auto tranny vacuum

[steve bowen]

I have a '84 928s auto that's shifting a little strange, i'm sure its vacuum related or hoping so ,I have a three prong connector on top of the bell housing at the back of the motor, cant find where it goes? i'm famliar with vacuum modulators on American trannys & have tailored many to my specific shift points. it shifts very positive through every gear, but at times I have to lift off the throttle to get it to shift? I appreciate any help thanks steve

[Peter Bull]

The transmission on my '91 S4 had a similar behavior that was solved by adjusting what the workshop manual called the "throttle pressure cable". It is a cable that runs from the throttle linkage on the engine to the transmission. If the play in that cable is too big, or too small, the shifting gets strange.

HTH

/Peter

[MPDano]

Originally Posted by steve bowen

I have a '84 928s auto that's shifting a little strange, i'm sure its vacuum related or hoping so ,I have a three prong connector on top of the bell housing at the back of the motor, cant find where it goes? i'm famliar with vacuum modulators on American trannys & have tailored many to my specific shift points. it shifts very positive through every gear, but at times I have to lift off the throttle to get it to shift? I appreciate any help thanks steve

This is a known issue on earlier 928's. There is a small vacuum line (which disintegrates) and connects to a hard line that follows the torque tube and there is another small line that connects to the transaxle. Replace those two and you'll be golden.

[harborman]

"I have a three prong connector on top of the bell housing at the back of the motor, cant find where it goes?"

That might be for the ignition timing pick up.