722.315 slow to engage forward when warm - Page 2 - PeachParts Mercedes-Benz Forum

KAdams4458 · #16 01-10-2013, 11:43 AM

Your assumption is correct; I have tested and inspected the vacuum system and components. The modulator is the second revision, but is working. Paperwork suggests it was last replaced in the early 90's at a dealership in Arizona.

As for the fluid that I drained out, it smelled a little old, but not terribly burnt. Just a bit darker a d browner than I ordinarily would like to see. It wasn't black, or anything. I drained the converter and pan at the time without doing any kind of flush, so there would still be traces of the old stuff in there. A second drain and fill couldn't hurt.

I ha we not been able to test line pressures, yet. I have an appropriate gauge and banjo fitting, but no hose at this time.

Stretch · #17 01-10-2013, 01:38 PM

Unfortunately it seems as though that whereas the 722.1 transmissions suffer from problems at the front (front pump; torque converter etc) the 722.3/4s seem to suffer more with problems in the backend - governor...

...however, as stated previously pressure (fluid and vacuum) measurements are the first step to determining problems.

Do you need the pressure data?

KAdams4458 · #18 01-10-2013, 01:52 PM

It's in the FSM somewhere. Offhand, I have no idea what the fluid pressures should be. I vaguely recall reading here that someone used cheap, readily available plastic tubing to hook up the gauge for the test. I do have a 0-100 psi fluid pressure gauge on hand, though.

Diesel911 · #19 01-10-2013, 01:52 PM

I accidentally disconnected the Vacuum Line at the Transmission Modulator and when driving it changed through all forward and reverse gears in a normal manner.
Where I had issue was extremely harsh down shifts.

When you hook up a Gauge to check the Modulator pressure you disconnect the Vacuum Line from the Modulator you drive it at around 30mph and measure the pressure.

Both of what happened in the above cases clearly implies that with no Vacuum you can you should still be able to move forward into First Gear in a normal manner.

KAdams4458 · #20 01-10-2013, 01:55 PM

Quote:

Originally Posted by Diesel911

I accidentally disconnected the Vacuum Line at the Transmission Modulator and when driving it changed through all forward and reverse gears in a normal manner.
Where I had issue was extremely harsh down shifts.

When you hook up a Gauge to check the Modulator pressure you disconnect the Vacuum Line from the Modulator you drive it at around 30mph and measure the pressure.

Both of what happened in the above cases clearly implies that with no Vacuum you can you should still be able to move forward into First Gear in a normal manner.

That is my understanding as well. I have also driven this car to the parts store with no vacuum to the modulator, so that I could buy a piece of vacuum line to reattach it. It shifted normally through all four gears... just harshly.