GregBBRD

To set the pressure?

ammonman

+1 for Greg and his willingness to share transmission knowledge. Even though I could most likely complete a successful trans rebuild I'll send mine to Dr. Brown when the time comes. The benefit of his experience is IMHO priceless.

Mike

1989porsche928

yes to set the modulator pressure

1989porsche928

It is cold and raining outside in ny, but i am tempted to jack the car and remove the modulator.

1989porsche928

i should find out were that steve guy lives and drive to his house, i guess i could find all the 928 drivers with transmission problems and start an occupy steve group.

ammonman

There isn't a tool I'm aware of (other than a good old vacuum gauge to check the vacuum signal from the engine) that plugs into the modulating pressure valve and reads internal fluid pressures. You need a set of pressure gauges like to read the Modulating, Control (operating) pressure, and Governor pressures. Per the WSM, no up-shift is either an issue with the governor or the valve body. You can pull the governor with minimal loss of fluid. You will most likely need a new o-ring for the governor cover. The governor can be removed and serviced with the trans installed in the car.

Mike

G8RB8

Lots of info in this thread.
https://rennlist.com/forums/928-foru...ear-shift.html

GregBBRD

There are three ports, on the sides of the transmission, that have plugs in them, with aluminum washers between the transmission case and the plug. One of them is modulator pressure, one is governor pressure, and the other is system pressure. The WSM talks about them and the appropriate pressures.

The Mecedes "tool" is a set of gauges, so that you can see system pressure and modulator pressure, at the same time.

I believe that my "official" gauge set came from Baum Tools.

You might want to note that system pressure is a "fixed" value and governor pressure is a function of modulator pressure and throttle posistion (thus not adjustable). The only thing that you can change is modulating pressure.

If all you want to do is check the modulator pressure, I make up two different single gauge "kits" with the appropriate adpators (that I offer with a rebuilt transmission...or when someone changes a modulator)), that thread right into the port and read modulator pressure only. The hose is long enough to reach inside the car, from the underside, so that you can go drive around and check/set your modulator pressure. The gauges are fluid filled, to "dampen" the vibrations and slight pulses. The difference between the two different "kits" is the quality of the gauges. One has a basic 0-100 gauge (and you can pin it and ruin it, if there is something really wrong), for the "home guy" and is $99.95. The other is a much more robust (larger and more accurate 0-200 psi) gauge, for more frequent use (and tougher to pin and ruin.) It runs $169.95.

Makes setting the modulator pressure, initially, much easier.

1989porsche928

ater i pull the governor out how do i inspect it?

1989porsche928

Update:
Today it was to cold to pull off the governor.
In Park the vehicle is parked, in neutrol I can lightly press the gas to make it go forward.
Reverse does not engage.
In the selector 2, 3 and Drive will only put me in second gear.
Before I remove the bowden cable and kickdown solenoid relay it would go into reverse (i think this is another problem then the shifting) and stay in 2nd, but it would flare and not upshift.

1989porsche928

when i press on the gas in neutrol it is almost like pressing the clutch and gas down in first gear and making it move on a manual transmission

1989porsche928

hey that guy that made the post Help no sudden engagement in gears did not find out the problem

G8RB8

I think he's still working on it. I posted the link because there are links in that thread to pertinent information. Look for them.
His problem is different than yours. You probably have a linkage problem. His is likely the regulator, pump, or valve body.

1989porsche928

can any one explain this better, the manual says to put the car in N then unplug the shifter cable on the transmission, then move the selector to neutrol and reattach cable. how do I know when the selecter is in neutrol?

Landseer

As I said earlier, those that know will not share.
Its a void we will fix in the next year or so I suspect as more fail.
Same as the Mercedes of same era.
Mercedes holds its tech information closely.
There are some videos, though, that might help, for them.
They are not very special inside, BTW, and we will as a community solve it once we focus.