86'928S MeteorGrey

Went to check vacuum to the modulator today. It's been shifting a little early and hard. I didn't find and vacuum leaks, but did find that the Bowden cable was VERY loose. I turned it tighter by about 6 turns (about 1 mm play at the throttle plate). It was like the car woke up from good to great. Shifts smoothed out and shifts are close to red line when stabbed, and smooth/firm when cruisin'... I had been playing out a supercharger in my head, but now I think I'll be happy for a while. TGFRL!

928mac

Awesome news Mike, something everyone should be aware of

tailpipe

does this work on a 79 also ? details?

AO

Whatever you do, do ride in a SC'd car or you'll NEED a SCer.

Glenn M

What Andrew said!

Mike Frye

I'd also like to add that everyone should check the throttle cable as well.

I didn't think it was much of a big deal as long as the idle switch triggered when I stepped on the pedal (since you can't adjust the WOT part of the TPS).

Well it turns out that if there's any play in the throttle cable not only will you have a little less than immediate throttle response on acceleration, you may not even be triggering your WOT switch. I had tested the switch by pulling the cable from under the hood (because then I could test it with a VOM) but I hadn't tested it with the pedal by metering at the LH.

Unless you've got everything adjusted and all of the slack out of the throttle cable you're not getting a true idea of what the car can do.

Tom in Austin

Since you brought it up, what is the procedure exactly for adjusting the bowden cable?

86'928S MeteorGrey

I believed I had a vacuum leak to the modulator, because it's so common. I searched quite a bit on RL for other fixes and proceedures... I decided to go with the advice on this link from Leslie.

https://rennlist.com/forums/928-foru...mission+thread

My plan was to first make sure I had vacuum to the modulator, then troubleshoot other items. Since I found no vacuum leak to the modulator, I started Leslie's procedure.

The first step is to adjust your bowden cable until there was 1mm of play. I had heard previously that a loose bowden cable would cause your tranny to shift to early. After making the adjustment (pop off ball cup, use 7mm and 8mm wrenches to loosen the jam nut, then tighten the cup to provide approx. 1mm play. retighten the jam nut and reinstall the cup. In my case it was about 6 to 8 full turns... It was very loose.)

I took it for a spin and all of my issues have been corrected. Early shifting... Gone. It's still very firm shifting at full throttle, close to redline, but I believe this is how it's supposed to shift. Previously, I got early, harsh shifting all the time. By the symptoms, I thought for sure it was a vacuum leak. I may need to adjust the pressure a little, but I think I'm pretty happy with it right now.

I'll avoid riding in SC cars like the plague. I'm happy right now. (Maybe I'll go for some SC rides after Christmas...)

Tom in Austin

WSM page 37 - 115 says "Adjust spherical head of control cable until cable can be installed without strain"

"Without strain", what does that mean? Not tight? Loose?

Something lost in translation there!

Landseer

I read it as you pop the cable on the ball and there is no slack. Then from there, interatively remove, tighten to your taste and refit.

Too tight gives late shifts.
Too loose (usual condition when you rescue one from an elderly owner) and it rapid-shifts, so you are going 30mph or so in 4th.

Tom in Austin

Ah, much clearer now ;-)

karl ruiter

Something easy you might try is to replace the rubber cap on the modulator. I did this recently and it made a huge difference. 5 minute operation, dont have to pull down the exhaust or head shields or anything. I purchased a new modulator from Roger, but so far just installed the cap.