Regear and stall TC or trade in for 8 speed.

[NOV87]

Just looking for advice. I have 2014 5.7, quadcab, 6speed, 3.55 axles, 4x4 with 30k miles on it. Stock 20" wheels with 33" tires. Would like it run like a HEMI should run. Daily driver 50/50 city/hwy.

First option:
Replace both diffs with 3.92 (4.10 would be best, but much more expensive and PITA to do) and 2600 stall Torque converter. Total with labor about $4000 -45000. Not sure how much will that affect MPG's. I'd be Ok with ~2mpg hit.

Second option:

Trade in for an 8speed truck with similar mileage. I figure, I'd be out $8k or so. Most likely the diffs would be 3.21. Probably slightly better MPG's.

I keep my vehicles for about 10-12 year. So that would be a longer investment. What would you do?

 

[NOV87]

Fat fingered my own thread, sorry.

 

[MoparBrent]

Just curious if you are considering on one hand upgrading your current diffs to 3.92. Why even consider buying a new truck with 3.21’s again?

IMO the 8speed with 3.92’s is the best way to go if your willing to trade up

 

[NOV87]

Yes, 8 speed 3.92 would be awesome! That's not what I am asking.

My current truck is 6 speed with 3.55. I like everything about it, except that it's pretty sluggish. So, the question is: would regearing to 3.92 and adding Stall TC be a good long term solution? Or, would I be better trading it in for used one with 8 speed in it. I would be getting a low mileage used one and they come standard with 3.21 gears. There are not too many used 8 speed 3.92 ones out there.
Yes, one can order a new truck with lower gears, but I am not looking to buy a new truck.
Another words:

Truck #1: 6 speed with 3.92 + 2600 Stall TC. Stock tire size. Quad cab. 4wd.
Truck #2: 8 speed with 3.21. Stock tire size. Quad cab. 4wd.

Would they be pretty comparable in acceleration from stop and acceleration in general, torque wise, etc?

 

[RLJ10X]

Why would 4.10s be more expensive?

Do a LSD if you regear.

Everybody is different, but I like my Tuned 4.10/545RFE better than the 3.21/8 that I test drove.

Get with Matt @ Moe's for parts if you regear.

 

[Wild one]

Why would 4.10s be more expensive?

Do a LSD if you regear.

Everybody is different, but I like my Tuned 4.10/545RFE better than the 3.21/8 that I test drove.

Get with Matt @ Moe's for parts if you regear.

The ZF front diffs only go to 3.92,so to go to 4.10's he needs to hunt up the earlier 8.25 AAM frontdiff and front driveshaft and the corresponding brackets to bolt it in,plus pay a shop to install a set of 4.10's in it,as no factory AAM front diff ever had 4.10's in it.You can usually find a used ZF 3.92 geared front diff for a couple hundred bucks,and install it in a couple hours on your driveway,as it's a pretty easy swap,4 bolts on the driveshaft,pop the axles out and unplug the actuator then it's only 7 bolts holding the diff in place.

 

[Wild one]

Yes, 8 speed 3.92 would be awesome! That's not what I am asking.

My current truck is 6 speed with 3.55. I like everything about it, except that it's pretty sluggish. So, the question is: would regearing to 3.92 and adding Stall TC be a good long term solution? Or, would I be better trading it in for used one with 8 speed in it. I would be getting a low mileage used one and they come standard with 3.21 gears. There are not too many used 8 speed 3.92 ones out there.
Yes, one can order a new truck with lower gears, but I am not looking to buy a new truck.
Another words:

Truck #1: 6 speed with 3.92 + 2600 Stall TC. Stock tire size. Quad cab. 4wd.
Truck #2: 8 speed with 3.21. Stock tire size. Quad cab. 4wd.

Would they be pretty comparable in acceleration from stop and acceleration in general, torque wise, etc?

If everythings equal as far as engine mods go,the 8speed with 3.21's is still way deeper geared in first gear then the 6 speed with 3.92's is.To match the 4.71 first gear in the 8 speed,you damn near need a 5:1 rear gear with the 6 speed.You also get a way better transmission with the 8 speed,the old 5/6 speeds are notoriously light duty,and have a tendenancy to scatter parts if you start putting some power to them,and don't know how to drive them.No wide open throttle downshifts,or else you'll be replacing the tranny sooner then you want.Price everything out,and if you can get yourself into a newer truck with the 8 speed and 3.21's for close to the same money as doing the gears and torque convertor,i'd go for the newer truck with the 8 speed.

 

[Pull Ya]

I agree going to a newer truck with the 8 speed in the long run would be a better option. If you are looking for increased acceleration you might look at the Pedal Commander. It will not increase the hp or the torque of your truck but it sure will make a difference in acceleration. You might look around the site and read about them, there are a few threads about them. You can also run a tuner at the same time as a Pedal Commander and you do not have to buy a new PCM for a tuner.
Jay

 

[NOV87]

RLJ10X, I'd love to do 4.10, but too much effort needed, the Wild one summed it up pretty good. Yeah, a few things to consider Thanka to everyone for you opinions!

 

[RLJ10X]

First gear in the 5/6 is too tall, unless you have 4.10s and first in the 8 is too short. Why can't they get first gear right? I remember first gear with 3.55s was like starting out in second gear.

The 5/6 isn't nearly as bad as W1 makes it out to be. Just dont drive like a 17 year old, and you'll be just fine. The 8s aren't totally trouble free. But they are the better of the 2, until it's time to change the fluid. The money you saved by getting that extra 1 mpg just went ****! when you change fluid in an 8.

DO NOT get a 3.21 rear end in anything. If you do swap trucks, shop around until you find a 3.92. They're out there.

