Does A 4WD Truck Need Limited Slip

[Bike_Pilot]

It may be that the trucks you are looking at have it as a standard feature. A locking rear diff was standard on my '18 3500 SRW diesel. I added an ARB air locker to the front so I can be fully locked with all four turning if I want.

As to whether it's necessary or not it really depends on your uses. The more you find yourself in situations with very limited traction or a wheel of the ground the more important it is. These trucks are really heavy and have stuff suspension, so on steep, uneven terrain it doesn't take much to unweight a wheel and lose traction on that wheel.

You can add lockers as aftermarket. Figure on 1100 for parts per diff.

 

[TestPilot57]

Okedoke, I already commented on this at least once if not more...

Bottom line? Here are the three answers that apply to ALMOST any question.

Yes.
No.
Maybe So.

The "Maybe So" answer is where it can get complicated, and in this question (as in most/all) that answer depends on what your expectations are.

 

[fireflymedic]

My thoughts on this is your buying 4 wheel drive to not get stuck and paying slot for that feature up front and forever with poorer fuel milage. Limited slip also helps you not get stuck. It is cheaper and does not drop your fuel milage. So yes get it. You know without it you could get stuck with 2 tires on pavement. Shameful if this was to happen your only half off the road yet stuck.

 

[TestPilot57]

Whoever wrote that isn't really what i'd call up on how things work with comments like this....

Can you point me to your commercially supported website with a better technical explanation of how it works? Or, even better, an article in terms a redneck could understand?

Signed,
Redneck Dev

 

[Travelin Ram]

My thoughts on this is your buying 4 wheel drive to not get stuck and paying slot for that feature up front and forever with poorer fuel milage. Limited slip also helps you not get stuck. It is cheaper and does not drop your fuel milage. So yes get it. You know without it you could get stuck with 2 tires on pavement. Shameful if this was to happen your only half off the road yet stuck.

That is never going to happen in any modern 4x4 with traction control.

 

[ramffml]

That is never going to happen in any modern 4x4 with traction control.

Exactly. Excluding offroading, the amount of situations one can get into in a modern 4x4 truck that absolutely requires a LS to get out of, has to be close to zero. Might take a tiny bit more effort without, but really, "need"? No. Nice to have? Yes.

 

[Wild one]

Can you point me to your commercially supported website with a better technical explanation of how it works? Or, even better, an article in terms a redneck could understand?

Signed,
Redneck Dev

I did explain it,in laymens terms,but i can't help it if you don't understand how an open diff works

 

[ramffml]

Can you point me to your commercially supported website with a better technical explanation of how it works? Or, even better, an article in terms a redneck could understand?

Signed,
Redneck Dev

Take a 2wd drive truck with open diff and jack one wheel fully in the air and turn of all traction controls. Put it in drive and rev it up, does the truck move at all? My guess is it won't move an inch. I've seen this demonstrated a few times (instead of jacks they used rollers, same idea).

We can talk about torque until the cows come home. Bottom line is, without traction control, an open diff will stop your truck from moving the second one of your two wheels loses traction. However traction control is so good these days that if its enabled it will brake the spinning wheel, causing the torque to flow to the wheel with traction. In the past before TC we just used to apply a bit of brakes manually while giving it some gas to get the same effect.

 

[Travelin Ram]

How do you explain a block long one wheel blackie on the pavement then,otherwise known as the one wheel peel,the vehicle is definitely moving to.I've had cars that'd roast one tire at 50 mph pretty easily,curious on how you explain that scenerio if both wheels are getting the same amount of applied torque to them.I'll admit they have the same applied torque till one wheel is spinning,then i think the spinning tire is getting the majority of usable engine torque

Where your example breaks down is in the conflation between torque and HP. Yes, an open diff guarantees equally applied torque. Say, just for the sake of example it takes 1,000 lb-ft to maintain slippage at the roasting tire. So the same 1,000 is applied to the gripping tire on the other side.

Now HP on the other hand, is the product of torque and RPM. So, if the spinning tire is turning 3x the revs, it is consuming 3x the power. In which case 25% of the net power is on the slow tire, and 75% on the fast tire. Ergo the smoke.

 

[Wild one]

Where your example breaks down is in the conflation between torque and HP. Yes, an open diff guarantees equally applied torque. Say, just for the sake of example it takes 1,000 lb-ft to maintain slippage at the roasting tire. So the same 1,000 is applied to the gripping tire on the other side.

Now HP on the other hand, is the product of torque and RPM. So, if the spinning tire is turning 3x the revs, it is consuming 3x the power. In which case 25% of the net power is on the slow tire, and 75% on the fast tire. Ergo the smoke.

I refer back to my example of using 2 hub dyno's to measure torque output at the wheels.The only dyno that's going to give you a torque reading is the 1 hooked to the spinning tire,the locked stationary dyno isn't going to give you a torque output reading.Dyno's read torque then compute that number to a horsepower reading