Pcplod

My car has just started shifting hard the last couple of days... It doesn't seem to be shifting at higher points, it is just shifting hard (like a kick in the back of the seat) almost regardless of throttle position or rpm level. The only shift that isn't really hard is the one into 4th, and that is hard unless I am just going through town slowly. Never had any transmission problems before, just driving nicely then one day started shifting hard.

I thought about adjusting the Bowden cable, but I am not sure how to. I see all sorts of articles that talk about adjusting the Bowden cable, but am still not sure how to adjust it. Do you take the ball off at the end where the four cables all come together and lengthen/shorten via the threaded part going into the rubber covered part of the cable?

Thanks, and sorry if this is something that has been done before and I just missed it.

SeanR

Sounds to me like a vacuum leak or disconnected vac line to the trans.

Pcplod

Where would I start looking for that Sean??

SeanR

Pull the air filter box and check all the vac lines there first. The one for the trans is usually visible on top of the bell housing. It ties in with all the other lines at the rear of the engine.

Pcplod

Great!! Thanks!! I will report back with my findings.

Lizard928

personally I go to the vacuum on the transmission. Pull the line off the (drivers) side of the transmission and plug my vac gauge into it. Then start car. If you have no vacuum trace back from there.

rexpontius

Yep, 99% sure its a vacuum issue.

Pcplod

Hey Lizard, how do you get to the vacuum on the transmission? Jack up the car and crawl under, or can you get to it without jacking it up? Also, is there only one vacuum line under there to work with?

Sorry, but I am still a newb on a lot of these things, and I can only learn if I ask. ;-)

Lizard928

I'm slimmer than most and can slide under the back pop it off and measure it.
Though most times a hoist is best.

Pcplod

Thanks Lizard! I will do some checking tomorrow and post my findings. I appreciate all the help (as always)!!

Leon Speed

Or low ATF level

MainePorsche

First check the vacuum 'T' under the airbox -> this is the vacuum origin. Remove the line and hook your measuring line to this -> engine on and note the vacuum. If good here then check the line to the transmission at the transmission. There should be a braided vacuum hose coupled to the vacuum modulator (a green face with a black cap on it). You may have to remove the cap to get your fingers on the line. Be sure to treat this cap fairly, as if you violate it, the modulator won't hold vacuum. When your measuring line is on the modulator, with the cap on, measure to see if it holds vacuum. Be deduction, find where the vacuum fault is. A new modulator is about 30+ dollars.
While your down there check the ATF level. You should do both with car up and level -> much easier.

Edit: thought I'd add this pdf page as it may be helpful.

Pcplod

Very helpful....thanks Maine!

Pcplod

Well I must be fatter than I thought I was (or maybe my car is lower), but I can't get underneath it to check the vacuum and ATF level with it on the ground!! However, I did find a little pool of what I think is ATF under the back of the car. That points toward a low fluid level, but now I have to find out where and why it is leaking....I might be visiting Mo very soon.

MainePorsche

Yes, any work under a 928 must have it raised. There is no clearance to work.
For ATF level check, and adjustment, she must be level. When was the last time ATF was serviced ? I would still have a look at the vacuum to the modulator -> once you have it up, you might as well do this -> not difficult and will get it out of the way for it will have to dealt with at some point. Preventative measures are a good thing on this car.