My dads '79 Ford 4x4 acts like it slips just as it shifts. It has a 351M with a C6. Just as it shifts, the RPM's jump up, but theres no slippage while going through the gears, only as it shifts. Is there an adjustment that can be made on these tranny's to cure this problem?:confused:

You could put a shift kit in it,they were designed to slip a little for a smoother shift,it will firm up the shift and help it run cooler too:D

Sounds like it is almost time for a rebuild, the slip between gears is normaly caused by the servo getting gumed up. You can get quite a bit more lige out of it if you remove the 4 bolts holding the servo cover on and clean it out, also check to see if the servo has any cuts, or hard, rubber.

Then after that you can try to adjust the band, then clean the valvebody, then rip it out and rebuild it w/the shift improver kit.

I'll look into that servo deal. Also, how would I go about adj. the bands?

I can't remember right off the top of my head, but I think you tighten the adjuster to like 10 foot lbs then back it off 3 1/2 turns. Not quite sure but you can look it up in any manual.

Originally posted by emsoffroad
I can't remember right off the top of my head, but I think you tighten the adjuster to like 10 foot lbs then back it off 3 1/2 turns. Not quite sure but you can look it up in any manual.

Thats what my tranny manual says, I had the same issue, my fix was to tear the valve body apart and clean all the dirt out, and then put a tci shift kit in it.

Thanks for the info! It's probably one of those "all of the above" type problems. This truck sat for nearly 10 years before my dad bought it. The valve body's probably gummed up with mung!

I would stay away from the TCI kit. It works good but you can get a better setup for less. Get the one that the tranny shops put in every tranny and installl to your liking. I think the last one cost me $10-$15. The nice thing about the TCI kit is you can get it at almost any shop/store.