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Old 11-16-2015, 01:12 AM   #1
Registered User
Join Date: Mar 2013
Location: Sacramento CA
Posts: 105
89 Suburban - leaking TH400 transmission

So my TH400 is dumping fluid. I "fixed" it once. It lasted a few days. Now dumping fluid again. 1989 burb with the 6.2 diesel.

I dropped the pan, checked it carefully, put a nice thick gasket on there, sealed it with Permatex gasket sealer. Torqued to specs (144 inch pounds). The problem is not the pan gasket.

The problem (well, at least one known problem)is the kickdown switch/solenoid, located on the driver side of the trans just above the pan gasket. It was loose and wobbly because it's O-ring was worn and flat. I tried to fix it by getting a set of O-rings from Autozone. "HELP!" brand. I got 2 O-rings to fit where the old, flat one had been. I had a hell of a time getting the switch stuck back into the trans case, but I did it, made it click into place. It was very snug with the 2 new O-rings.

Now, after driving it a bit, the switch is loose in the socket (side of the transmission case) again, and is dumping fluid. I think the hot transmission fluid somehow got the thing to loosen up. Just a guess.

So, what now? I can drop the pan again (we all know how much fun that is), get this stupid kickdown switch loose, and do what to it to make it stop leaking? Slather black RTV on it?

Also: the kickdown switch does not work. It possibly was never designed/intended to work with the 6.2 diesel.

If I am fine with it not working (which I am), why not just leave the kickdown switch out of the transmission case hole and put some sort of a rubber stopper in the hole instead?

All advice or comments are appreciated.
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