. And in a theater of war nobody needs extra levers and switches, they don't need extra maintenance and wear parts like clutches.. a helical LSD is a perfect fit simply because of its transparency.

The reason a civilian vehicle might benefit from a selectable locking differential in front instead of a torsen or clutched LSD is because any type of LSD will have a tendency to plow a little on ice and at worst that's unsafe but even at best it's kind of frustrating. Even an auto locker (like Detroit) in the front can be really annoying in the snow.

 

[crazykid1994]

I have not had my hands on a Raptor so it would be necessary to speculate. There are a few ways to handle that but I should stress these are engineering choices made before they build the vehicle and would not be applicable to a retrofit in a garage.

One way they could do it is pretty obvious... put a disconnect on both sides of the diff. Done.

Another less obvious way is by setting up the differential geometry to be run in both directions without generating more heat or noise. If the teeth are essentially non-hypoid and the pinion is inline with the axis of the ring gear then they can make a lapped face on both sides of the teeth and entirely avoid the problem of heat and excessive wear. The cost of this is they don't get to take advantage of some strength advantages in having a directional gearset, so it requires considerably more material mass to make up for it and it also means the front driveshaft is still subject to spin in 2wd which really defeats the purpose of even having 2wd unless you literally just want to do burnouts. Like if you're going to be spinning the bottom of the transfer case anyway you really might as well just be full time AWD there is no advantage to 2wd otherwise.

And a third less obvious way of setting that up would be to just use a very low (transfer) ratio helical differential, which is basically just an open differential when the (input torque) ratio is high enough. Then it would just spin the disconnected stub shaft backward exactly like it works on our 1500's and since the tire diameter is pretty big the road RPM won't be really all that high. If I had to guess, this is what they're doing but I want to remind you that I have no first hand experience with the Raptor so it really is a guess.


Edit: I just looked it up, and as it turns out they do just put a disconnect on both sides of the diff. More specifically they use what Ford calls "IWE" which is simply vacuum actuated locking hubs. Like oldschool locking hubs 30 years ago except operated by vacuum solenoids.

So if someone made front hub lockers for the rams we could potentially weld the front carrier and just lock the fronts when needed? But unlikely that that’ll happen. I’m sure welding the front in our case may not be super appealing given the weakness of our front diffs

 

[kurek]

So if someone made front hub lockers for the rams we could potentially weld the front carrier and just lock the fronts when needed?

Heh sure... but if I was running a machine shop in the world's sleepiest town & it had been a month since anyone walked in the door with a job, and you came in with a wheelbarrow full of gold asking me to build you this... I'd strongly suggest you just go buy a power wagon.

 

[crazykid1994]

Heh sure... but if I was running a machine shop in the world's sleepiest town & it had been a month since anyone walked in the door with a job, and you came in with a wheelbarrow full of gold asking me to build you this... I'd strongly suggest you just go buy a power wagon.

Lol. Yea. Question wasn’t for me. Another thread going and someone asked. I actually like the open front and lsd rear setup. It does seem to work well for what I do. Hence why I was debating on swapping from the stock lsd up to a trutrac unit.
Edit: there is a 4 door wrangler in my future for more serious off-roading and camping than what I feel the truck is capable of.

 

[knightjp]

Edit: I just looked it up, and as it turns out they do just put a disconnect on both sides of the diff. More specifically they use what Ford calls "IWE" which is simply vacuum actuated locking hubs. Like oldschool locking hubs 30 years ago except operated by vacuum solenoids.

Sounds really complicated and prone to failure. I wonder how many Raptors have gone in for front diff failure.

Lol. Yea. Question wasn’t for me. Another thread going and someone asked. I actually like the open front and lsd rear setup. It does seem to work well for what I do. Hence why I was debating on swapping from the stock lsd up to a trutrac unit.

A Ram can be a really great overlanding, camping rig. Just watch this..

Honestly according to the video about the diffs, the guy says that the Torsen/Truetrac is a much better alternative than the stock clutch type LSDs and would be a great upgrade.
If the truetrac is available of the 4th Gen Ram, I would get it.

 

[kurek]

Sounds really complicated and prone to failure. I wonder how many Raptors have gone in for front diff failure.

it's a splined sleeve, a spring, a hose and a solenoid.. I don't know how often they fail but I checked out a disassembly video and it looked like a larger diameter (stronger) version of the CAD that's on Rams and most other 4wd's.. Just built i to the knuckle instead of the carrier housing

 

[knightjp]

it's a splined sleeve, a spring, a hose and a solenoid.. I don't know how often they fail but I checked out a disassembly video and it looked like a larger diameter (stronger) version of the CAD that's on Rams and most other 4wd's.. Just built i to the knuckle instead of the carrier housing

Then it sounds like something more bulletproof than what is on the Ram. I guess that is the reason for this article.
https://www.fourwheeler.com/news/features/10-ways-2020-ford-f-150-raptor-beats-2021-ram-1500-trx/

 

[kurek]

Then it sounds like something more bulletproof than what is on the Ram. I guess that is the reason for this article.
https://www.fourwheeler.com/news/features/10-ways-2020-ford-f-150-raptor-beats-2021-ram-1500-trx/

Oddly enough the most interesting part of that article for me is this right here:



To some extent an active transfer case would have control over this but what I'm reading is that Ram thinks the regular front axle carrier assembly is strong enough for 700+ horsepower

I like Fords so to me the rivalry game isn't really that exciting - if I was in charge of Ram I wouldn't have even bothered with the rivalry angle. Think about it if you see another man or woman doing well do you run over and stand next to them wearing a "F this guy -->" T-shirt or do you give them a high 5 and keep being awesome independently? Anyway I guess that's philosophy and we're here talking steel.

