2002 Tahoe z71 rear diff question

[Jmjmjm]

Hi!

New to the forum and first time I own a GM at all. Just bought a 2002 Tahoe z71. I’ve read a lot on the forum already and learned a lot but not enough to avoid a thread now

I noticed quite fast when first putting the car in 4wd that the rear diff is definitely locked. I first tried the 4wd low and thought it might be locked when in low but tried high and it’s the same thing. I’ve understood that there are different options on these cars so it’s not always the same diff? Are they supposed to be lockable in some way? Or is mine just definitely f-cked?

After driving in 4wd and going back and forth a bit I got the “service 4wd” error message. It disappeared after restarting the car but has come back a couple of times in the last week or two.

What to check first? Open diff housing and pray? Or is there some easy check to do before that? Or is there any chance that it’s supposed to be locked? It can’t be a diff that is always locked right?

Sorry for my low level of understanding on this…

Thanks in advance!

 

[strutaeng]

Welcome!

What do you mean when you say the rear is locked? The differential acts like an open differential until one wheels starts spinning, then the G80 engages and both axles spin at the same rate. Wet one wheel on mud and the other on pavement and give it moderate throttle to test it.

The error message is probably something unrelated. Possibly the encoder motor reluctor wheel.

 

[Jmjmjm]

I mean that the diff is completely locked. If I go in a circle one wheel skips and you can feel in the steering wheel that it doesn’t want to do tight turns because it’s not open…

 

[strutaeng]

I mean that the diff is completely locked. If I go in a circle one wheel skips and you can feel in the steering wheel that it doesn’t want to do tight turns because it’s not open…

Oh WOW. That should be unrelated to if it's in 2wd or 4x4 because the rear axle only depends on getting power via the driveshaft.

Did the seller tell you about that?

I guess next step is to remove the differential cover and see what happened in there. There was a member here recently having similar issues and it turned out to be his brakes were seized or something like that. Maybe in the last month or two. Do a search.

 

[Fless]

Take a look at your RPO codes in the glovebox and you'll likely have a G80 code, which is for the rear diff. If that's not on the sticker, post up all of your Gxx codes so we know what we're looking at.

 

[OR VietVet]

Welcome to the forum from Oregon.

If this only happens when in 4wd, then I suspect that what you are feeling is not the rear but the front. It will act differently in 4wd. Does the feeling continue to happen when in 2wd? The rear diff will be independent of the front diff. When you are in 2wd, it does what it does. When you are in 4wd, it does what it does.

 

[Jmjmjm]

Hi all! Thanks for the replies! Seems to be a great forum so far.

I’m stupid enough to have been thinking it’s FWD when in 2WD. And of course that’s not the case. So I understand what you mean with the rear diff doing it’s thing in 2WD also. I’ll have to take it for another spin and give it a proper test to understand what’s happening. Because in 2WD I’d say it feels normal. The feeling could very well be the front like you say, but I’m sure the rear wheel was skipping when in 4WD so how can that be happening… I’ll test drive tomorrow and see what I can figure out.

I have the G80 rear diff according to my sticker.

 

[OR VietVet]

You are feeling the front end binding. Especially with sharp enough turns. Shout not be in 4wd on dry pavement. In mud or snow or enough wet there is slippage and less of the bind feel.

 

[Jmjmjm]

You are feeling the front end binding. Especially with sharp enough turns. Shout not be in 4wd on dry pavement. In mud or snow or enough wet there is slippage and less of the bind feel.

So you mean you think what I’m experiencing is completely normal? And the 4wd on these cars should only be used when driving on slippery roads, snow etc then? When driving it slow on dry pavement it should be really hard to make a sharp turn then I guess? Steering wheel “wants to” go back to straight if you know what I mean?

OT even if I live I Sweden I’ve been hiking around Multnomah falls in Oregon a few years ago! It’s a small world!

 

[Jmjmjm]

The only 4wd car I’ve had before was a G-wagon with lockable TC, front diff and rear diff. So that’s basically what I’m used to. And this 2wd/4wd on the Tahoe means the TC will lock (bad way of explaining since there is no TC diff but) when I engage 4wd, right? So it’s basically like driving the G with the TC diff locked and that’s what’s causing the (imo quite brutal) binding when being in 4wd, correct?