Problems after rebuild of 350 Transmission
 

My problems began early this year when I made a pass down the dragstrip and the front u-joint failed @ about 100 mph. Fortunatley I had a driveshaft safety loop on my car and that saved me and the car from even more damage.

The remaining portion of the driveshaft smacked the tailshaft so hard that it cracked the tailshaft and it did not stop there. The transmission case was cracked all the way to the bellhousing and I basically had to replace a bunch of parts including the transmission.

A new case was found and most of my parts were taken out of my old transmission and transferred into the new case. We salvaged the valve body and shift kit and installed hardened sprag races and blue plate clutches.

Here is the problem:

I had the car for 2 days (drove it for about 10 miles) and noticed that when I played around with the shifter (by putting it in low gear) the transmission behaved strangely. It looks like the vehicle wants to come to a stop. I could not figure out how to reproduce the problem. When I tried to reproduce the problem I lost 1st gear completely. I could rev the engine up to 3000 to 4000 rpm and the vehicle would not move. It would only move in Drive or Reverse.

I brought the vehicle back to the shop last week and went to pick it up today after they had fixed the problem.

The transmission is still not working propberly and is behaving as if there is a force that wants to make the car move forward and another opposing force that wants to bring the car to a stop. This problem occurs in 1st gear and not in drive.

The shop now says that they believe that the valve body is the culprit but I'm not sure that I believe this. I guess it's possible that my old valve body was damaged when I grenaded the transmission - but how likely is that?

I have searched the archives but have not found anyone who has reported the same problems.

I'd appreciate hearing from anyone who has ever run into this problem or knows what is wrong.

Thanks in advance.

Sounds like the valve body. I havent seen a hydraulic schematic for a TH350 in a while, but it sounds like its sending fluid somewhere that its not supposed to go. I'll look it up and see if I can "guess" as to where the problem may be. In the mean time, dont shift it into low-1!

OK... Here goes...

To make things simple, when you put the tranny in low 1, the valve body is sending fluid to the forward, low reverse, AND DIRECT CLUTCH! Its not supposed to send fluid to the direct clutch! You basically have a trans brake! Not good!

The valve body could be damaged. If it has a crack in it, it can bleed apply pressure over to the DIRECT CLUTCH port and engage it. Or the low/reverse clutch center seal may be missing or cut. That can bleed fluid over to the DIRECT CLUTCH also.

Take it to the shop and have them go through the tranny AGAIN. If they built it for you and you havent had it back for a week, then they should honor a FULL REBUILD. Especially if someone did a poor assembly of your transmission.

Damn I hate automatics!!!

Thanks for the information that's exactly how my transmission is behaving - like a trans brake.

Do you think the valve body could have been damaged when the transmission got whacked by the out-of-control driveshaft?

Or do you think it's most likely due to the "low/reverse clutch center seal may be missing or cut."?

Since they used my old valve body when they assembled my transmission, I'm sure that they will try to bill me for the valve body even if the problem was with the center seal.

Thanks for taking the time to reply!

I forgot to ask you about the purpose and function of the direct clutch.

When should there be fluid going to the direct clutch?

The DIRECT CLUTCH is only used in reverse and drive range 2nd (not low 2!). The purpose of the DIRECT clutch is to drive or hold the sun gear (depending on what range the tranny is in). It drives the sun gear in reverse and holds it in drive range 2nd.

Hope this helps...




[This message has been edited by JAYDUBB (edited April 19, 2001).]

It could be either or. You really wont know until they pull it apart.

I got my transmission back from the shop and they said they had to replace the valve body - like you said. Thanks for your help!

Not a problem. Always glad to help!

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