Tony

Just hooked up a gauge this afternoon to see if i could find anything out of the ordinary.

Attached to the test port on the passenger side (US) of the transmission just in front of the fluid res.

Started the car in Park and then cycled into Reverse..Neutral..and DRIVE and then back.

From what i gather the test is done in DRIVE with the vac line unhooked from the modulating valve on the side of the transmission. In all the manuals i have i cant seem to find what the operating pressure should be?


My issue is no up shifting into 3rd or 4th gear...and when it does it will often slip out of 4th...into 3rd...and even into 2nd. Not good on the freeway!

It seems to be worse as the transmission gets warmer which indicates to me a "sealing" issue somewhere as the viscosity of the fluid changes.

The gauge goes to 300psi and you can see it goes well over that on the test when in gear..

Seems to sit around
50psi in PARK
over 300psi in REVERSE..
75psi in Nuetral..
over 300psi in Drive..

Any input....????
I want to get an idea of whats going on first before i pull it and replace it.

MainePorsche

Tony,
Here's a page from the Mitchell trans pdf that I have. I can't upload for it is to large. I am trying to find my link to it. Hope it helps.

http://www.w124performance.com/docs/...2_Mitchell.pdf

Tony

Im well above all those numbers!

MainePorsche

Sorry Tony. I have no idea on the innards of the beast. I had an Operating Pressure of half of what it should be, and this resulted in absolutely no gear engagement. I was thinking of my pressure regulator valve. I was thinking the faulty regulator valve which probably resulted in some band, or other internal damage. For the sake of preserving the car, I opted to put in one of Greg's new units. Having somewhat of an elevated pressure is a mystery to me. What type of symptoms are you having ?

Tony

no upshifting to 3rd from 2nd...or from 3rd to 4th

If it does go to 4th it will often slip out of 4th into 3rd...or even 2nd.

MainePorsche

I hate to ask such an elementary question, but is your control pressure control valve cable ('Bowden cable') set properly relative to the throttle cable ? I'm just running through my fertile imagination that if they're both (way) off, the transmission will react relative to speed, rpm, and the control pressure control valve 'positioning'. Just a thought from someone with moderate experience here. Some of the Masters will chime in here I'm sure. I will follow with interest.
Best Wishes.
Craig

ammonman

Working pressure test conditions per the WSM are:
ATF Temp +80C
Trans in "D"
engine speed =1400rpm
Hand brake and and service brake applied
Vacuum line disconnected
Test for no longer than 5 seconds

Pressure should be between 220.5 and 250 psig.

Hope this helps.

Mike

Landshark87

Bowden cable adjust fixed flaring on mine, but still have hard shifts - at the shop now, getting new vac line to modulator, new modulator, K1spring, and B2 piston. Good luck with yours .....

Landshark87

i gave this to my mechanic (M1 modulation pressure - says 61-64.5psi):
http://jenniskens.livedsl.nl/Technic...5/MyTip584.htm

ammonman

There are three different pressures that can be checked on the A28.x series transmissions: working pressure (aka operating pressure), governor pressure (road speed dependent), and modulating pressure (engine load dependent). The only one that is adjustable externally is modulating pressure. Working/operating pressure is basically the primary pump output pressure (with an over-pressure bypass of course). Adjusting the modulating pressure affects the other two pressures but they aren't independently adjustable.

Mike