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Old 10-22-2018, 07:16 PM   #11
ss3011
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Default Re: Turbo 400 experts please step in....

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 .
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Old 10-22-2018, 07:25 PM   #12
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Default Re: Turbo 400 experts please step in....

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.
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Old 10-22-2018, 09:34 PM   #13
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Wink Re: Turbo 400 experts please step in....

Quote:
Originally Posted by Mark Ugrich View Post
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.
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Old 10-22-2018, 09:55 PM   #14
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Default Re: Turbo 400 experts please step in....

Quote:
Originally Posted by ss3011 View Post
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.
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Old 10-22-2018, 09:58 PM   #15
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Default Re: Turbo 400 experts please step in....

Quote:
Originally Posted by Mark Ugrich View Post
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.
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Old 10-22-2018, 10:18 PM   #16
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Default Re: Turbo 400 experts please step in....

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Originally Posted by joespanova View Post
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.
The solenoid will delay the upshifts past the 0 vacuum shift point. You can leave it disconnected as the line pressure is controlled by the modulator only but you will get early full throttle upshifts and no kickdown.

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Old 10-22-2018, 10:20 PM   #17
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Default Re: Turbo 400 experts please step in....

Quote:
Originally Posted by joespanova View Post
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.
Joe, It's hooked to a n/o switch that only passes 12v at WOT, so ,about 99 % of the time, it's not doing anything anyway. So yes , you can leave it unhooked.
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Old 10-22-2018, 10:37 PM   #18
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OK , thanks everyone for your contributions.
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Old 10-23-2018, 11:35 AM   #19
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Default Re: Turbo 400 experts please step in....

Thinking about this a bit more . The kits you can buy just modify the secondary weights and springs of the governor . Your problem is at slower speeds that may be affected by the Primary governor weights , this is the heavier weight . I would look for a different governor that has a Lighter primary weight . Suggest you find one with a big hole drilled through the primary weight and swap it on to your existing governor . Reuse the secondary weights and springs you already have but swap on a pair of the lighter primary weights . See what the effect is to that change is . Some trans shops have used governors you may be able to purchase cheap , and maybe even the pins . We had many , many different governor weights designed , both primary and secondary . Good luck ! BTW when you adjusted the modulator , did you see any effect ?
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Old 10-23-2018, 11:52 AM   #20
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Default Re: Turbo 400 experts please step in....

Also , you can use some T350 governor parts .Weights, springs. The top is different and the plastic gear turns the opposite way.
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