TH400 2-3 Upshift Problem

[TheBandit]

I have a TH400 behind the 355 in my Nova. The internals are of unknown history, but I can only assume it has some sort of shift kit in it because it shifts very firm. During normal cruising it shifts fine, but at WOT it wont shift 2-3. I have taken it to about 6,500rpm at WOT and held engine speed by backing off the throttle a little and it still will not shift. I have to back off the throttle quite a bit (increase vacuum) to get it to shift. I have no kickdown switch right now.

What should I be looking at to troubleshoot this? The governor? Vacuum signal / modulator? Do I need to wire in a kickdown switch?

Thanks for any advise.

[waterdog]

I'm curious about this one myself, one of the several 400s I've put in my brother's car did the same thing. The transmition shop told him it was because it didn't have a shift kit in it, so I pulled it out for them to go thru it and don't think that was the reason. When he bought it, it supposedly had everything in it. Walt

[Bob West]

Put a manual valve body in it, then it will shift If you ever step up the power you will be glad you did

[John_Heard]

Does it have an adjustable vacuum modulator valve in it? Some kits have those I think, seems like there is a allen head screw inside the vacuum port on them to adjust. Memory's kinda dusty on the subject though...

[TheBandit]

Well the car is street driven and I do like driving around in auto most of the time, so the manual VB is out.

The vacuum modulator is adjustable and I've used it to bring down the shiftpoints a lot for when it's just cruising around town. But it doesn't seem to affect the WOT shifting in drive/auto, only part throttle shifting.

Any other ideas?

[TheBandit]

Still have the same problem. Is it possible the governor needs to be cleaned out or replaced? Or maybe this has to do with needing a kickdown switch?