I have an '87 W210 2.5 turbo that has some trans shifting problems:

When I engage in D and attempt to drive away, about a second or two after I step on the pedal the trans engages with a harsh jerk. Shifting from 1-2 seems ok, 2-3 has a bit of flare and 3-4 has lots of flare.

I have changed the trans fluid, filter, modulator and the pin behind the modulator (the pin was broken). I have also adjusted the 'bowden' linkage to take up all the slack with the throttle positioned at idle.

I think part of the problem is the wear in the trans itself, but I would like to rule out vacuum problems. I am trying to find information on this particular model but seem to get nowhere. Can anyone help?

I would like to test the operation of the trans vacuum amplifier (the blue thing on the firewall), but need directions. I have a snap-on vacuum tester that I can use.

Can anyone help me with some directions please?

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'98 E300 DT
'87 190D 2.5 turbo RIP
'92 S500 Sold
'03 3.2TL-S A-Spec

Search on it. There was a recent thread in which Brian was helping someone do just this.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Does the engine rev freely and then suddenly engage, or does it start to accelerate and then suddenly jerk?

The first sounds serious, the second sounds like a delayed downshift into 1st (supposed to stand in 2nd, then shift to 1st when you launch).

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Gone to the dark side

- Jeff

Can you pull a vacuum on each of the 4 ports and let me know what you get.. 3 of my 4 hold vaccum and one does not..

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Bill

Backyard Shadetree Mechanic, 30 years running.

1987 300TD
1988 300E (sold, sniff)
1999 S320
1981 Volkswagen Rabbit Truck (Diesel)
2001 Ford Expedition
1988 Suzuki Samurai
On my list to buy: R129, for me, and a R107 for my wife.

There is a "TRA" port on the top of the amplifer.............T into this line with the Mityvac and see what the vacuum level is at idle. If you can route the gauge into the vehicle and take it for a test drive at various pedal positions, that would also be helpful.

The pedal positions are as follows:

Idle

Moderate power (about 1/2 pedal)

Heavy power (about 3/4 pedal)

Maximum power under full boost.

Didn't I already explain why this occurs?

No, last we spoke I was to get back with you on the same info that you just asked for from shingleback. You never said if that 3 out of 4 ports holding vacuum was normal or not. BTW, wife has been hogging the car now that I have the new EVAP/Heater core in, otherwise I would have gotten back with you...

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Bill

Backyard Shadetree Mechanic, 30 years running.

1987 300TD
1988 300E (sold, sniff)
1999 S320
1981 Volkswagen Rabbit Truck (Diesel)
2001 Ford Expedition
1988 Suzuki Samurai
On my list to buy: R129, for me, and a R107 for my wife.

Whether they hold vacuum or not is of no direct consequence. In fact, they may not hold vacuum unless all the ports are capped..........they are somewhat interconnected internally.

The fourth port is designed to accept manifold pressure and adding vacuum to this port may damage the unit...........so, I wouldn't advise it.

When you finally get the data, we'll sort out your issue on your thread.

Thank you to all who replied. I will take it out for a test as above at first opportunity and report back. At present we are having some pretty miserable weather so it may have to wait a few days.

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'98 E300 DT
'87 190D 2.5 turbo RIP
'92 S500 Sold
'03 3.2TL-S A-Spec

HA! This may explain it, as I was not aware of it standing in 2nd and then shifting to 1st when I launch. From Park, when I shift to D, I can feel it shift into gear, I press on the pedal and it moves a little bit, then jerks as it engages into gear (or, as you describe it, downshifts to 1st), along with the customary clunk. Any ideas on what might cause this?

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'98 E300 DT
'87 190D 2.5 turbo RIP
'92 S500 Sold
'03 3.2TL-S A-Spec

Thank you, Brian. Here are the numbers: (and I really appreciate the help from everyone)

I disconnected the TRA line and drove around and did not have any flare, but the shifts were harsh (except that the 3-4 shift was smooth). I guess that is a good sign?

I tested the VAC line at the top of the amplifier too, and it was constantly around 40.

Where do I go from here?

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'98 E300 DT
'87 190D 2.5 turbo RIP
'92 S500 Sold
'03 3.2TL-S A-Spec

Bump

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'98 E300 DT
'87 190D 2.5 turbo RIP
'92 S500 Sold
'03 3.2TL-S A-Spec

The first thing we need to do is to reconcile your data. Since a perfect vacuum is 29" and typically max vacuum on a M/B is about 20" and the vacuum to the trans is typically about 11" at idle, your data is in some other units. However, the data does appear to be somewhat correct at the various pedal positions.

If the vehicle has no flare and has no banging of shifts with all the vacuum lines connected, then the amplifier is working correctly.

I'm away for the week and have limited internet access, so, I might not respond for a few days.

Sorry, I was using the cmHg scale on the vacuum gauge. Here are the numbers from the inHg scale:


Idle About 16

Moderate power (about 1/2 pedal) About 12

Heavy power (about 3/4 pedal) about 5

Maximum power under full boost. about 1

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'98 E300 DT
'87 190D 2.5 turbo RIP
'92 S500 Sold
'03 3.2TL-S A-Spec

Those figures confirm that the vacuum amplifier is working properly. The only figures that I'm a bit concerned about are the 16" idle reading and the 12" moderate power reading. Does the vehicle have any soft or mushy shifts that you are not pleased with?

I have successfully shoved the vacuum at idle to slightly below 10" on these to give a very firm shift under most conditions other than very light pedal. I like it that way.