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Old 08-15-2016, 02:53 AM   #1
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Default Vacuum Modulator

I have a 1990 Oldsmobile Delta 88 Royale with the 440-T4 / 4T60 Transmission. I'm looking for an adjustable Vacuum Modulator for my car as I believe my old one is not functioning properly, can someone send me a link to one they recommend?

Thanks,

Matt
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Old 08-15-2016, 10:31 AM   #2
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Napa ATP 17783 is one choice. I put a napa unit in the park avenue years ago and haven't looked back since. Hopefully it'* still stocked.
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Old 08-28-2016, 02:22 PM   #3
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This came in via PM:
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Originally Posted by pjmia96
Hi rjolly87, I put the the Napa modulator that you suggested and it seems to shift funny when you step on it it feels very loose shifting from
First to Second gear and a little harder from 2nd to third gear.

My question is where do you recomend I have the vaulve screw set. Do looser shift raise the transmission temp or harder shifts?

Thanks,

Matt
It'* usually best to keep the mechanical stuff out of PM'* so that the forum can benefit from the knowledge shared.

I tightened mine about 3/4 of a turn. The shifts range from slightly firm when the car is running great, to slightly rude when the car isn't making the power that it should. I have also noticed that the shifts are more aggressive at higher altitudes, so I suspect the adjustment may differ depending on where you live. Adjustments really shouldn't be made more than a 1/2 turn at a time.

Also be sure to keep track of how much you move the screw, because it is very easy to get 'lost'. If you are 2-3 turns in, and your car isn't trying to self destruct at every shift, it'* likely you have a more serious issue.

Soft shifts cause more friction material based wear, and heat from associated slipping, where as too aggressive of a shift can cause a shock load through most of the drivetrain. The risk associated with the latter is a bit lower, but can be downright uncomfortable.
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