Transmission Fluid in Transfer Case

12-20-2005, 02:00 AM
I recently noticed transmission fluid getting into the vacuum system on my 1995 Jimmy SLT 4.3L. I read one of the other posts here where someone suggested replacing the vacuum switch on the transfer case when they experienced a similar problem which included transmission fluid building up in their transfer case. I pulled the drain plug on my transfer case and drained about 7 QUARTS !!!! of fluid from it...WOW! I changed the vacuum switch and refilled the transfer case with about 2.3 pints of new fluid until it just started to come out of the fill plug hole. I've haven't even driven it 1000 miles and checked my transmission fluid today and noticed it was low....roughly 2 quarts. I put a drain pan under the transfer case and removed the fill plug and drained off roughly 2 quarts of excess fluid. Does anyone have any suggestions about how the transmission fluid is getting from my transmission to the transfer case ? I know there are seals between each of them but could they both be bad at the same time ? It seems like I may notice a slight leak between the transfer case and the transmission if the seals were bad. I'd appreciate any suggestions and thank you for your time.
Tucson, Arizona

12-20-2005, 07:00 AM
This is a fairly normal occourance. The seal between your transmission and transfer case is shot. There is no real harm unless your 4x4 starts working. You can let it go to that point without damage. If it's irritating you enough, it's not a difficult repair...3 dollar gasket.

01-23-2006, 11:59 AM
This may be a fairly common problem but it has a lot of consequences. My 96 Jimmy had transmission fluid in the majority of the vacuum system leading to leakage inside the cabin at the heater and AC controls. If you don't fix it, real problems can develop. It also causes transmission fluid to come out of the breather tube (has a little filter at the top). I suggest you fix it ASAP. After I replaced the seal between the transmission and the tranfer case in mine, I had no more problems. Also, you don't keep losing transmission fluid.

01-28-2006, 06:49 PM
Thanks for the information "acharles",
I've unfortunatly had all of these problems develop after having the excess fluid build up in the transfer case. The fluid started to come out of the breather(near the passenger's side exhaust manifold), the AC switch was ruined and I suspect the problem I'm having with one of the duct actuators is also the result of the fluid getting into the vacuum system.
How much did it cost you to have the seal changed or did you change it yourself ?
I suggest any person experiencing these problems gets the seal fixed ASAP to avoid all these problems......
Thanks again

01-30-2006, 08:07 AM
I forgot to mention in the last post that transmission fluid also got into the vacuum ball mounted under the hood and the 4 wheel drive actuator under the battery holder. There may still be a small amount of fluid in my heater vent control actuators. It was a real mess! I don't know why GM designed their 4 wheel drive system this way with the problems it can cause. You may want to vacuum your vacuum hoses and system, if possible. Anyway, I changed the seal myself. It's not a tough job if you have a service manual or guide book. Make sure you buy a genuine GM seal as it is made much better than the one's from NAPA or the other parts stores. Basically, you remove the two drive shafts and the transfer case. The seal is in the back of the transmission, which does not have to be moved. I used a seal puller to remove the old one. My Jimmy now has 160,000 miles on it and is running strong. Hope this helps!

01-30-2006, 09:43 AM
I had transmission fluid in the vacuum ball too. Man, it was hard getting it out of that thing !!!!(I found running hot water over the outside of the ball expanded the air inside of it and helped to purge the fluid out of it)....I also replaced most of vacuum lines in the engine compartment. I plan on replacing the seal ASAP....till then I just am monitoring the fluid being lost to the transfer case and doing a "routine drain off" of the excess fluid. I really appreciate all the advice you've given. I do agree it is a poor design of the vacuum system if this is such a common problem.
Thanks again,
Tucson, AZ

02-16-2006, 12:07 AM
Hello again "acharles",
I wondered if you knew the dealer part number for the seal you replaced in the back of your transmission. The dealer here in Tucson was not sure of the seal I needed.
Thanks again for your time,
Tucson, AZ

04-21-2006, 11:07 AM
I have quite a number of seemingly related problems and after reading these posts, I think you've helped diagnose my root cause with the bad tranny/xfer case seal. I've got tranny fluid in all the vacuum lines (drilled a little hole in that vacuum ball to clean it out then used hot glue to reseal it) (update 09-Jun-2006: The engine bay gets hot enough that the glue softened and got sucked into the ball...use something else!), A/C not working right, 4x4 hard/impossible to engage, tranny fluid disappearing.
I was thinking vacuum leak but if that were the case, the hoses would be leaking tranny fluid at the break. Guess I'll be spending a rainy weekend under the truck! Thanks everyone!

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