727 manual valve body-Reverse is slipping BAD, All other gears seem good

727 manual valve body-Reverse is slipping BAD, All other gears seem good - Pressure tested

MobileCustoms said
OK, so my transmission performed really great when I pulled the drivetrain out 2 years ago to paint my car. I had previously overhauled it with all the good stuff and billet servos from Oregon Performance, etc.

Now, it slips real bad in reverse. Just drove to down to my friend's garage today and put it up on the hoist to run some line pressure tests.
Got 270 psi at the rear port, 90 psi at the front port and absolutely nothing at the middle line pressure port.
Any advice or tips would be much-appreciated! I've tried my best to look up old threads and info that points to the same symptoms. Hoping it's just something funky with the rear servo but baffled as to what could have happened while it was just sitting. The ONLY thing that is new or different now compared to when I pulled it out is that i have a new torque converter from PTC and a new but identical flex plate ( my old one was cracked) I'm heading out to dinner right now but will be checking back in this evening.

Obviously the fluid level needs to be correct.

The VERY first thing I would do is pull the rear servo and check it for cracks and lip seal condition.
Then make sure the valve body bolts are down tight like they should be.
@fishy68 (Tracy) may have more on this.

The center test port needs to be checked while in forward gears, but these links should help you.
First one you put in the symptom and it tells you where to look (the valve body is one listed for slipping reverse)
A-727 Torqueflite Diagnosis Dial

This link shows where to test and under which conditions.
Note that the governor port says (should be equal to road speed)
This means as your wheel speed increases, so should the pressure, so at 50 on the speedo should show around 50lbs at the governor port. (exact match not a big deal)
Transmission Line Pressure - TCI® Auto