727 build fail

Rebuilt my 727 and now it seems to be binding in two gears occasionally. Mostly stock build with the exception of a TF 2 kit in valve body. I have build a dozen 727's and never encountered an issue like this.
Its felt kinda sluggish like it was dragging. Drove about 5 miles and slowed down for a car that was turning. When I accelerated the rear wheels locked solid for about a second and then it went on its way. Drove a few more miles and got to a place where I could safely test it. The lockup occurred several times again then I parked. it.
The only thing I can think of was the rear clutch pack clearance was rather tight. I should have ordered the thinner plates but in haste to get the car ready for a show I just went with it. Tried a variety of selective snap rings but it was still not where I wanted it.
Any thoughts on how to proceed? I was thinking about swapping the valve body out first to rule that out before pulling the trans. I have a nice turbo action reverse manual I can throw in it.