Can someone tell me definitively which way to turn the adjustment tab on the
transmission to produce a firmer shift. When I take the vacuum line off
shifts are more like being kicked by a horse than firm shifting (I don't know
if that indicates something?). I turned it clockwise and it made the
quite long. Now I have turned it counterclockwise then clockwise and
counterclockwise etc. and would like to know which way is firmer.
Clockwise tells the trans that you want later and firmer shifts.
Counterclockwise tells the trans that you want earlier and softer shifts.
The modulator is the round device on the driver's side of the transmission. On the 928, it affects only the quality of the shifts - no effect on the speed at which the shifts occur.
When you find it, first thing to check is that you have manifold vacuum on the line at the modulator. If you can hook a vacuum gauge to the line, the pressure should be perhaps 15 - 16" at idle. The pressure should drop sharply when you pop the throttle open, then peak sharply as you abruptly close the throttle.
Any ATF in the line is cause to replace the modulator. The modulator can be adjusted by removing the rubber cover, pulling the "T" handle out and turning it. The modulating pressure for your car should be 61 - 62.5 psi. One turn of the handle changes the pressure by approx. 6 psi, so the adjustment is pretty touchy. If you set the pressure too low, you can damage the transmission thru slippage.
>I have a 1983 928S and the Transmission Modulator on the drivers side of the transmission was leaking. Before I had it replaced the transmission shifted tight. Now the transmission flairs between shifts. Is the modulator adjustable?
> Ron Johnson
The modulator is adjustable. Remove the cover on the modulator, and slightly
pull out the adjusting key underneath. Turning the key clockwise raises the
pressure approximately 2.8 psi per turn.