87 300D Turbo at 3-4 shift it revs like mad, letting off the throttle allows shift

[rcwarship]

Hi All,
I just bought a 300d turbo & have been trouble shooting my transmission shifting & found that the vacuum was non-existent. After reconnecting several vacuum lines, I now have very smooth shifting 1-2, 2-3. When 3-4 shifts, the engine rpms climb & I have to let off the throttle to allow it to shift.

Do you guys suppose:

1. This is a linkage adjustment?
2. Vacuum?
3. Is this "flaring"?

Thanks & Best Regards,
Jon
1987 300D turbo
140k miles on car

[layback40]

Originally Posted by rcwarship

Hi All,
I just bought a 300d turbo & have been trouble shooting my transmission shifting & found that the vacuum was non-existent. After reconnecting several vacuum lines, I now have very smooth shifting 1-2, 2-3. When 3-4 shifts, the engine rpms climb & I have to let off the throttle to allow it to shift.

Do you guys suppose:

1. This is a linkage adjustment?
2. Vacuum?
3. Is this "flaring"?

Thanks & Best Regards,
Jon
1987 300D turbo
140k miles on car

1. probably not.
2. probably not.
3. yes.

[supercub]

It is flaring and can be reduced or eliminated by adjusting the shift point so that shifts later. It has something to do with too much fluid pressure in the transmission at the time of shifting. If your car has the cam system on top of the valve cover, check the plastic paws for wear.

[kerry]

Flaring can be minimized with less vacuum. Try removing all vacuum from the transmission and see if the flaring goes away. The shifts, especially the early ones, should become very harsh. If the 3-4 flaring goes away with no vacuum, then adjusting the vacuum or modulator should be able to eliminate the flaring.

[compu_85]

When you say it revs high... is it just staying in 3rd too long, or is the engine revving away like the transmission is in neutral?

If it is just holding 3rd gear too long I would start by checking the linkage. Actually I'd do that anyway because it's so easy. See this video: http://www.youtube.com/watch?v=z2tLAwJbpYg

You just adjust the cable length so that it is right at the "no tension" point with no throttle application.

-J

[winmutt]

Lets start with the basics. When was the last time you flushed it?

[rcwarship]

Thanks for the replies!

The 3-4 is revving like it's in neutral.

Basics are an awesome question. I'm starting at ground zero: no maintenance records, recent purchase......ironing out the bugs and starting to catch up on maintenance.

When purchased (3 weeks ago), the oil was clean, the radiator had good colored green anti-freeze, and the owner stated that he'd been keeping up on the maintenance. What that actually "means" though is anyone's guess.

Since I'm a noob & am having trouble getting my mind around the Mercedes shifting system - plus since I don't know what I'm doing, I need to start from the bottom & work through it. My plan to date:
1. Adjust throttle linkages - found a split ball joint last evening & have a replacement ordered.
2. Adjust VCV
3. Disconnect vacuum to test for flaring - thanks for the suggestion
4. Test vacuum - run tubing for a gauge inside of car & drive it
5. Bypass blue flying saucer - run directly from VCV
6. Transmission filter renewal - thanks for the suggestion

Any comments/suggestions/ are gratefully accepted.

Thanks again,
Jon

[winmutt]

Originally Posted by rcwarship

am having trouble getting my mind around the Mercedes shifting system

The shifting is pretty basic, more vacuum == more flare. Disconnecting the the vacuum is a great idea. When you start from stop do you floor it or gradually accelerate? If you are not flooring it, try flooring it and see if it flares in 1-2 or 2-3.


I suggest putting a 5 speed in there

[Orv]

If all else fails, putting it in "S" so you can manually upshift to 4th by selecting "D" when you're done accelerating will help. That's what I do in my '81; it will flare from 3rd to 4th if the road speed is less than 40 mph, which is a problem under light acceleration, since normally it wants to go into 4th at 25 mph.