493 wedge, 64 Dodge NSS car, 9.90-10.10 ET, 727 with aluminum front drum, 5 pinion steel planetary, LBA valve body, 16 element sprag, rear roller support. I rebuilt this trans around 2012, we cleaned the splines out of the aluminum planetary in 2015, so I replaced it with a 5-pinion steel planetary. Trans has been flawless tha last 8 years until last weekend. We do change the fluid every couple of years and the level was OK. Trans developed a flare on the 2-3 shift that got worse with each run, but would eventually shift. Didn't hurt ET much as we made it to the final at Cecil. It flared in the final on the shift and when he pedaled it in the lights as the engine flared again (about 600 rpm over normal). First and second gears are OK. Shifts ok at part throttle on return road. Gonna pull it in a week, but since I haven't seen this type of failure (we've broken just about everything else in the trans before), just want to get an opinion on what I may find when I pull it apart so I can be sure I have the parts on hand or order ahead of time.

Two things I would look at, the front band and the high gear clutches
I would see how far out the front band adjusters is out now then count the amount of full turns it takes to get it to have 72inch lbs. torque to snug it up against the front drum, if it takes 6 or more turns look closely at the front drum and band
If it takes less than 5 full turns to snug it to 72 inch Lbs. then take the tranny out and look at the front clutches
In the future I wouldn't run it anymore after the first flare on the gear change, either correct it at the track if it is the front drum or take it home and fix it if it isn't the front band

Agree with Cab, from previous experience. How does the fluid smell ?

Fluid smells fine. I'lll check the front band first. In previous rebuilds, the clutches show no wear.

The band applies in 2nd gear only. The front clutch applies 3rd gear. There will be your problem. Either the front piston seals are leaking or the stator support rings are an issue. The support rings seal the forward drum to the input shaft. This is the oil feed path to the front clutch piston. Pay close attention to the rings. If they are worn on the sides the grooves in the stator support will be worn. Replace the support or it will happen again. The clutch fibers and steels will be damaged as well.
Doug

Thanks, will take a close look at that.

My two experiences with this failure mode have been lack of a deep pan that resulted in lack of fluid in high gear only, and just last year or so, lack of valve body pressure....The later I had it turned up to the proper amount. It was CRT that found this issue. We weren't sure why as it was the second time my 605 lightly burnt the clutches. I already have the 5 gear setup, just not the complication of an aluminum billet drum, mine is steel...I do not know what the proper pressure is or how he checks it, but runs good now....