PeachParts Mercedes-Benz Forum - View Single Post

EricSilver · #11 04-05-2007, 05:27 PM

I am experiencing minor flare between 2nd and 3rd gear upshifts. Tech looked at car, and I believe he checked/tested vacuum at the SOV. Diagnosis was:

"Shift Point Cable" leak in vacuum element on the transmission.
Cost of repair: $1,200 parts and labor

I declined the repair because it is a non-critical issue. The Tech capped off the vacuum line to the tranny, to stop the vacuum leak, and installed a new shifter bushing (at my request). Net cost: $51.00

Presently, shifting is near-normal, with a minor 2-3 flare. To confirm the vacuum leak diagnosis, I checked the DM for a code 26, but got only my ever-present Code 5 (because I have an EGR tube to clean). I did, however, see a code 26 back in November, which never returned after I cleared it. Questions:

1. Is the above diagnosis by the tech reliable? Can the leaky vacuum element, alone, be replaced, versus the entire "Shift Point Cable?"

2. Before even considering replacing the vacuum element, would it not be wise to first test the vacuum line from between the SOV and the trans element, since that is what could be actually leaking?

3. With no vacuum to the transmission element, will my 2-3 upshift delay/flare persist?

4. Can tweaking the throttle cable, Bowden cable, and Vacuum modulator compensate for, or eliminate, the upshift delay?

So far, I have experimented with the Throttle cable, mistakenly thinking it was the Bowden cable. Tightening it did speed up the timing of the shifts, helping to mask the flare. But it also made me go faster than I should with normal accelerator peddle pressure, so I restored it (almost) back to its original position.

Other than that, I have located what I believe to be the Bowden cable (see photo); and identified the vacuum modulator on the trans. (I have the newer-style white plastic cap.)

Thanks for any advice.