 

[NOV87]

The 5/6 isn't nearly as bad as W1 makes it out to be. Just dont drive like a 17 year old, and you'll be just fine. The 8s aren't totally trouble free. But they are the better of the 2, until it's time to change the fluid. The money you saved by getting that extra 1 mpg just went ****! when you change fluid in an 8.

DO NOT get a 3.21 rear end in anything. If you do swap trucks, shop around until you find a 3.92. They're out there.

Is it even worth swapping 3.55 to 3.92? Also, what's everyone's opinion of Stall TC for daily driving? Thinking of 2600 one

 

[clint440]

I have a 8 speed 3.92 crew cab and for daily driving when not trailer towing or drag racing, I think it's a little over geared. Never driven a 3.21 8 speed or the old 545-rfe for comparison but I think a 3.55 or a 3.73 would be a better all around set-up with the 8.

That said if you aren't too attached to your current truck and can reasonably get into 8 speed anything ram, you will be impressed. It's a very smooth, quick shifting transmission also used in a lot of different platforms outside of chrysler.

To unleash the power of the hemi, you should try tuning it. In your case you won't need an unlocked PCM and a generic diablo canned tune will wake it up. It's much more than you think possible for a naturally aspirated truck. It woke up mine, went from grain truck to muscle car in terms of response and not being held back.

Just a $300 to $400 investment vs upgrading parts or getting a newer pickup.

 

[Pull Ya]

IMHO a gear swap from 3.55 to 3.92 would not be worth the money spent. I had a 13 with the 6 speed and 3.92 gears and I added a 2600-2800 Edge TC and it did not have a negative effect on daily driving. I also had other supporting mods ie; Vararam, larger TB, and tuner. It ran pretty good for a 5000lb brick.
Jay

 

[NOV87]

I like what I hear
If I keep the truck (most likely), will do the TC and see how that does and then probably Diablo tuner. Would like to do hardware before the software.

 

[HammerHead]

Your better off going with a higher stall TC and a good custom tune. The 3:55 to 3:92 won't be what your looking for; I went 355 open diff to LSD and 410's. Money well spent but not what I thought it would be, wished I had went with 4:56. But mine was a 2x4.
If you do go the TC route then a Limited Slip Diff is a must, or you'll just burn the right rear tire off.

Save your money a skip the re-gear; get a TC, LSD and some fat Nitto rubber and enjoy your rig.

Over 4 years I dumped 10k into my 2013 5.7 with the 6 speed trying to make it fast, mostly on repairs and low life mechanics. Just to have a bone stock 5.7 with 8 speed tranny or a ford eco-boost Blow my Doors OFF.

 

[Wild one]

First gear in the 5/6 is too tall, unless you have 4.10s and first in the 8 is too short. Why can't they get first gear right? I remember first gear with 3.55s was like starting out in second gear.

The 5/6 isn't nearly as bad as W1 makes it out to be. Just dont drive like a 17 year old, and you'll be just fine. The 8s aren't totally trouble free. But they are the better of the 2, until it's time to change the fluid. The money you saved by getting that extra 1 mpg just went ****! when you change fluid in an 8.

DO NOT get a 3.21 rear end in anything. If you do swap trucks, shop around until you find a 3.92. They're out there.

The 3.21's aren't near as bad as you portray RLJ,lol. Around town with the 8 speed,they still provide better acceleration then a comparable 5/6 speed truck with 3.92's,and once you're on the highway,they really shine.I know of a couple 4X4's that run mid 12 second 1/4 mile's with 3.21's. It depends on what your style of driving is like,if you do any freeway driving the 3.21's return better gas milege,and around town,the diferance in milege is still in favour of the 3.21' on an unloaded truck. I love getting 3.92 geared buddies on the freeway,after an hour at 85+ mph,they're whining and want to slow down as their oil temps are through the roof,lol

 

[RLJ10X]

What size tires are the guys racing 3.21, on?

 

[Wild one]

What size tires are the guys racing 3.21, on?

One guy is on 33" tall 22's,and the other one is on honking huge 12.50 35's on heavy assed -44 Fuel rims,lol. There's a few guys drag racing the 3.21 geared trucks,and even the bolt-on guys are deep into the 12's. Comparing apples to apples,a 3.21 geared 8speed truck with the same mods as you have on your tuned 3.92 geared 5 speed,is gonna kick your trucks ass to the curb,and leave you wondering why you have a 5 speed with 3.92's,lol
My 4x4 went 12.50's with 3.21's went to 3.55's and it still went 12.50's,only thing is it shifts out of first gear before the 60ft mark now.My fastest 60ft time was done with 3.21's ,as the truck was pulling first gear past the 60ft mark,and wasn't shifting into 2nd.

 

[RLJ10X]

I certainly would be wondering why I had 3.92s




I have 4.10s


Racing in an exercise in futility. There is always somebody faster.


Why did it take an 8 speed until earlier this year to break Matt's record with his '11 ?

 

[Wild one]

I certainly would be wondering why I had 3.92s




I have 4.10s


Racing in an exercise in futility. There is always somebody faster.


Why did it take an 8 speed until earlier this year to break Matt's record with his '11 ?

Nobody lightened a truck as much as Matt did,lol. What 5/6 speed bolt-on truck has ever come close to matching Kyle's 11.98 with a 8 speed bolt-on truck,lol. In comparable basically stock bolt-on trucks,the 8 speed is usually a full 1/2 sec faster over the older 5/6 speed trucks,and you can wide open downshift it with-out scattering it on the pavement,lol.
An 8 speed with 3.21's and comparable mods is still gonna blow your 4.10's into the weeds,and pass you with another 20 mph wide open,lol