904 1st and 2nd want to be reverse

[Jeff360]

904 behind a 408. 99% strip car. The transmission has four weekends on it. This Sunday after a pass car would not go into 1st or 2nd. It would go into 3rd and I hobbled back to pits. It was fine after a few minutes and I kinda forgot about it. After the next pass, one of my best 60’s. It drove fine.
20 minutes later car would not go into 1st and 2nd. It kinda felt like it wanted to move but would not. Added 1/2 quart fluid. No different.
Later it was fine and ran again. No issues.
Car sat for 45 minutes and when called again for race, car would not go into 1st and 2nd again, now when shifting into 1st and 2nd and neutral, all are reverse gear, 3rd is fine. Checked the shifter/valve body sequence, it’s good.
Temperature at sensor in pan is around 150F.

I load car into trailer.
Monday, offloading the car, all is fine. Does nice burnout in driveway.
I’ve drained the pan, fluid looks good, (in a different time I’d consider reusing it), I dropped the pan, nothing terrible, filter looks good, no burn smell.

I bought the transmission a number of years ago and know only that it was a hodgepodge of 904/998/999.
It’s a non lock up, low first gear, one four clutch drum, one three clutch. 4000 stall converter, CRT reverse manual valve body with Cope’s recommended servo and 4.2 lever. Transmission was rebuilt last year buy a good transmission guy who mostly does turbo 400’s. He’s also, at the time, wanted it to have a billet drum with five clutches.
Transmission guy suggested that reverse and 1/2 have fused together.

Any ideas before a pull it out?

 

[Desoto291hemi]

No debris in the pan

I would check valve body first
Especially being it is not working and then working again
Sounds like something is sticking

 

[Oldmanmopar]

Get another valve body and try it. Sound like its in the valve body issue.

Just posted this in another thread . This demons bad valve body killed this 17 year old. Shifted from 2nd to 3rd full throttle and the trans locked up. It was the valve body

 

[71Demon540]

Many of possibilities for this issue. Could be a valve body cross leak. Could be many other things.

Check to make sure the low/reverse servo did not come out of the servo bore, which would apply the low/reverse band virtually all the time. It should have a billet solid low/reverse piston kit with the RMVB. It sounds like the front clutch is being applied constantly. Which would explain why it has 3rd gear but in neutral, 1st, and 2nd it wants to go into reverse. Not sure why it is intermittent like it is, which points to the valve body cross leak potential. If you have another valve body I would swap it and see if that fixes the issue. And if you drop the pan, and see the low/reverse servo hanging out of the bore, that will need addressed before trying another valve body.

I hope this helps.

RJ

 

[Jeff360]

Update.
I pulled off the valve body. Disassembled it completely, all pistons and balls, cleaned everything and reassembled.
Adjusted the bands, I could almost get my finger under them. Air checked all the ports, all good.
Reassembled the transmission.
Back at the track this past weekend, all good. It does in fact have a little bit more go in the 60. Not an improvement on slip, but something I felt in the six passes I got (test and tune plus competition) before elimination.

 

[71Demon540]

Update.
I pulled off the valve body. Disassembled it completely, all pistons and balls, cleaned everything and reassembled.
Adjusted the bands, I could almost get my finger under them. Air checked all the ports, all good.
Reassembled the transmission.
Back at the track this past weekend, all good. It does in fact have a little bit more go in the 60. Not an improvement on slip, but something I felt in the six passes I got (test and tune plus competition) before elimination.

Happy to hear you got it straightened out. Nothing is better than just a simple clean and reassemble.