Transfer case keeps filling with fluid, tranny goes low

big al

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#1
Make
Chev
Model
Silverado
Year
1998
Miles
156000
Engine
5.0
This is a familiar truck and i know its history. 98 Chev Silverado 4x4, 4L60,5.0 v8, 156,000 miles. Transmission was rebuilt by a reputable shop NOT by me, about a week or 2 later truck comes in for leaking transfer case. Yup front shaft seal pouring fluid out, drained case to do seal job, refill properly to level. About a week later truck back for leaky transfer case again, also says newly rebuilt transmission not (shifting or acting right). Ill take a look. Trans is low transfer case is over fill plug. So i think Hmmmmm, drain case to just below filler plug , fill trans. He says great trans is back to normal and no leaking. 2 weeks later back again same issues with same remedies. My ? is this, does this 98 4L60 have the rear seal that can fail and push trans fluid into the transfer case??? He has a warranty on the trans but must travel a distance to have it serviced. I know this truck well and this transfer case NEVER had an issue and has maintained well in the past
 

big al

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#2
The front shaft seal has not leaked since i replaced it.
 
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#3
I think you know the issue BUT for a second opinion I will say likely a trans issue.

Trans level goes down Tcase goes up. Correct?
trans seal, trans vent, or gremlin with a sense of humor, and extra time.
 

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big al

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#4
Yep, trans level goes down, transfer case level goes up, thats correct. I was thinking i was correct but yes i wanted a second opinion before giving him the news i thought is correct. When levels are where they are supposed to be this truck operates great. I would rather have him take it back under warranty.
 
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#5
If this was an old Jeep, I would say that rear seal in transmission is leaking or installed backwards, and there is no working weep hole between the two units. ATF can leak into the transfer case because the transfer case front seal will let it in. Or if the two units share a vent system, foamy transmission fluid may make it's way into the transfer case.