Center diff vs transfer case

[4runner]

I have a general 4WD question. It is related to towing so I figured this is a good place to ask. I currently have a 4Runner with a center differential that allows me to operate in full time 4WD, or part time 4WD or 2WD. I can also lock the center diff if need be. The multi-mode system has worked well for me, and I like running in full time 4WD in winter/snow conditions, which in western New York, is longer than I wish.

I'm currently looking at my "next vehicle" and the new 4Runners have part time 4WD, as does the Tundra and most other pickups.

Why don't bigger vehicles have a center diff? Is it because the center diff is a weak link?
How do you guys who drive in snow or mixed conditions like using a part time system? Does the additional vehicle weight help traction?

Thanks.
Bob

 

[timswi]

I might be lost in the differing terms, but here's my take:

I have a GMC 1500 4x4 that has AWD, high and low 4wd and 2wd. If the weather is snow and whatever mixed, I run in AWD. If the snow is really bad, I run it in 4wd. Otherwise, it's 2wd.

On the previous trucks I've had that didn't have AWD, I'd just change between 4wd and 2wd as needed. Never had a problem.

 

[hawkeye08]

I might be lost in the differing terms, but here's my take:

I have a GMC 1500 4x4 that has AWD, high and low 4wd and 2wd. If the weather is snow and whatever mixed, I run in AWD. If the snow is really bad, I run it in 4wd. Otherwise, it's 2wd.

On the previous trucks I've had that didn't have AWD, I'd just change between 4wd and 2wd as needed. Never had a problem.

Your AWD is actually "auto" 4WD which engages front axles at differential and when slippage is detected, engages transfer case for 4WD. We run this way in the winter months on '98 yukon since black ice is common.

GM pickup and SUV AWD (all wheel drive) has a full time center differential, no 2WD available, such as the Yukon XL Denali (since about 2000).

 

[timswi]

Your AWD is actually "auto" 4WD which engages front axles at differential and when slippage is detected, engages transfer case for 4WD. We run this way in the winter months on '98 yukon since black ice is common.

GM pickup and SUV AWD (all wheel drive) has a full time center differential, no 2WD available, such as the Yukon XL Denali (since about 2000).

True on the "auto 4wd"...Got the terms wrong. The wife's Hummer runs in awd all the time, can't shut it off...Even though I wish I could.

 

[Diamondpilot]

The way I understand it a center diff like on the Mercury Mountaineer we had with AWD only allows one range.

A transfer case, like on every 4x4 truck I have owned, has the ability to have multiple ranges. In most cases its High and Low. It also allows for the selection of which output shafts get power. In most cases its usually running power to the output shaft that is connected to the rear drive shaft and gives the drive the ability to control the engage/disengagement of the output shaft that is connected to the front drive shaft.

This would give your average transfer case the selection of 2 wheel drive, 4 high, and 4 low.

Chris

 

[4runner]

I guess I picked a bad title. My 2002 4Runner has a two range transfer case too. But with its center differential, it can be run in 4wd all the time, or 2wd. They call it multi-mode.

The new 4Runners and Tundras have a part time system with no center diff. (although the 4Runner Limited and Sequoia both have center diffs and the ability to run in 4wd all the time).

I did not know that GMC/Chevy had the ability to run in full time mode. I checked the Ford F150 brochure and didn't think it could.

My real issue is whether I will be satisfied with a part time 4wd system given my winter driving conditions, and I am looking for feed back from others.

It is also related to towing because when I tow, I typically keep it in 4wd all the time too.

Bob

 

[dodge man]

I've only had part time 4 wheel drive pick ups, no center diff. Its usually not a problem for me, once in a while I will end up coming onto a paved road in 4 wheel drive, and the front and back end are fighting each other while it comes out of 4 wheel drive, but its not that big a deal.

I'm sure a center differential is just one more thing to break down, but I don't know if they are ever really a problem area or not.

 

[LD1]

I'll give you my understanding of the terms, which may be wrong.

The center diff is just like the diff in the rear axle. In the rear axle it allows one wheel to turn faster/slower than the other when making turns (in theory). But when stuck, like on ice or in mud, you only have one wheel doing any work.

The center diff is the same only it splits the fronts and rears. Under normal driving conditions, All the wheels have power and it allows you to make tight turns in 4wd without the front and rear fighting eachother due to the front making a wider arc than the rear.

The problem with the center diff is the same as a rear diff, you may only have one axle turning if you get stuck. And if that axle doesnt have a locker or limited slip, it may only allow one wheel to turn.

So hypothetically, If you nose into a mud pit/sink hole with the front axle, ad are in 4wd but have a center diff, there is a chance that you wont be putting any power at all to the back tires that have traction. And if you have an open diff in the front, only one wheel will be spinning even though you are in 4wd. This is one of the reasons true 4wd'ers dont like them. As well as they are another weak link.

A lot of newer vehichles are running center diffs to give full time 4wd but an older example is the NP203 transfer cases. They were full time cases but they had 4 selections. hi, hi-loc, low, low loc. The loc settings locked the center diff to still be able to have true 4wd. I think this is probabally what your vehichle has, but the termonoligy has changed a bit.

 

[Diamondpilot]

Ford used to offer a AWD selection and my GMC I had in 05 had it. I did not care for it. I am smart enough to decide when I need 4 wheel drive and just prefer to do it myself. The wife is a different story so she gets AWD most of time.

Chris

 

[LD1]

Ford used to offer a AWD selection and my GMC I had in 05 had it. I did not care for it. I am smart enough to decide when I need 4 wheel drive and just prefer to do it myself. The wife is a different story so she gets AWD most of time.

Chris

I have an 03 chevy that has the "AUTO" as well. I agree, I am spart enough to decide.

The big thing I dont like about it, it has to see a difference in wheel speed from front to rear (slip) to engage. By that time, It may be too late.

Last winter while plowing, I decided to us it in my drive just to see what it was like. While it does detect wheel slip rather quickly, it might not be fast enough in a real spin-out situation on the road. And the other thing i dont like about it, once the rears are spinning and it decides to engage, everything is moving and under load. Engaging the fronts with the backs already spinning and under load cant be good on components. So I dont use it at all anymore.