In terms of steel philosophy there could be some other reasons for the differences, like if Ram decided early on this just isn't going to be sold as a rock crawler it's too wide to work seriously in that capacity they might have decided a fancy front differential just doesn't add anything to the machine. If their AWD biases toward rear-wheel-driven dynamics it may not even matter whether the front diff is open or not - except to web wheelers like us comparing things on paper we'll never own . Maybe they figured those in-knuckle disconnects on the Ford are too heavy and they rather keep unsprung weight down as a handling strategy - or maybe Ford has too many patents on them it's not worth fighting .. could be all sorts of reasons.

Like I mentioned earlier in the thread occasionally a front limited slip can be a handicap on extremely slick surfaces, they may have decided the juice ain't worth the squeeze there too.

I think it's interesting to see the differences in how each manufacturer addressed the particular market niche they were aiming for - they probably could have just thrown long travel suspension and fat fenders on the basic truck, maybe tune it for 10 extra horsepower and sold the same number of them. Starting in 2011 Dodge/Ram did offer the "Ram Runner" package as a dealer installed option but I don't think I've ever seen one in the wild; maybe a marketing failure? I think it was about a $13k option which was mostly long travel suspension, fenders, wheels, tires and a high clearance bumper. If you add those up and include installation and the fact that it's financed into the purchase it's really not a terrible price.

 

[knightjp]

I don't think that the price of the Ram Runner was much of an issue. Personally, the Ram Runner was a good package, but in a comparison video with the Raptor, the only thing that the Runner excelled over the Ford was the high speed straight running in the desert. It seems that when it come to other stuff, according to the tester, the Ford felt more composed.
I think that another thing where the Runner failed was in the design. The Ford looks like a truck that you can buy and maybe park outside a 5 star hotel. The Runner looks like a racer, especially with that front bumper situation and those awful front fenders. Makes it look like a dune buggy or a toy than a luxury vehicle.
Some people like that, but when it comes to the majority of the population, the Ford looked like a cohesive everyday driver package.

When the TRX concept came out, that was when finally Ram had something with the Runner's capabilities, but the looks of something that you would want to buy.

Honestly, I would take the TRX concept over the production version any day. It look better IMO.

Getting back to the topic, Ford's front diff situation is pretty ingenious; if it actually works well and is reliable. Getting to my initial question, a torsen/ truetrac would be an upgrade over the stock LSD and with the info in this thread would be great for my purposes. However I like the idea of choosing once and choosing well. I want to run the same on both diffs so if I can't have a Torsen in both, I will choose to have a selectable locking diffs and I am leaning towards the Cable lockers with the Electric Actuated Shifter (button) like the ones from OX.

 

[62Blazer]

Some of the above posts trying to explain the difference between LSD, Torsen, locking diffs are really confusing and not accurate....a good part of it is the definition of the terms they are using.

Torsen is a particular kind of limited slip differential (LSD). LSD's can be gear based (torsen), clutch based (preload with springs, cam actuated, electronically controlled, etc..). In general a LSD is just that, limited. This means it can only compensate for so much traction difference between the left and right side tires. For example, if the tire on one side is off the ground and the other planted on pavement most limited slips will not transfer enough power to the one of the ground to get the truck moving. There are different levels of LSD diffs in regards to how well they transfer power side to side. Most factory versions are pretty mild meaning that it doesn't take much traction difference between the tires before one side will just spin, where as on the other hand there are aftermarket versions with various degrees of aggressiveness. The reason for this is that there are some handling and driving issues with aggressive LSDs. This can be anything from tire chirping in corners to the rear end wanting to slide or spin out in corners. LSD style diffs are preferred for on-road use. Mild factory installed versions usually are good enough to prevent the "one wheel peel" leaving a stop light or will keep both tires spinning wet grass, but in heavy mud or twisting the truck up slightly will over power it and leave one side spinning. As the video stated above some times you can "fool" a LSD in transferring more power by dragging the brakes. I ran a front clutch (more aggressive) front diff and a Tru-Trac torsen rear diff in my off-road truck for several years. You had to drag the brakes quite a bit to get them to lock up. In this same truck I've had LSD front and rear, full locker rear and LSD front, and then full lockers front and rear.
Locking diffs generally refer to the type of differential that solidly locks the left and rear tires together regardless of the traction difference. These can be automatic style like a Detroit Locker (if you are coasting the tires "unlock" and allow some differential between them, but as soon as you hit the gas they lock together), or selectable that you hit a button and they lock solid. You will always have both tires turning at the same speed in any situation. These are definitely preferred in heavy off-road situations.
When I compare a standard open differential, LSD, and full locking differential I like to use this scale of 1-10, with 1 being the lowest ability to transfer power to both wheels to 10 being the best:
1=standard open diff
3 to 5 =typical factory LSD
4 to 7 = aftermarket LSD
10 = full locking diff

 

[Wild one]

Sounds really complicated and prone to failure. I wonder how many Raptors have gone in for front diff failure.


A Ram can be a really great overlanding, camping rig. Just watch this..

Honestly according to the video about the diffs, the guy says that the Torsen/Truetrac is a much better alternative than the stock clutch type LSDs and would be a great upgrade.
If the truetrac is available of the 4th Gen Ram, I would get it.

Check with Matt at Moes,a vendor on here.He can hook you up with a ZF specific True Trac.They've been available for awhile now.