85fortheDrive

We had a TB/WP job done on our 85 auto which included swapping in a Porken tensioner. Since that time, the car shifts somewhat unpredictably, especially when cold. I frequently have to let off the gas to get her to shift 2-3 and 3-4. Car now regularly revs past 3k rpm before shifting. Hasn't done that before, but I'm left wondering if this is a more correct shifting pattern or if it represents a problem.

I pulled the airbox and tested vacuum through the transmission line, front to back. It held vacuum.
I also slightly tightened the Bowden cable.

We don't have a lift, and crawling under the car to locate and trace the transmission vacuum line seems daunting, especially with all the heat shields blocking the view. I know some have shared their experiences in replacing the plastic and braided portions of the line - I have read those accounts.

Any suggestions?

THANK YOU!

Mrmerlin

need some pictures of the throttle quadrant .

Get the WSM and verify the bowden cables are all properly adjusted.
did they remove the radiator? if so then they might have drained off some trans fluid.

NOTE check the trans for low fluid or kickdown cable has come out of adjustment or the vacuum system has a leak,
the vacuum modulator has failed , or a broken K 1 spring in the trans,

85fortheDrive

Here are the cables.

Bertrand Daoust

Good information here.
Maybe your Bowden cable is too tight.
See the two last lines of post #1.
Auto Transmission Adjustments - Rennlist - Porsche Discussion Forums

Mrmerlin

Make sure the hose clamp tail wont touch the throttle rod locknut .
Use the WSM to make sure the cables are properly adjusted.
Check trans fluid level with the engine idling and warm

Petza914

...and make sure to replace the reservoir cap BEFORE turning off the engine.

85fortheDrive

Thank you. The mechanic did top off the trans fluid reservoir. May I ask why it's important to replace the cap with the engine running? Not sure the mechanic did so.

Petza914

Because the fluid will overflow the reservoir once the engine is shutoff. If he topped it up with the engine off, there isn't enough fluid in it. Needs to be warm and level, then fill to the max line on the reservoir with it running, then replace the cap and shut off the engine.

Mrmerlin

usually you replace the cap seal unless the cap was overtightened, then it will crack and leak..
NOTE the cap has a 17 mm nut molded into its top,
so a small box wrench can be used to snug it and open the cap.