Transfer case 101 needed

[Bowed]

91 Silverado K2500 with 4l80e.




There are two 1 inch plugs on the rear of the transfer case . One at the base ( drain ) and one 5 inches above the lower one , which I assume would have to be the fill plug . When I removed the top one , about two quarts of fluid poured out . Even when it reached where the fluid was level with the base of the fill hole , it would not stop trickling out . I replaced the plug and started the truck up for a minute and I could hear that gears droning . I shut it down right away and yanked the transmission stick . The transmission was down 2 1/2 quarts . I refilled and restarted and everything seemed OK .

Question 1 - both the transmission case and transfer case should be separately sealed , so how would a cross leak like this happen ?


Question 2 - If I keep the transmission is kept at the right level , Can it be driven for the time being , with out causing any damage , even with the T-case over filled ?

Thanks.

[ChevyTech]

Question 1 - both the transmission case and transfer case should be separately sealed , so how would a cross leak like this happen ?

There is a seal on the front of the transfer case that has failed and is letting the transmission drain fluid into the transfer case.

I am amazed at how hard these seals get with both sides having fluid against the seal. I have seen them cracked and so hard they have no flexibility left at all.

Question 2 - If I keep the transmission is kept at the right level , Can it be driven for the time being , with out causing any damage , even with the T-case over filled ?

It depends on how fast the seal lets the transmission fluid into the transfer case.

Thanks.

You’re welcome!

[benoit454]

exactly the same problem I had. I drove mine for over a year or two that way, just had to constantly refill the trans, every 3 or 4 months it'd need a couple quarts. Then I never drained the t-case and it was overfilled of course.

it's not hard to change, and it's a cheap seal. I bought it at the local parts store think it was like $14 or so. Mine was rock hard, remove the t-case, you can either remove the 4(700r4) that holds the adapter to the trans, or remove the adapter from the t-case which is what I'd do. They are 6 I think bolts on my np241c case. I think they were 9/16 not sure maybe 14mm or so. Then take the t-case off and out, then there are 4 10mm holts that hold the ring on, the seal is in that ring. I flipped mine over drove the seal out, flipped it right side up and drove in the new seal, then reinstalled.

[Meatman]

When I has trans out of my truck for rebuild I put all new seals in transfer case. Mine was rock hard also and had a big split in it.