as i read in the threads to use Mobil 1 Synthetic oil in the tranny. I searched it in my country UAE and i got Original Mercedes Benz ATF only that costed my some $5.5 per liter. I drianed the tranny and the converter and added the new oil. Still i am not feeling good quality in shifts. even i rotated the vaccum modulator 5 clicks counter-clockwise, i still feel the hard shifts.

shams
150K 230E 1989

Is it possible that your transmission modulator valve does not hold vacuum any longer?

How about your all your vacuum hoses? Are they holding vacuum, or do you have a leak somewhere? Are they connected to where they are supposed to be connected? Do you have enough vacuum?

If all the above are OK, keep turning the adjustment key on your modulator valve counter clockwise more. You should feel it begin to soften. BB

don't know how to check vaccum. Are there any symptoms of vaccum leackage.

what about adding Mercedes original ATF instead of Synthetic Oil, is it ok??

You will need a vacume gauge to check that the modulator is getting vacume. You can get a cheep one from a department store for under $10.00 US. All you do is disconnect the vacume line at the modulator and plug in the vacume gage. I havent done this in a while so check my numbers but I belive you should see more than 18" vacume at idel. To check the Vacume modulator you will need a vacume pump. You just connect it to the modulator and pump up a vacume and see that it will hold. You can get a cheep one of these from and auto parts store for about $30.00 US. But be carfull the cheep ones tend to leak down themself giving you a false indication. Even the good ones do this occasionally. So you need to test you vacume pump before you start by holding your finger over the vacume pump inlet and applying the vacume and makeing sure the pump holds vacume all by itself.

John Roncallo

1. does vaccum leakage cause hard shift?
2. why there is a minor clunk sound on shift down from 4 to 3
3. taking off the throttle pedal, it shifts to next gear at low speed

I'm not an expert with MB transmissions but typically in the old American lead sleads with transmissions using vacume modulators, loss of vacume to the transmission will cause the shift to occur as a higher than normal speed and be hard.

The other two symptoms I cant comment on

John Roncallo

Originally Posted by shams13
1. does vaccum leakage cause hard shift?
2. why there is a minor clunk sound on shift down from 4 to 3
3. taking off the throttle pedal, it shifts to next gear at low speed

1. YES.
2. Possibly lack of vacuum causing harder shift and/or loose/worn flex disk(s) or mounts.
3. A Bowden cable is used to monitor pedal travel, lifting pedal will allow upshift sooner.

Please read this article, almost everything you need has been written by SteveB.

http://www.continentalimports.com/ser_ic20242.html

Best Regards,
Jim

Install a vacuum gauge directly to the modulator vacuum hose, with the engine running there should be a steady reading of manifold vacuum present 14” to 22”HG. A quick opening and closing of the throttle should drop the vacuum to below 5” if not fix the vacuum problem first. If you have the proper responses, then install a pressure gauge and read working pressure. With the vacuum hose removed from the modulator and the car running at idle in drive hot, the pressure should read between 70 and 90 psi. Higher then 120 psi you could have a stuck pressure regulator valve (valve body) or a stuck modulating valve behind the modulator.