Noisy transfer case?

I have a strange noise that began recently in the transfer case on my 98 Tahoe 4x4. I had it up on 4 jackstands today and it is actually more noticeable in 2wd than in 4wd. It is kind of a clicking/crunching noise. When you are in the truck you really don't hear, it unles you are driving slowly past a wall with your window down or something. Even then it just sounds like a light clicking.

It really seems weird that it would be worse in 2wd though... Overall there has always been more driveline noise at full highway speed in 4wd of course. Is the trans. case on its way out? The fluid was changed to the blue Auto Trac II once at 106K, it has 168K on it now. I am afraid to hear what I may be up against here. Anyone else experience these symtoms or repair?

Well, I drained and refilled the transfer case last night with the Autotrac II bluid fluid again. The old stuff didn't look bad at all... a little dark with some silvery slurry suspended in it, but nothing major at the bottom of the drain pan. It did have 62k on it.

It still sounds the same, and I noted I could even hear that clicking by turning the rear driveshaft while the wheels were in the air. There must be something going on in there. I did some searching on a couple Chev truck forums, and on this one there were some discussions on a c-clip type retainer breaking or falling off in the tailshaft area.

http://forums.vmag.com/suvtahyuk0301/

I believe it was a 97, or at least it must have had a different t-case as they were talking about removing the tailshaft of the case with just 4 bolts and mine only splits down the middle with like 12+ bolts...

I have a 600 mi. trip this weekend, so i'm gonna give it a shot and keep my fingers crossed. Maybe i'll run it to a shop and have them listen to it today after work.

So you can use the new AutoTrac II fluid in the older Tahoes? I have a 99 hoe with autotrac and I assume you can use AutoTrac II fluid in it? Right now it has dexron III in it. Do you have to flush the old stuff out or can you just drain and add the new?

Also since you cant just pour the new fluid into the transfer case, what did you use to fill it up? Do they sell a pump anywhere that you can use? Could they have made refilling this thing any harder???

Also since you cant just pour the new fluid into the transfer case, what did you use to fill it up? Do they sell a pump anywhere that you can use? Could they have made refilling this thing any harder???

Yes, you SHOULD be using the Autotrac II fluid! There was a Tech. Serv. Bulletin to do so from what I understood, and it ws the only thing that finally cured my dreaded cluck when pulling away from stop signs.

You drain and fill with it once, use a pump which screws right on the top of the bottles. I think I got mine at Auto Zone or Checker, I forget which. It was like $3. Then you run that around for about 1/2 hr. switching in/out of 4wd occaisonally, drain and then refill again. Should take you between 4-5 qts. for the whole process. Good luck!

Yes, you SHOULD be using the Autotrac II fluid! There was a Tech. Serv. Bulletin to do so from what I understood, and it ws the only thing that finally cured my dreaded cluck when pulling away from stop signs.

You drain and fill with it once, use a pump which screws right on the top of the bottles. I think I got mine at Auto Zone or Checker, I forget which. It was like $3. Then you run that around for about 1/2 hr. switching in/out of 4wd occaisonally, drain and then refill again. Should take you between 4-5 qts. for the whole process. Good luck!

I dont have a autozone or checkers where I'm at, just a Napa. I'll have to check and see if they have anything like that. $3 is pretty cheap. I assume it's just a hand operated pump.

I dont have a autozone or checkers where I'm at, just a Napa. I'll have to check and see if they have anything like that. $3 is pretty cheap. I assume it's just a hand operated pump.

Yes, it is just a hand-pump like on the top of a soap dispenser, just a little bigger. It has a 18" long plastic hose so that you can snake it over that cross-member to get the lube in the fill hole. Be carefull taking out that fill plug. If you still have the 1/4" square drive socket plug, it strips out easy. The replacement plug has a male 1/4" sq. drive head on it...

Yes, it is just a hand-pump like on the top of a soap dispenser, just a little bigger. It has a 18" long plastic hose so that you can snake it over that cross-member to get the lube in the fill hole. Be carefull taking out that fill plug. If you still have the 1/4" square drive socket plug, it strips out easy. The replacement plug has a male 1/4" sq. drive head on it...

