Turbo 400 experts please step in....

[Jim Cimarolli]

Originally Posted by Mark Ugrich

Check the vacuum at the intake as well. It’s been a while , but from my training during GM tech school, govenor pressure overcomes modulator pressure to make the shift. Someone correct me if I’m wrong, but I don’t think disconnecting the downshift solenoid will have any effect on shift timing.

X2, I agree.

[joespanova]

Originally Posted by Mark Ugrich

Check the vacuum at the intake as well. It’s been a while , but from my training during GM tech school, govenor pressure overcomes modulator pressure to make the shift. Someone correct me if I’m wrong, but I don’t think disconnecting the downshift solenoid will have any effect on shift timing.

Sorry for the confusion. The reference to the solenoid was about whether I can leave it disconnected and if that has any consequence . No connection to upshift timing.

[joespanova]

Originally Posted by ss3011

Some how I thought your post was to set the shift points at WOT . It is harder to set the part throttle shift points . The modulator system basically makes a pressure to tell the transmission what load is on the engine . This is based on manifold vacuum . The lower the vacuum the higher this modulator pressure would be . So if you have an engine with high vacuum at idle , and you lightly drive away from a stop , you get a very low modulator pressure and therefore a early shift point . A hot rod engine might have a fairly low idle vacuum and if you did that light throttle drive away , you might get a delayed shift . So most hot rodders put a high stall converter in place of the stock tight converter , and what happens is the manifold vacuum is much higher than it would normally be , creating a low modulator pressure and an early shift . Most of the newer transmissions that are built now have electronically controlled shift patterns . They don't shift based on manifold vacuum . Before electronics there were cable controlled transmissions , like the 200 THM or 700-R4 . There were many different modulators to deal with different engines , with different manifold vacuums , but not anymore . The adjustable modulators are really not for you to adjust , but to set the modulator to a factor specification . There is not much you can do with your current vacuum modulator system . One thing you might try is a B&M Modulink , which basically converts the vacuum modulator to a throttle cable controlled modulator . I worked on a similar system for the Hummer , which was a diesel , so no manifold vacuum .

Thanks , your friend was correct., you know your stuff..........yes this is about "part throttle" shifts.

[joespanova]

Originally Posted by Alan Nyhus

How much vacuum do you have at the modulator? -Al

The idle vac is 10"
From experience I know if the mod isnt connected , it wont shift.
That being said I would think low vac would make it MORE reluctant to shift.
No one has addressed the kick down solenoid? IF I dont care about kickdown , then its not required to be connected.....somewhere I read where the solnoid increases line pressure in kick down mode?