I finally got around to finishing my build so I decided to test out the trans before getting it tuned because I only been driving into the garage and backing into driveway. But to my demise its always something. I have a fresh rebuilt rmvb th400 and park, reverse, neutral, and 1st gear work. Once shifted into second gear tires lock up and same for third gear. Fluid is good and shift linkage has been triple checked. I seen 1 other post about this but no questions where answer and post just feel off. If anyone has the knowledge of letting me know what's going wrong. Or has experienced this before i would greatly appreciate it.

 

Sounds like a one way sprags is in backwards. Thinkin maybe the one for the direct drum??