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Old 11-15-2013, 01:08 PM
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Join Date: Nov 2013
Posts: 1
722.3x Very hard downshifting into 1st gear

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.

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Old 11-15-2013, 01:19 PM
sixto's Avatar
smoke gets in your eyes
Join Date: Jun 2000
Location: Eastern TN
Posts: 20,816
Did you lose tension on the Bowden cable?

87 300D
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Old 11-15-2013, 04:25 PM
Zacharias's Avatar
Not so amused
Join Date: Apr 2010
Location: West Quebec
Posts: 4,025
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.

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
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Old 11-15-2013, 04:32 PM
whunter's Avatar
Join Date: Dec 2003
Location: Metro Detroit, Michigan
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