trans shifting problem
 

An easy test is to unplug the kick down(right rear of trans.black single pole plug) and see if it corrects the problem. If there is a problem in the switch under the gas pedal this will help eliminate it as the problem

My 92 300ce did just that one day. Shifted from 4th to 3rd ont he freeway, then if I stopped it would shift to 4th and back into 3rd after a bit of time.

Of course I immediately went to my mech, and on the way there, 4th disappeared all together, and 3rds started hinting at wanting to drop to 2nd.

I made it to my mech, and he found the clutch packs for 4th were gone, 3rd was almost gone, and basically it was time for the tranny to be done.

I ended up having him rebuild it for about $2500 less than the dealer wanted for one.

Cost me around $1700 but that included getting my springs installed, and all fluids changed.

In fact I'm coming up on my tranny fluid and filter change soon enough.

Alon

Downshift woes
 

Gentlemen.....Govenor pressure loss would certainly be a contributing factor as already stated, however, I believe if this were the case, the problem would not be so intermitent. T.V. cables do not usually go out of adjustment on there own. although the T.V. valve itself in the control valve body has many small plastic pieces and has been known to deteriorate. A faulty kickdown solenoid or constant signal to it would cause first gear take off and only full throttle upshifts.
The modulator is only for pressure control in relation to engine load...pressure rise and shift feel. If you turn the screw clockwise, you increase the pressure. If you do so it will firm up the shifts.
Should you notice an improvement when turning the screw in on the modulator, then more than likely you have a leaking or damaged K2 clutch, if this is a 3-4 shift concern. There is a hidden O-ring in the drum between the aluminum retainer and the drum itself. On earlier units the retainer is riveted to the drum. The O-ring gets hard from age and heat and cracks leaving a large leak.
I believe this is the most likely cause of your problem.
Regards;
Gerald

Where is this modulator? I include a picture of the underside around the autobox of my 190E

later,

Russ

modulator
 

on the left of the trans identified by a green or red color. It should have a rubber cap over the adjustment. It is right above the pan.

Phantom Downshift But No You Can't Replace My Transmission!
 

Sometimes our problems are really minor--but we launch into major repairs--and major expense. Here's an example of how easily this can happen.

I was driving down the I-10 in Southern California--about 75 MPH--and to my great surprise my 1992 400SE downshifted to 3rd. Oh no--transmission problems! This happened several times over the space of a week or so. Each time, I fiddled with the shift lever (3rd to Drive; Drive to 3rd)--but each time I was "stuck in 3rd"--engine revving madly--not able to upshift into 4th.

It seemed that parking the car for a bit restored things to normal. Then a few days later, the phantom downshift again. But now it was worse--the thing shifted into NEUTRAL--when I was at 75 MPH on a 6-lane wide freeway. I pulled off the freeway--got things working well enough to head to closest Mercedes dealer. At that point, I was convinced that my transmission was shot.

I described the symptoms to the Service Manager. A bit later, he gave me the bad news: (1) he needed to keep the car for a day; (2) I needed to come back next Tuesday--when the old mechanics are there (apparently old cars require old mechanics); and (3) it was going to be EXPENSIVE.

Back at home--what's this?--I discovered that the PAPER SEAL at the base of the shift lever was all crumpled up. Could this--I wondered--cause shifting problems? I madly goosed the shift lever back and forth--trying to assess the situation. Finally, I took a needle-nosed pliers and pulled all that crumpled paper seal out of there. PROBLEM SOLVED; EXPENSE $0. My transmission has been rock solid ever since. :)

But I gotta wonder--what would the Mercedes dealer have done? Also I gotta wonder, if any of the problems reported in this thread were due to nothing more than CRUMPLED PAPER.

LESSON LEARNED: If you experience "Phantom Shifting", check the condition of that paper seal at the base of the shift lever.

Paper seal? What paper seal? Was it interfering with the shifter?

Yeah, do tell all!

Ed! We're all wondering what you meant by this paper seal, please let us know. Thank you very much.

Follow-up on Questions About "Paper" At Base of Shift Lever
 

Yes, the paper was most definitely interfering with the shifter. By "paper", I am referring to that waffley-looking stuff that is visibile in the channel in which the shift lever is moved (i.e. at the base of the shift lever). It deteriorates--eventually mooshes-up (technical term)--and causes BIG problems.

Really interesting question is: "What diagnosis would dealership/mechanic provide--if this mooshed-up paper is the cause of the problem?" How many of them would catch it? How many would be honest about the--very simple--nature of the problem?

Maybe some brave soul with--with mooshed-up paper and time/patience to investigate--can run his/her car through some dealerships/mechanics and give us a report of the ranges of repair estimates that are received.

I've attached a photo--could not quite figure out how to embed the photo in this message.

1991 300CE tranny downshifts
 

I have a 1991 300CE 112,000 miles that I just bought. On the test drive it performed fine. After handing over the cash and 20 miles into the drive home, it downshifted, smoothly, into 3rd and stayed there. (I didn't even notice at the time.) I messed with the shifter (which has had the bushing pins replaced), putting in "3" and back to "D" with no result. Two times, the tranny went into neutral, each time I pulled off the highway, but then never went into 4th for the rest of the 100 mile drive home. It did go into 2nd one time, but after stopping, it went back up to 3rd.

Two things not previously mentioned with these other scenerios is that mine seems to have no 1st, and it never slipped. It had plenty of power throught the tranny, shifts seemed to be okay and at the appropriate time (maybe a little late), but I only had 2nd and 3rd gear. Does this give any insight into narrowing down if it is merely the vacuum modulator? Or possibly a cable adjustment? I really don't want to rebuilt the tranny on a car I just bought.

I have seen that these trannys are completely vacuum controled, no electronics. Is that correct? Hard to believe that in 1991, a car costing nearly $60,000 had a seemingly antiquated vacuum transmission control system!

Thanks!

300e 722358 shifting a little hard from 1 to 2 150Kmi
 

I have been reading on this topic and wanted to ask Steve Brotherton who has posted so many useful info on this:

The car is up on jacks (for other major repairs) and I have "easy" access to the transmission driver side where the vacuum control valve is located. Given that it has 150K (original) miles, should I replace the valve anyway as a future precaution, and proceed adjusting the new one? Or are these meant to last this long and should I try and adjust the old one (counterclockwise T turns?) first to try and soften the shifting from 1 to 2, assuming hat I have no vacuum leaks in the feeding line from the intake manifold?

THKS!