Technical TH 400 experts Help ..FIXED

So I just took my 49 Buick to town for the first time since I had the transmission rebuilt. 472 Cad motor and a stock 70 Cad th400 transmission. When I drove it out of my shop I had reverse. I drove it down the road and I am not sure if I had 3 gear. Washed the car and backed it up and drove to town. I may or may not have had 3 gear, it's hard to tell. Stopped at a friends place and when I went to leave I had no reverse. We pushed the car back and I drove it the 2 miles home, now it seems like I do not have 3rd gear, or reverse. This is a newly rebuilt transmission with 4 miles on it. I had reverse when I first tried it, the fluid level is correct. Any ideas what is wrong?

 

The direct clutch is applied in both high gear and reverse. If you do not have either I would suspect a problem with the direct clutch. The reason that reverse may have worked initially is that the direct clutch piston has 2 hydraulic reaction areas. The smaller of the 2 is used in high gear, while both are used in revers. There are 3 lip seals on the direct clutch and it is very easy to damage them during installation.

You can check for seal leakage with a pressure gauge. If it is a clutch seal problem, pressure will be low in reverse. If that is a problem, the transmission needs to come out.

 

I could be nuts, and most likely what jaracer said is the problem, but I think it could also be a check ball in the rear of the valve body. If they used rubber check balls one could have split and went through the plate. Shifter all aligned properly?

 

Shifter is correct.

 

I agree with jaracer, most likely an issue in the high reverse drum. Could be torn lip seals, broken sealant rings or something came apart.
The basic purpose of check balls in the valve body are to plug a larger hole in the seperator plate during the apply of an element and provide a rapid release of an element (band or clutch), wont cause no movement.

Bill

 

Found the problem. A snap ring came out of the 3rd/reverse drum, nothing got damaged and the trans is all back together. The guy that rebuilt it, drove over 100 miles one way, to my farm and removed the transmission, took it home and fixed it, and will bring it back and install it when we both have the time. I originally removed the transmission and brought it to him to rebuild. What a stand up guy, I am so lucky to have him do the job. Most guys would have said, bring it back to me and I will fix it, not come out and R&R it. He said the snap ring was his fault, no BS.

 

Stand up guy. For those in your area, maybe mention his contact info?

 

Now that is standing behind your work! Very rare these days. I agree , great guy.

 

If anyone in the Minneapolis/St Paul MN area needs a transmission rebuilt, PM me and I will give you his name and number. I am not going to post it here as I don't think he would like it. Brian