Newbee needs help. My vehicle is a 1981 300d with auto trans. I purchased the vehicle with the intent to restore the car. The problem is that the transmission shifts hard.

It seems from reading posts that this is most likely a vaccum problem. Seem to be the consenus that it is from the (what I call) black box on top of the engine.

However, the posts do not seem to address my specific problem which is that the vehicle will shift automatically but 1-2 is hard (will make head move) , 2-3 very noticable (will at times make tires chirp) and the reaminder are at high rpm.

If I let off the gas before the shifts the car will shift much more smoother if almost unnoticable. 1-2 by 10 mph, 2-3 by 25-30 mph and 3-4 at 40-45 mph.

Please help with this dichotomy is it a manual or auto?????

Also, the ac/heat, door locks, windows and other accessories (vac controled) all work properly.

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Brandt Taylor

same exact problem ehere. when its cold the shifts jar my head. I'm worried it going to damage the tranny in time and its embarassing for me when others are in the car.

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1993 Benz-190E-2.6 liter

There is a vacuum line from the transmission modulator on the US driver side of the transmission that goes up to the a device on the back side of the injection pump. At leas on turbodiesels that's where it goes. Make sure that vacuum line is in place and intact.

It's not uncommon to knock that line out of place when changing the oil filter.

Sixto
95 S420
87 300SDL

Clean the line out with brake fluid. Take it off the car first and let it dry before reinstalling. If something is interfering with the vacuum the car will shift harder. With more vacuum it shifts softer. So you sound like you have a lack of vacuum. Check and clean all the vacuum hoses and make sure they are seated correctly. Make sure you have no leaks in the vacuum system. Clean all the hoses. Take the black plastic cover off the top of the valve cover and see what condition the hoses and white switches are in. They can wear. The plastic can wear away on the switch, which prevents the cam from actuating the switch at the correct time.
Check the vacuum line connection into the transmission. Make sure it is not blocked or disconnected.

Dave

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1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car

Possible but unless you have a donor car for parts it'll cost less to have your AT serviced or even rebuilt by a competent shop.

Sixto
95 S420
87 300SDL