Heh, funny you should mention stripping out the plug. I just made a post on that the other day. I went to the dealer and got the plug with the 18mm bolt head on it. So, just to make sure, there is only one autotrac II fluid right? It is p\n 12378508? I think I'm gonna go buy some and change it out this weekend. Thanks for your help Spruce.

I went and picked up some of the new fluid. Cost me $6.50 a quart. I wanted to ask though, did you read anywhere that you had to flush the transfer case of the old stuff completely? The guy at the dealership told me that I didnt have to flush, all I needed to do was drain the old and add the new.

I went and picked up some of the new fluid. Cost me $6.50 a quart. I wanted to ask though, did you read anywhere that you had to flush the transfer case of the old stuff completely? The guy at the dealership told me that I didnt have to flush, all I needed to do was drain the old and add the new.


Like I said earlier:

"You drain and fill with it once, use the pump (till it runs out the fill hole) Then you run that around for about 1/2 hr. switching in/out of 4wd occaisonally, drain and then refill again. Should take you between 4-5 qts. for the whole process"

One guy said his dealer told him just idling with the rear wheels off the grounbd turning for 20 minutes was sufficient. That would be a little easier, seeing as you wouldn't have to jack it up twice...

So, just to make sure, there is only one autotrac II fluid right? It is p\n 12378508?

Yup, 12378508, that's the blue juice alright... Just looked at the extra bottle I had left. Good luck on the lube change!

Did the change. Went pretty smoothly. Took exactly two quarts each time.

Did the change. Went pretty smoothly. Took exactly two quarts each time.

That's great, good news! Did yours have the infamous bump/clunk when you were pulling away from a stop light, prior to this switch/fluid change? I couldn't believe how that just totally went away when I switched to the AutoTrack II fluid! I was mad I had dealt with that clunk for over a year before finding that out!

I occasionally got a clunk, mostly after coming to a hard stop. I havent driven it that much since I changed it so I cant really say if it solved it yet. From all that I've read though, it should.

did you ever fixed that clicking problem?

If not it could be the U joints on the drive shaft. I had that problem last year. Drove me nuts, it gets louder as it gets worse.

I had this problem. There was a broken pin in the case that was causing the rattle/clunk. I say "pin" because thats what it looks like and I dont know the actual name of it, but its a BIG BOLT looking thing and its copper and heavy. Had it replaced and problem was fixed. Cost more labor to take the case down than to install a new pin.

I had this problem. There was a broken pin in the case that was causing the rattle/clunk. I say "pin" because thats what it looks like and I dont know the actual name of it, but its a BIG BOLT looking thing and its copper and heavy. Had it replaced and problem was fixed. Cost more labor to take the case down than to install a new pin.

MIkeman28: What year is yours ? The reason I asked this is there was several others talking about some pin or clip that comes loose or breaks apart, but that was in the 96-97s. This is easily fixed on those by dropping the rear driveshaft and then there are four bolts that hold the tailshaft area of the T-case on that can be pulled of to expose this clip area. Mine doesn't have this... The transfer case in the 98 is different I guess. Probably because of the Auto4wd addition I suppose. Just curious, what did this repair cost you?

Juse240: No, it still sounds the same, but doubtfull that it is the U-joints. I have replaced them all before and keep them all well lubed, with the exception of the fron shaft near the differential. Just checked tham all today in fact as I was doing a front brake job on her. It is certainly coming from inside the Tcase, cause I can hear it in there when I turn the driveshaft by hand even!

MIkeman28: What year is yours ?
97 Yukon 4x4

97 Yukon 4x4

Yup, it could have been that retailer near the tailshaft area MIkeman28, but the part your describing sounds like something else. What exactly did yours sound like when it went, and how long before you took it in for repair? What did the damages run you? Thanks!

Well, two months later and 175k miles now. The t-case is starting to click/pop more now, especially at slow speeds along side an object like a wall where the sound bounces back up at you. Daughter used the 4wd high in the rain the other day, and then of course it was left on for a couple days after that on dry pavement... ouch!! Now is crackles, pops, and crunches in 4wd really bad.

I'm thinking I'm going to have to overhaul this thing or replace with a used case now. This sucks, I don't have the time or the money to do this. Does anyone have any other suggestions or experiences like this?