1991 300CE transmission slipping out of 4th gear
 

I posted this question a bit earlier - changed the trans fluid and filter since then (within the last 1500 miles - car has 86K). Just started doing it again today - difficulty shifting up into the final gear and will then slip out. Only acting up in shifting from 3rd to 4th and then once in 4th - no other problems noted anywhere else along the shift range (although shifting is a little rough as I think my linkage somewhere is off...).

Is there any thing OTHER than a bad transmission that could account for this problem? Thanks.

Ryan

Anyone?? Is there a chance that this could be a linkage problem? Maybe a vacuum issue?

I was about to reply to your thread. I just been helping someone else with the 722.6...On another thread.

Now, yes it can be a vacuum. Put your car on ramps and unplug the vacuum line from the modulator. Start the car and feel the vacuum when you accelerate.. on the vacuum line. If oil is dripping from the vacuum line, the modulator must be replaced.. Feel the modulator if it is not loose....

Here are some documents that may help, but find master.pdf, and look at the troubleshooting section-See the first link...of post2

1996 S280 Australia transmission no reverse diagnose & rebuild. - Mercedes-Benz Forum

All the best,

Martin

Thanks, Martin.

I found the pdf - will check it out.

ryan

Just got around to testing - following Martin's post. I pulled the line and see no evidence of trans fluid, hooked up vacuum gauge to the hose and started car - pretty 17-18 psi as car idles. Rev it and drops to 0 and then responds as I let up on throttle...so I think that part is ok.

Pulled a vacuum on the transmission modulator and it does not hold a vacuum at all. I can hear someone clicking/moving inside the modulator upon initial application of vacuum, but needle drops off very quickly.

I'm assuming this is bad - right?

Ryan

Sounds like a leak to me... It would be the first item of attention to replace it as all these modulators have is diaphragm like any vacuum motor on a car?

Your replacement must be the same color as the old piece(very important).

The attachment from this thread from post 8 may help:

http://www.peachparts.com/shopforum/tech-help/348463-300te-722-358-tranny-3rd-4th-gone.html

All the best,

Martin

Thanks Martin. I have checked out that attachment and remained confused about the correct modulator. That one seems to indicate a red one for my 777.359 transmission and I currently have a black one installed. I have attached a pic below of the new modulator that is indicated on all online parts sources as being for my vehicle - notice it has a plastic cap and my current one has a black rubber cap - but it seems to have a different pin than what shows up when I look up the pin part for my application (pic attached).

I'm a little confused, but am guessing that Mercedes changed the design?? Should I buy a new pin and use with this new modulator?

You know, A lot of this drawings/photos to parts from online retailers do not always match up to the item...

The modulator and pin looks identical what a 722.5 comes with...

I would order the pin too..See what you get...?

Martin

Ok, that was my plan! Thanks.

ryan