I am hoping somebody would be able to come up with some ideas as to what is going on with my tow vehicle when it is in 4 wheel drive.

It has auto hubs and I am wondering if it might be the problem.

Ok here goes, in 2 wheel drive the Tahoe drives fine, but when I push the button for 4 hi, you can hear a loud clunk as it engages, then I will hear a really loud whining, and every so often the Tahoe will jerk to the right or it will jerk to the left, it also feels very sluggish when I accelerate. I think it might be a problem with the hubs not engaging all the way or a number of things. I took it to a shop and they charged me $328 dollars to tell me that I need to change the oil in the transfer case and the front differential.

You do not have hubs at all. The axle shafts turn all the time. Are you using the 4wd on the dry street?

You do not have hubs at all. The axle shafts turn all the time.

Ok, I did not know this. This happens all the time, on snow, dry pavement, mud.... and so on.

so, that would mean that it is probably the front diff?

Go ahead and change the fluids and make sure you put the correct fluid in the t case. I think there is an updated fluid recommendation from factory specs, at least thats what I was told on my 00

Yup, I'd say change the fluid to be safe. In the front diffs they use dino oil, but I put synthetic in mine. GM sells "grape juice", but it's only for rich people at almost $40 a quart. If that doesn't help, there is an encoder motor in the tranfer case that goes bad alot and kinda sounds like what it might be. It is pretty expensive to fix though, probably a $400-$500 part and $300 or so labor from the stealer. Looks pretty involved to do at home too.

check the tcase fluid. It should be blue if your truck has the auto 4wd button and the auto-trac transfer case. If it isnt go to the dealer and get GM auto trak II fluid and it isnt that expensive like 13 bucks a quart last time i bought some. And then change the tcase fluid and give it a try.

I had a similar bucking jerking problem with my tahoe and a simple tcase fluid change solved my problem.

I have already changed the fluid in the transfer case and in the front and rear differential's. I was unable to get the needed fluids at the my local parts store and was only able to obtain it from the dealer. Changing the fluids did not fix the problems.

also on another note, I keep getting the message Service 4WD on the message display. but when I took it in all the shop all they told me to do was to change the fluid and I had already done that.

The service 4wdr light is an idicator that there is a diagnostic code for the transfer case module stored. You need to know what that code is and go from there. Do the lights on the push button switch appear to work normally?
was the oil in the front diff really grey when you changed it? Front diff side bearings/pinion bearing failures are very common.

4 hi, you can hear a loud clunk as it engages, then I will hear a really loud whining .


A little help for ya here buddy: Transfer cases (push buttoms probably more noticable) will make a loud clunk when engaging 4 high or 4 low or from 4 to 2 wheel drive. That clunk is the sound of gears engaging/disengaging and the associated drive motor.
Don't drive 4 wheel drive on dry pavement. No point, is dumb and not only will wear parts out quicker, but vehicles in 4WD don't have the most friendly manners on dry pavement.

Do the lights on the push button switch appear to work normally?


No, they do not, sometimes the light indicating 2wd goes out for no apparent reason.
i also noticed that after the big snow storm we got, that when I went into 4WD that the light for 4HI would dim and then get bright again, all on it's own.

As far as driving in 4 wheel drive on dry pavement - I drive once a month in 4 wheel drive on dry pavement for less than 50 yds. I do so to make sure everything is working properly. That is it, no more. I was told to do this by a mechanic.

I am however going to see if I can pull the code.

Is it bad to drive on dry pavement even for such a short distance?

Is it bad to drive on dry pavement even for such a short distance?
nope.

I replaced a lot of 4wdr switches in that year for c0327? codes I think, lights going off and for unresponsive range changes. I also think the clunk when shifting is normal.

Hello folks im new here...
Just wanted to express that I have a very similar problem. 2WD works fine especially after putting a new tranny in after 200K. I haven't used 4WD alot, now I dont use it at all b/c I cant. I understand from alot of people that the half shaft going from the Xfer Case to the Front Diff always spins 2WD or 4WD. I have changed the fluid numerous times in the front diff, NO METAL SHAVINGS... But this winter I tried using 4WD and its jerks to the right unless I reallly get into it, it will not go straight... Any ideas? I am assuming its something to do with the front diff, are there any test I can do? Also I have no codes, or MIL's for 4WD...

Hope someone can help


John