Allison 5sp: fluid contamination?

[THEFERMANATOR]

I pulled the drivetrain out of my 01 donor today and noticed the trans was about 3 quarts overfull(the fluid had a very burnt appearance, but didn't smell burnt). So I drained the transfer case and found about a 1/2 quart in it, so I know where the extra oil came from now. I plan on freshening up the ALLISON now because of the motor oil from the transfer case having been in the tranny and it having been driven that way for awhile. Is there anything special I should do while it is apart because it was ran with the motor oil and ATF mix? My plans are for a SC3 and probably a 1050 or 1054 converter as my driving will be around town with 0 racing or pulling. I just want a tranny that won't die and I would prefer a lower stall converter for milage.

 

[Mike L.]

I pulled the drivetrain out of my 01 donor today and noticed the trans was about 3 quarts overfull(the fluid had a very burnt appearance, but didn't smell burnt). So I drained the transfer case and found about a 1/2 quart in it, so I know where the extra oil came from now. I plan on freshening up the ALLISON now because of the motor oil from the transfer case having been in the tranny and it having been driven that way for awhile. Is there anything special I should do while it is apart because it was ran with the motor oil and ATF mix? My plans are for a SC3 and probably a 1050 or 1054 converter as my driving will be around town with 0 racing or pulling. I just want a tranny that won't die and I would prefer a lower stall converter for milage.

I doubt the motor oil did any damage as I have run quite a few transmissions with motor oil.

 

[R-Fast]

tranny oil contamination

How does the TC oil get into the tranny? Will this condition occur on an 04 LLy automatic?

 

[Mike L.]

How does the TC oil get into the tranny? Will this condition occur on an 04 LLy automatic?

The TC is sealed but the Alli isn't. If the front seal on the TC goes bad it will leak into the Alli.

 

[THEFERMANATOR]

The TC is sealed but the Alli isn't. If the front seal on the TC goes bad it will leak into the Alli.

That's what happened to this one. The transfer case seal is nice and cracked in it and it ran into the tranny. I'm used to 4L60E's with 241's where the transfer case overfills with oil normally and you lose tranny fluid with no visible leaks. It's always nice when you pull the drain plug on the transfer case and get 2 gallons come running out in a BIG hurry.

 

[R-Fast]

fluid contamination

Another stupid question, Is there not more fluid pressure in the transmission than the TC, and if so when would the transfer of fluids occur?

 

[Mike L.]

Another stupid question, Is there not more fluid pressure in the transmission than the TC, and if so when would the transfer of fluids occur?

There is no pressure at the tail end of the trans; only residue from lubrication to the geartrain. The TC on the other hand has a pump that is spraying gears for lubrication and the seal is to keep spray within the TC. When that seal goes bad, the TC fluid leaks into trans.