Transmission slipping

[ksurfer2]

I have a 727 that was rebuilt about 2 years ago by Champion Racing Transmissions in Sarasota, FL. There is a PTC converter that is about 3 years old. There have not been a lot of passes on this set up. Maybe a total of 50 over the past three years. Over the past couple of outings to the track, the transmission will "slip" at the hit. This will knock about .10 off my 60' times. It will only happen the first hit of the day, the rest of the time it will be fine. The fluid is fully topped off and shows no signs of discoloration. I do take a drive around the pits to get everything warmed up before heading to staging. Any idea what could be causing this?

 

[493 Mike]

Does your VB engage the rear drum in low gear?
Mike

 

[dvw]

Do you really think it slips? Or does it shudder? If it has a low band apply valve body it shouldn't ever slip. It would take multiple imternal parts failures. If it doesn't have low band apply, the low roller clutch (sprag) would have to be damaged. They usually shudder or fail completely very quickly. How does it feel driving around in the pits? Higher than normal rpm to move? If thats the case it could be a damaged stator sprag in the converter. My sons car we swore it had a damaged converter. Even felt like it was slipping in the pits. Upon teardown PTC said the converter was fine. Trans clutches and bands looked good as well. Swapped converters, same issue. On the 2nd inspection he found a crack in the valve body at the converter valve. The reason it slipped wasn't the trans clutches or bands not holding. It was the converter not being fully filled with fluid. Kind of like when you have a Torqueflite thats been setting for a period of time. You go to take off the first time and it feels like it slips. It's tame thing. The converter has drained back and hasn't completey filled.
Doug

 

[Armyvet25]

your avatar looks like the face you'd make when it happens

 

[Dave6T4]

I just started pulling down a friend's Push Button 727. So far, wrong 1-hole filter and broken Belleville spring. Betcha it was slipping, too.