No manual downshift :(

[KnobMuffin]

I have a VP series 2 automatic and when I pull the lever back into second it does not down shift. It doesnt even manually shift to first when I pull the lever all the way down doing like 60k's. My 1988 Pontiac Firebird service manual has some info on the TH700-R4 and it reckons that it could be the valve body assembly or the input clutch. Is anyone here real good with transmissions? Is there a test I can do to pin point the problem.

You can download the service manual here: 1988 Pontiac Firebird Service Manual (phox) (download torrent) - TPB
It has alot of info on the TH700-R4 including complete teardown, inspect and rebuild.

[wildss]

i had this issue with a rebuilt box, trans builder said it was the valve body