Hi I just installed my first self built TH400 in my Nova. It works good but shifts pretty soft, I was expecting a much harder shift. I am using a 10" TSI converter rated with 2800 stall and baloon plate. I am running John Deere low viscosity Hygard fluid. My engine is a 454 and I was testing it with the turbo putting out 6psi so I figure around 600hp at the flywheel.

I rebuilt the trans using a Hughes kit, set the clutch clearances on the tight side from Ron Sessions book. I installed a Hughes forward manual only VB. I did the dual feed internal mods. I didnt open the pump, it is completely stock. I checked the fluid level a bunch of times it is topped off.

The trans shifts quickly, at least quicker than the stock TH350 did, but it is still a soft shift. What are some of the things that would do this? Could the pump just be shot, I didnt touch it since the trans was in great shape when I tore it down.

Thanks for any ideas

Frank,
To be honest I usually don't provide support for a competitors product, but I know the lead trans guy at Hughes so I will in this case.

If you didn't open the pump up, you didn't rebuild the transmission...

There are pump gear clearances that need to be checked, the gears need to be inspected, the pump bushing and seal need to be replaced, and the boost valve needs to be inspected, as well as the PR valve movement.

TH400's are usually 30+ yrs old.

The Hughes forward pattern manual valve body is basically the same as mine.
I don't know the size of their feed holes or what they do with the 3rd accumulator but in any case, I doubt that the VB or calibration is the issue.

I would suggest putting a prerssure gauge on it. You will want to see 160 psi warm in gear with the modulator unplugged and 1000-1500 rpm.

If you see much less than this and/or a large pressure drop from hot to cold you have a worn out pump.