Cold TH350 not shifting into reverse

[doodah man]

Hi all,

I have a 72 with TH350 auto transmission and for the last week reverse doesn't work when I first start it up. It's been cold weather out. I can get it to go backward but only by revving the engine up and it barely goes.

All other gears work and it shifts normally going down the road. Reverse starts working after the engine temp starts to come up (usually after I've driven it about a block or so).

The fluid was a little low, so I added a pint. I haven't had a chance to check the fluid level again since adding ATF, but it's still not shifting into reverse at start up.

Any ideas what might be happening?

Thanks,
Craig.

[truckster]

I'm afraid it's not good news. If the fluid is full and it's still not going when cold, you're likely seeing the last legs of the transmission.

And don't change the fluid thinking that will help. With older TH transmissions, that will often be the last nail in the coffin. You flush out some of the friction material that's keeping it going, and it stops working at all.

[Bigdav160]

Yep, the rubber seals that operate the clutch pistons are getting hard.

[OLDROCK&ROLLER]

Been there and done that on some th350's. Change the filter and fluid.

Kenneth

[71 super]

As others have said on last legs, 1st will be next

[nicosorange]

I have heard that a bottle of Berrymans B-12 Chemtool will soften the seals and buy you a little more time...anyone try this?

[tomshortwide69]

I used trans x in mine helped a little bit

[doodah man]

I didn't specify in the original post, but you guys were supposed to give me good news!

OK, I'm gonna throw out a couple of other tidbits that I should have mentioned before.

I had the trans resealed about 2.5 years ago because it was leaking bad. I don't know if that included the seals on the clutch pistons or just what was required to stop the leak. The previous owner rebuilt the trans about 40,000 miles ago. Again, I don't know what that involved I just have an entry in his records that says 'rebuilt transmission'.

Also, the engine is running a little cold according to the temp gauge. Maybe the thermostat is stuck open a little. I was waiting for some warmer (above freezing) weather to do this. The transmission starts working normally well below the top temp so I guess this may have nothing to do with the other problem.

I will check the fluid level again this afternoon.

[doodah man]

Also we have one vote for "DON'T CHANGE THE FLUID & FILTER" and one vote for "DO CHANGE THE FLUID & FILTER". Anyone care to cast the tiebreaker?

[Bigdav160]

A "reseal" usually just is the external gasket to keep it from leaking fluid on the ground.

In a cheap rebuild, they just air check the piston seals and replace the leaking ones.

The reverse seals are buried in the bottom of the case and the hardest to replace. It might be they never got changed.

edit. I'm in the camp of changing the fluid never hurts. If the trans fails after a fluid change it was going to fail anyway.