Leak between transmission and transfer case

[075.9Cummins]

I’m leaking ATF thru what looks like a weep hole between the 48RE and NV273D. What’s the likely cause?


The weeping seems continuous with the truck at a slight incline in the driveway. I assume there is at least one seal on either the transmission output or the t-case input… or maybe one on each? Since the rebuilt transmission has 90,000 miles, I’d guess the problem would be a seal on the t-case but can’t find anything clearly addressing this issue.


With 365,000 miles I’ve rarely, rarely used the 4WD but it’s still a lot of spinning thru the t-case. Probably 500 miles on snow covered roads and a couple hundred miles on not so bad dirt roads. Earlier this year about ~75 miles total in low range creeping down steep trails in Utah and Nevada with a heavy truck camper. I’ve never had any issues with the t-case. Should I expect a rebuild at this time or just a seal, or two, or three?

Attached pic shows location of weep looking forward from under the rear of the transfer case.

What do the crystal balls show?

 

[Darkbloodmon]

There is a seal on the transfer case input. On my NV5600 output there is a recessed oil seal that the input shaft on the transferase slides into on the splines and gets lubed by the transmission fluid.

370K is a good bit for a transfer case, that's a run time most modern cars don't see. I'm not one to wait for issues to happen but use your best judgement before talking to your accountant. The seals are simple enough to replace.

Since both the trans and T case use the same fluid I wouldn't knock the output on the trans being the culprit until you can confirm. Checking over work is even more important nowadays, the assumption of someone elses attention to detail can and will bite you in the rear.

 

[DonFitzwater]

The weep hole is an odd topic. Years ago I decided to apply sealant to the mating surfaces, not to keep oil from leaking out but to keep road contaminants from getting in and affecting the seals and the sealing surface of the shaft. There are actually 2 seals in there, one on the rear of the trans and the tcase shaft slides into it and the other seals the input shaft on the tcase side. It's rarely the tcase seal that leaks. I'd pull the tcase and replace both seals, apply a bead of high quality RTV and reinstall the tcase.

 

[bcbender]

My NV5600 leaked MTF from that hole after I was hit in the side by a texting beach Barbie..(totaled her car... I only needed a replacement front axle, wheel and fender... I drove it home. ) I never fixed the leak, but as has been said, if its leaking likely the TM or TC seal is the culprit, one should be loosing fluid. FWIW, be cautious about too much RTV on the flange, I had a co-worker RTV his 94 F-150 t-case to the auto trans and when we needed to pull it to replace the trans fluid pump, it would not come off the transmission no matter how hard we pried. might use a thin layer or some anaerobic sealant.

DB.. I have two of those seals for the NV5600 on my shelf as I was gonna fix it but never did so if you or anyone else ever needs one. just pay shipping

 

[Darkbloodmon]

anaerobic sealant

Totally forgot to mention Loctite 545. It's a liquid sealant. I use it on every seal or O-ring possible, really great stuff.

DB.. I have two of those seals for the NV5600 on my shelf as I was gonna fix it but never did so if you or anyone else ever needs one. just pay shipping

Noted!

 

[075.9Cummins]

Thanks for the responses!