Automatic transmission

monkeyman29 · April 20, 2004

I just bought a 1981 GMC C10 PickUp with the 305 and the 2 barrel carb in it. It runs not too shabby after I adjusted the choke a little ... However It has a hard time shifting gears. The Transmission fluid looks a little burnt and if I really punch it it changes gears..... Is it the cable from the carb to the tranny, that might be loose, it looks a little frayed and sloppy on the carb end? Maybe better off just swapping transmission.... Any suggestions would be appreciated.

Thanks.

Colorado Kid · April 21, 2004

Your trans is a TH700-R4.

You are correct that the cable (Called TV cable or Throttle Valve cable) adjustment is causing the symptoms you're observing. Unfortunately the missadjusted TV cable has probably destroyed your clutches. A GOOD tranny shop can make a pretty stout unit out of a burned up 700R4, but some internal attention is going to be necessary.

Not good news, but it sounds as if it's what you expected.

BuiltNotBought · May 25, 2004

If your fluid smells alittle burnt it's probably a good idea to go ahead and do a filter and fluid change on it also.

rayciesboy · June 6, 2004

I may be wrong, but I don't think the 700R4 was available in 1981 C10's.

More than likely, with a 305 and a 2 barrel carb. in a C 10, you have a Turbo Hydromatic 350 trans.. These were widely used in light duty trucks for many years.

Look at the trans. pan. If it is square, it is a TH 400. If it looks like it has a corner cut off, it is a TH 350.

When you rev the engine, the pump is creating enough extra pressure to make the trans. shift. If the fluid smells burnt, it is too late for a fluid and filter change, it's time for a rebuild. I was looking on eBay the other day, and there are all kinds of TH 350's for sale. Anything from stump pulling performance trannys to used and abused. Just depends on how much money you want to spend. Or, you may be able to find a local trans. shop to rebuild it for you. You can probably plan on spending about $800.00, depending on whether you have any performance parts installed.

The cable you are talking about is probably the kickdown cable. It drops the trans. down a gear when you stomp the gas so you can pass. Good luck.

snoman · June 6, 2004

It should be a THM350c with a locking converter. If fuild smells burnt, flush it out anf change filter too and you might add a aux tranny cooler if you plan to horse it a bit too.