Transfer case 101 needed
 

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.

Re: Transfer case 101 needed
 

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.


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

You’re welcome!

Re: Transfer case 101 needed
 

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.

Re: Transfer case 101 needed
 

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.