928 S4 automatic shifts bad
Thread Starter
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Joined: Dec 2008
Posts: 11
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928 S4 automatic shifts bad
Hi,
I bought a 928 S4 from 1989. When the car shifts it doesn't shift smouthly. I heard that I should adjust some cables. I adjusted the two cables by the engine and adjusted the lever select cable. That all didn't work.
I read the manual and they are talking about "strong jolts when changing gears" I think that that is my problem. Then they write adjusting the pressure but meassure it first. I don't know how too measure. Somebody knows a trick? Ore is it an other problem?
Regards,
I bought a 928 S4 from 1989. When the car shifts it doesn't shift smouthly. I heard that I should adjust some cables. I adjusted the two cables by the engine and adjusted the lever select cable. That all didn't work.
I read the manual and they are talking about "strong jolts when changing gears" I think that that is my problem. Then they write adjusting the pressure but meassure it first. I don't know how too measure. Somebody knows a trick? Ore is it an other problem?
Regards,
Rennlist Member
Joined: Feb 2008
Posts: 2,742
Likes: 0
From: Lillington, NC
They want you to measure the vacuum at the transmission. Adjusting the vacuum actuator on the transmission softens or firms up the shifts. There a few guys in here that really know the auto trans, I'm sure they will chime in with more detail.
Team Owner
Joined: May 2004
Posts: 31,279
Likes: 4,248
From: Philly PA
to measure the shifting pressure you will have to connect pressure hoses to the fluid connections on the trans, a good Mercedes trans rebuilder may have the gauges to do this.
The adjustments are made under the vacuum modulator cap remove the black cap and a small T handle will then pull out of the modulator, CCW reduces the shifting pressure CW increases it.
Dont turn the handle more than a few turns and write down your progress so it can be returned to where you started. IIRC each turn is about 5 PSI of fluid pressure (check the WSM for accurate info)
The adjustments are made under the vacuum modulator cap remove the black cap and a small T handle will then pull out of the modulator, CCW reduces the shifting pressure CW increases it.
Dont turn the handle more than a few turns and write down your progress so it can be returned to where you started. IIRC each turn is about 5 PSI of fluid pressure (check the WSM for accurate info)
Race Director
Joined: Oct 2005
Posts: 11,023
Likes: 72
From: Southern Utah
first thing, give it a visual inspection and see if the vacc line is connected. then pull the line off and see if you have vaccume at the line... then go beg for tools and play with the thumb screw.
