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Front transfer case input seal

12-09-2006, 11:36 AM
IS there such a thing?

Just got back from the dealer. I asked him to diagnose why my s10's transmission was drinking fluid. (Problem previously posted. Concensus was leaky rear transmission seal)

Whats written on the ticket: Diagnosed to front transfer case input seal leaking allowing transmission fluid to escape transmission and enter transfer case and sucked into engine and burned via transfercase vaccuum switch.

MY BS radar is pegged because he originally said rear transmission seal leak. and it wasnt until I inquired why it wouldnt be covered under the transmission warrenty that he said "Did I say rear transmission seal, I meant front transfer case seal" (its a rebuilt tranny with 2 yrs left on a 3 yr warrenty).

I also repalced the vaccuum switch 2 months ago. I being BS'ed?

Another question: can a new vaccuum switch still suck fluid?

12-09-2006, 02:23 PM
It is my understanding that the transfer case front input seal is a double lip seal that keeps the two fluids separate. There is no rear transmission seal.

On mine the transmission fluid went into the transfer case causing it to be two quarts over full. It only did this during the hot summer and I am thinking the transmission may have been overfilled (my wife, not me) or the vent tube to the transmission was plugged causing excess pressure.

Since it has cooled off I have not had a problem. I keep an eye on the transmission and check the transfer case regularly.

If it is getting sucked into the motor via the vacuum hose then you have another problem.

I have bought the new seal just haven't had time to take it apart.


12-10-2006, 11:03 AM
Mine sucked up that fluid into vacuum lines and ball yrs ago. Had to drain lines all the way up to dash air controlller behind climate control panel. Vac ball needed blowing out to. Found out becasue air controls stopped working so I started checking all vac lines for cracks or whatever.

This all started after I noticed the 2 vac lines to transfer case switch on top were off. I think maybe I hooked them back up wrong.

I had shop change the vac switch. They must have hooked them up right. There is a 3rd line which is vent. So if suction line put on that, well, maybe your shop did this and simply wonh't admint it ?

I've had none of those probs since switch change and correct line hookup there.

12-10-2006, 11:20 AM
Mine has been doing it for over 5 years. I think it's time to drain the transfer case, lol.

12-10-2006, 12:40 PM
There was a problem with the vacuum switch from the factory on the 2001 and later S10's. The original part # 15664811 was defective, it has a green inspection mark on it. This was replaced with part # 89059420 with a blue inspection mark.

You can read more about it here, the link to doesn't work but if you keep reading, you will find all the info you need with pic's.


12-10-2006, 02:23 PM
The transfer case was removed for the transmission job so yes they have to cover something they did - doesn't matter if on transfer or transmission they pulled them but out and apart. If its 4 button autotrac this is a major problem becase the transfer case requires blue GM syn fluid not red Dexron as the trans does. 3 button all red but it has a 3 port vac switch that when 2wd selected connects the transfer vent to the front actuator line to release the front actuator so if fluid is building up it can get in there.

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