no gear when warmed up

[gotlag]

OK. Not normaly one to go looking for help, but I am stumped, and don't want to hurt anything.
Couple weeks back, my tranny finally gave up. Had 156K on it and I run the track every weekend and I run it hard (mid 7's in the 1/8), so I was waiting for it to go.
When it did go, it would move when cold, but after a couple hundred feet it would drop out of gear, and you would have to wait for it to be cold before you could move the car again.

Not being new to building auto trannys, I had no qualms about dropping this one and going through it. When I was in the trans, the low/brake pack was burned BAD, and of course so was the end cluthes. I went through the entire transmission, all new steels,clutches,sealss,etc, and went back through the valve body as I had previously installed the kit from IPT. Started it up last night to be sure it would go into gear and it did so I drove it off the ramps and tried foward and reverse in the driveway, and all felt good.
Came home today to tidy everything up, fired up the car, put it in gear and turned the car around just fine. I left it running as I reprogramed the DSMlimk, then was ready to go for a test drive, put it into gear and it dropped rpms a litlle but would not go foward, just reved. Same with reverse.
Let the car cool down for 30 minutes, fired it up and car went right into D and R no problems. Moved the car, let it idle, as soon as it got to operating temps, then the car again loses the ability to go into gear. Wait 30 mins and car is fine again.

Any ideas at all??? No codes, solonoids clicking away, cable adjusted, an as I said, a bit stumped and don't want to hurt a fresh rebuild.

 

[gotlag]

Little update...was about to start pressure test and decided to pull the cooler line for giggles, put it in low and noticed very little flow. Could stop it with my finger. Had an odd pulse to it. So figured time to drop pan for quick check. All looked good so I dropped the filter. Fluid came pouring out of the tranny of course.Well I tried pouring fluid through the filter and it would not flow through. Thought that was odd as it was new from the master kit. So I grabbed another new filter from the bench, installed it, put the pan back on dropped 5 qts ATF in, started car and now it has fast and solid engagement in foward and reverse gears. Feels great. Started to rain, so I have to wait to drive it and see how all the gears react, and shift points and feel. I have let it run for 30 minutes and even hot I still have gear engagment.