t-case has WAY too much fluid - from tranny?

[Daveo91Burb]

I've been having some small ATF leaks on the garage floor and have been chasing them out. Tonight I took the fill plug out of the t-case and at least a pint of fluid shot out of the hole. Nice and clean, too, just like the new fluid I recently put in my tranny. So is it the output of the tranny that's bad or the input of the t-case, or both? What parts should I order when I go to the parts counter? I know there's an adapter between the two - are there gaskets at the interface? This is a 4L80e / NP 241 combo in my 3/4 ton burb.

Will I lose much fluid from the tranny if I have to replace the output seal? Do I have to drain first?

Please help - if I don't get it fixed this weekend we'll have to take the minivan camping the next weekend, instead of the burb. Can't have that!

 

[bucket]

I don't recall for sure which seal is the culprit, I'm no trans expert. I think it's the t-case input seal. The adapter has an o-ring on the front and a gasket on the back.

If it just slowly transfers fluid over time, you can still drive it until it's fixed. Just drain the excess fluid every so often an add it back to the trans.

 

[flyboy1100]

One gasket iirc on the adapter.

I would think tcase input is bad. You will lose some from the tranny when you pull the tcase.

 

[Daveo91Burb]

Thanks guys. I found out seals are cheap so I bought both the tranny output and the t-case input today. But I may go with Bucket's suggestion for awhile and let it ride! (with monitoring, draining as necessary.)

 

[MadOgre]

Thanks guys. I found out seals are cheap so I bought both the tranny output and the t-case input today. But I may go with Bucket's suggestion for awhile and let it ride! (with monitoring, draining as necessary.)

Yes the 4wd 4L80 has a rear transmission output seal and a transfer case input seal. Looks like it might not be too bad to change out. As you can se there is a return port below the seal. Not sure how this all works between the transmission and transfer case. I believe the transmission output shaft is lubricated just like the slip yoke and thus needs a return port for ATF to be able to return to the pan while the seal separates the main body from the pan. I dunno. But one thing to check for is to see that the input gear on the transfer case is in good order and not cracked or wore allowing fluid through the gear and into your transfer case.


4wd 4L80 rear output seal

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