Hopefully someone can help me diagnose my TH350 problem. It will not engage 3rd gear in D. Here's what works: reverse gear is fine. Manual 1st gear is fine, manual 2nd gear is fine. So I can drive around all day long manually shifting from 1st to 2nd gear. But in D, it will drive fine in 1st, shift to 2nd, but on the higher RPM of 2nd, the RPM starts racing (e.g., it slips) and it will not go into 3rd. Fluid level and color is fine. vaccum modulator seems to be working. I'm hoping it's something simple I can fix on the car like the governor but I'm afraid it's internal. Any thoughts appreciated.

-Rob

this sounds like what happened to my iroc. ended up being my third and fourth clutch went bad.

Yep, trans needs fixin'. It does shift into third, you just don't feel it.

However, you might put a pressure gauge, 0-200 PSI min, onto the forward plug pass side of the case and check for oil pressure to the direct clutch. Good oil pressure, burnt clutches.

Welcome to the Club!