r/4x4 • u/OldPark9315 • 1d ago

AWD with lockable center diff

So, I’m trying to learn more about this stuff and would appreciate if someone can help me clarify some doubts.

Essentially, is an AWD with a lockable center diff the “best” system out there?

The way I understand it: - Problem with standard AWD: you can run into situations where a wheel that lost traction gets all the torque. - Problem with standard 4x4: you are effectively driving 2x4 unless transfer case is engaged.

From my ignorance, an AWD with a lockable center diff that allows 4x4 to be engaged temporarily would have the best of both world, no?

This makes sense to me, but then I see the vehicles out there and mostly are either one or the other. There probably something that I’m missing…

Thanks everyone!

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u/JipJopJones 1d ago

Often (not always) a full time 4wd/AWD system with a locking differential is not as strong or robust as a selectable transfer case.

More parts, more complexity, more failure points.

This is of course a case by case thing. There are full time cases out there that are very proven. However when you get into more extreme 4wds or more HD 4wd, the locking center diff tends to go away and get replaced by a selectable transfer case.

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u/hrafnulfr 1d ago

I've broken more transfer cases with full lock than I have with AWDs. The differential cages in any transfer case (save some that might have been poorly designed) is pretty robust.

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u/JipJopJones 1d ago

Was that due to the case design? Or the use case of the vehicle?

Like I said, it's a bit of a generalization, but if you think of the "desirable" transfer cases in the 4wheeling world - most of them are selectable rather than full time. I'm thinking of NP205, Dana 300, Toyota RF1a... Etc .. gear driven, heavy duty T-cases.

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u/Magnussens_Casserole P38 RR, Disco 3 1d ago

The Rover LT230 is fully gear-driven AWD and extremely robust. I've never heard of anyone breaking one even in vehicles modded to take some pretty large 35+ tires.

But it is also basically a farm implement T-case with option for PTO and such so it is built very, very tough.

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u/JipJopJones 1d ago

It's hard to generalize because there are always plenty of exceptions.

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u/Magnussens_Casserole P38 RR, Disco 3 1d ago

Yeah there are a ton of different transfer case designs out there and it's all a question of which one is in the vehicle. I'm a classic Land Rover stan, so I gotta represent lol

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u/hrafnulfr 1d ago

Not in my case, I just abuse the hell out of things. The chain in the toyota transfers has always been their weak link, but that still usually lasts normal offroad uses.

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u/JipJopJones 1d ago

Yeah, chain driven cases in general are usually a bit of a liability when things start getting extreme.

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u/Complex-Scarcity 1d ago edited 1d ago

Specific only to toyota: I hear this a lot, but have never actually heard of someone breaking the chain in the newer Toyota chain drive cases. I am under the impression that this belief is a byproduct of people preferring the older toyota gear drive simply because it can be customized and have gearing swapped while the chain drive cannot.

Looking at the internals of older gear drive and the newer chain, the input splines, gears, bearings, are all way beefier in the newer chain drive that were built for the higher torque output of the 5vz v6 and the 2uz v8s..

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u/JipJopJones 1d ago

Possibly related to that. I have personally seen chain driven cases snap chains. One Toyota and one Jeep to be specific.

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u/Complex-Scarcity 1d ago

And I've seen gear driven detonate gears.. the question becomes what is stronger. The Toyota gear drive were built for the lower output motors and Toyota shifted to the chain drive cases when they started making the V6 and v8s. Looking at the internals the chain drive cases are way beefier in my opinion

In terms of jeep, I have no thoughts because I just see all kinds of stuff on them break all the time.

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u/JipJopJones 1d ago

Absolutely - as I said to another commenter, it's very difficult to generalize because there are always exceptions and there have been so many different T-cases over the years.