I just removed the EGR on my '86 300sdl and drove around the block. Immediately noticed hard shifts, was always smooth. Put EGR back and it's normal now. I did forget to plug the egr vacuum line but when I plugged it, it was smoother but still a bit hard. How is this caused? I know I didn't plug the line good maybe that is why. On my '92 300sd I removed EGR and I got smoother shifts.

Textbook case of a vacuum leak. Get the line plugged correctly and it will go back to normal.

x2

Get a golf tee or a metal BB and plug the line.

Some people will get a small BB that fits tightly and put it in the rubber line and plug it back in to the EGR to make it look like it works, but still disable it. This way when it comes time for inspection (at least in PA) you don't have to worry about a picky mechanic flunking your car because the EGR is unplugged.


You might have accidentally pulled the vacuum line from the 2/3 valve on top of the valve cover.

What is happening is when you disconnected the EGR, the vacuum line was leaking and not allowing the vacuum system to reach full vacuum. The vacuum system is a vital part of the transmission shift firmness, the hard shifts are in no way caused by the EGR system.

Just some things to check, hope it helps you out.


-Nick

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Thanks Gene and Nick. Im gonna mess with this tommrow and see what I can do.