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

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.

This came in via PM:
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.