Automatic Transmission Sealant

J

JAKEFORD

Senior Member
The C6 in my 1971 F250 is leaking at the front seal when parked. When running it seems to be OK.

I was thinking of putting a can of that sealant in the transmission but the last time I did this my transmission acted up not shifting right.

Any comments?
 
I wouldn't. It has an additive that swells seals. That's fine except there is no control as to which seals and how much. The internal seals can swell to the point of them getting out of shape and then you have other larger problems. Unfortunately, the best way is to pull it and install a new seal. You can roll the dice with the sealant, maybe you will do well, maybe not.
 
I agree with the dude above. But, FYI, Lucas makes a very good product if you decide to try that.
 
More likely place for that leak is the intermediate servo shaft. There is a welsh plug installed from the factory but they tended to leak past them. As a matter of course, we would seal up the are around the plug when overhauling a C6. Lots of people have pulled the trans to replace the front pump gasket and seal only to find that did nothing to cure the drip. Front pump leakage seems to be more prevalent when parking the car/truck down hill and the fluid level is tipped forward and engulfs the seal. The shaft leak can occur any time the trans is parked on level ground. The fluid level will go up slightly and be just high enough to seep around the servo shaft. Of course if you park the car uphill all the time, things stay pretty dry no matter the weak point. Great transmissions the c6's are and they put beans on my plate for many many tears.
 
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