About two months ago I changed the fluid in my T-case. I went to my local dealer and he gave me two bottles of Autotrack, he informed me this was the only fluid GM uses in their T-cases (I now see it calls for Dex III). About a month after the change I noticed it was leaking. I have since changed it back to the proper fluid. If I clean it well and take the truck for a short drive it will appear to coming from the main seam right around one of the coated bolts that’s holds the case together. Could this be corrosion around one of the isolators? Could the Autotack have caused this (or just a coincidence), and what is the best fix?

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2001 2500 HD D/A 4x4

Autotrack fluid is not for our vehicles.IIRC it is for the 1500 series 4x4 not the HD series.

I would ask for a explanation from who ever changed it.

I am the one that changed it. . .after being told (by the parts guy) that Autotrack it the only fluid used in the tcase. Before I go back and question this I guess I would like to know if it could cause any damage. I would imagine it would lube proberly and I doubt it would cause a leak in a seal/gasket, but I can't help but wonder.

I will likely change that rear gasket and seal, can that be removed without pulling the case from the truck? (It looks as though you could slide it back far enough!?

look carefully at where the leak is coming from, make sure there is not a hole in the case, you will have to clean it well and carefully inspect to see it. Can be misleading

My 2001 2500hd D/a Lt C/c 4x4 Wood Not Go Into 4 Wheel Drive Took It To The Chevy Dealer And They Said The Transfer Case Did Not Have Any Oil In It Well? There The Only Ones To Service It .its There Fault Right ? Wrong They Said They Found A Tiny Pin Hole In It, Where The Pump Is Mounted And It Rubbed A Hole In It And Its Not Under Warranty Cause It Had 100.000 Miles On It
$ 2700.00 LATER here i am :help: ,has Anybody Had A Problem Like This ? ,and It Should Be Under Warranty ?

Well, after a good hot preassure wash this Sat. morning and a bit of UV dye. . .low and behold a pinhole just above the standing fluid level. A bit of Permatex epoxy and no more leaks!

Although my oil level went up about two inches in less than 1k miles. . .at least that's under warranty!

Well, after a good hot preassure wash this Sat. morning and a bit of UV dye. . .low and behold a pinhole just above the standing fluid level. A bit of Permatex epoxy and no more leaks!

Although my oil level went up about two inches in less than 1k miles. . .at least that's under warranty!
That is a temporary fix. Make sure you keep an eye on it. The damage is
already done inside and the pump will continue to wear bigger and more holes. The only fix is to remove the tcase and replace the rear half. I have a few cases here, I'll try to get a picture of the inside up later.

What causes it?

The only fix is to remove the tcase and replace the rear half.

Do you need to remove the whole tcase or is there enough room to slide the back half off wile in the truck? What other components do you relplace when this is done? Output seal. . .etc?

I figured I only bought myself some time, at least it's on the road for now. If something is rubbing wont the same thing happen over time to a new real half of the case?

listen to the Eric's on this one.. i had to replce the back half of the tcase on my buddy's truck. there is small piece of spring steel that acts as a vibration dampener for the pump. flimsy piece of steel breaks, pump vibrates, wears hold in case, fluid leaks... solution-replace back half of tcase. when you buy the back half it actually comes with the piece that breaks..

Are there any special tools or anything required? I assume it is a fairly straight forward job?

The transfer case needs to be pulled out and set on it's end to change the rear half. You will need external snapring pliers and standard hand tools, no special tools needed.

This picture is from the inside of the rear half. The pump splines over the output shaft and the ears of it rest in those notches.

Thank you for the great reply!! I will be doing this soon. Can you re use the gasket between the two halves of the case? How about the output seal?

i reused the output seal, and we used ultra black where the two halves meet. it isn't that hard as long as you have snapring pliers. i did my buddies in my driveway.. the snapring pliers go in teh hole with the oval shaped rubber plug in it..