Noisy transfer case?

[sprucegoose]

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?

[sprucegoose]

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.

[maintainin76]

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?

[maintainin76]

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???

[sprucegoose]

Originally Posted by maintainin76

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!

[maintainin76]

Originally Posted by sprucegoose

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.

[sprucegoose]

Originally Posted by maintainin76

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...

[maintainin76]

Originally Posted by sprucegoose

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.

[maintainin76]

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.

[sprucegoose]

Originally Posted by maintainin76

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...

[sprucegoose]

Originally Posted by maintainin76

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!

[maintainin76]

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

[sprucegoose]

Originally Posted by maintainin76

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!

[maintainin76]

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.

[jude240]

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.