I wanted to post an issue with my 722.303 transmission that showed up about a week ago. The transmission is in my '81 300SD and has about 250k on it. It had been shifting as most do, firm 1-2 and then a bit of flaring on the 2-3 up shift. However, one day the flaring stopped on the 2-3 up shift. All other shifts seemed slightly more jarring, but not so significantly that I would have noticed any change.

The really concerning issue was the 2-1 downshift. While braking from about 10+ MPH the car would slam very hard into 1st gear. After doing some reading on this forum I had hypothesized that the transmission vacuum modulator may have gone bad. It seemed this was a very common failure, but I haven't seen anyone mention the hard 2-1 downshift in relation to the failure.

I removed the vacuum line going from the VCV to the modulator and sure enough it was full of ATF. The modulator in my car was the original style with the metal band around the outside. I bought the replacement ($45), pulled the two Allen screws holding it on and replaced it. I haven't tuned it yet, but on the initial test drives it was shifting very smoothly throughout all gears and not slamming into 1st anymore.

I thought I'd put this out there to let anyone know who is having this problem that it is a very easy fix.

Did you lose tension on the Bowden cable?

Sixto
87 300D

Glad you got the problem solved.

However, for posterity (people coming on this thread later looking for answers) I want to note that there are at least one or two other possible causes for hard 2-1 downshifts, so what occurred in your case isn't necessarily typical.

I found when researching my own transmission problems (not related to this) that there were numerous "eureka!" posts both here and on benzworld where the contributors had cured the same problem that I had... none worked for me.

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

These links may be helpful to other members.

http://www.peachparts.com/shopforum/general-information/337640-1262704079_blue-722-418-vacuum-modulator.html

http://www.peachparts.com/shopforum/general-information/335721-722-xxx-transmission-vacuum-modulators.html


.

__________________
ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/