I have a 85 Pontiac that originally had a 200C transmission but just got through putting in a TH350..It shifts great even though I have not hooked up the kick-down cable yet.I have two leaks that I need to ask some questions about.
My bad leak is at the dipstick tube.This tube has a o ring near the end of it but the tube does not have a bracket so as to mount it to keep it from flopping around.The 200C had a bracket pressed on the tube that bolted to the bellhousing to engine bolts.
Are the holes for the th350 and th200c the same?The reason for asking is that I was thinking about using the dipstick and tube that came out of the 200C trans even though they have a different contour,The tube out of the 200C has a different type of seal,It fits inside the hole and then the dipstick fits into it.
The other leak is where the speedo cable goes into the trans.I am assuming that there is a seal or two that goes there also?How are they installed?Part numbers?
Any info or past experiences with soloutions with these problems would be greatly appreciated.
Thanks,Allen

The dip-stick tube has a thick O ring to seal it, just about all the TH-350's i've seen had a tab to bolt the tube to the back of the cylinder head.
You could fab up a L bracket, and worst case use a hose-clamp to secure it. The speedo cable leak is pretty common, there's a regular O ring
around the gear retainer that you can replace. Disconnect the speedo cable, take the 7/16" bolt out of the retainer clip and wiggle the round retainer out. The driven speedo gear will come out with it, replace the O ring around the retainer and re-assemble. If your interested, Lokar makes a really nice trans dipstick / tube in braided stainless. I got one when i stuffed a 350/TH-350 in a '89 S10 Blazer, worked like a champ.
Don