No reverse trouble
 

Hi there,

My 1970 c20 didn't engage reverse after sitting a while. The rest of geras go fine, but nothing happens when i put in on revese. Anything I could do before opening the whole thing up?
In my country automatic transmissions are sci-fi. Three mechanics told me already they won't try.

Any help will be appreciated
Thanks

Re: No reverse trouble
 

The first thing I would do is check the transmission fluid. If I remember correctly when the transmission is cold the fluid should just barley show on the bottom of the dip stick.

LockDoc

Re: No reverse trouble
 

Thanks, I'll start there.

Re: No reverse trouble
 

Does it go into Park OK? If not, the linkage adjustment may have slipped. Let us know what you find.

LockDoc

Re: No reverse trouble
 

I rebuilt a TH350 for my kids Jimmy this summer. I had a little help, but this is something you can do if you have to. TH350/TH400 similar but different so just get the appropriate manual. Or two. Or three. Read online, some good threads.

And read online. Buy a comprehensive rebuild kit. You will need a few special tools, but they can be had or made for less than $100.

Get a big, clean work bench so you can disassemble and leave parts in sub component groups.

Clean and replace all parts measuring where needed and reassemble.

Re: No reverse trouble
 

Try adjusting cable underneath cab on transmission

Re: No reverse trouble
 

Run the engine until it is fully warmed up.

With the engine running, put the selector in each position, then put back in park.

On a level surface, when you pull the stick, clean it off, and then test the level. The fluid should be at the top of the hatched area.

I was down a little on my stick, and the reverse shift was sluggish, until I filled it to the top of the indicator.

Re: No reverse trouble
 

Thanks guys, when you're up we're sleeping over here, so it's nice to get up and find all this help posted.

I'll check all these things today and let you know. All gears go in fine, even reverse, but it won't move backwards.

I'll check levels and cable this afternoon and will get back to you.

I don't know if I'd be able to open it up, but willing to try. I wanted to check all options before.

Thanks a lot for your posts, they really help.

Re: No reverse trouble
 

Fluid and cable are fine. I hear a rubbing metal noise when I put it into reverse, like a gear trying to engage but not doing the job. The rest they all engage fine.

Re: No reverse trouble
 

It is possible the park pawl is still partly engaged and that is what your hearing. Dropping the pan would reveal if that is the issue. I have seen them broken off in the bottom of the pan. Link to show the parts involved.

http://www.atiracing.com/links/pr/20...arts/index.htm

I would also recommend reposting your problem in the link below. Lots of expertise there.

http://67-72chevytrucks.com/vboard/s...d.php?t=668062

Re: No reverse trouble
 

Great HO, I'll check that and repost, thanks.