namasgt

A few months ago I was talking to a Mercedes mechanic. He advised to never blindly adjust the modulator, when the car is shifting hard. Look into adjusting the bow-den cable or to see if you have enough fluid. Because when you adjust the modulator to make it shift softer it causes the clutch plates to wear prematurely. He also said once you turn it and then turn it back to were it was you may not end up with the original setting, you have to either re adjust per the manual or buy a new one, which he made it sound like they come pre adjusted out of the box???

GregBBRD

You need to put a set of gauges onto the transmission to adjust the modulator. Then you need to drive it and fine tune it, if required. The kickdown cable needs to be properly adjusted, before you do this.

namasgt

^^^^ Well some people adjust it without the gauges. They adjust them until the shifting feels soft.... But does a new one out of the box need adjusting too or is it pre adjusted. He said they come in different colors like ours is Green, but you can also get Red? that has a different setting, or causes a different shifting characteristics.

ammonman

Per the Porsche Troubleshooting guide for the A28 series of transmissions (WKD 490 620), no movement forward or reverse regardless of shift lever position has the following causes (most of which you have eliminated.):
1. Low fluid level. Missing or faulty filler neck seal.
2. ATF is burnt (stinks and is black instead of red/brown)
3. Severed connection between engine and transmission
4. Selector lever cable mis-adjusted
5. ATF filter plugged
6. Fault in valve body
7. Primary pump damaged

With the failure mode you describe my money is on the valve body. You might drain off enough fluid to allow the addition of some Trans-X cleaner. IF the issue is in the valve body and is a stuck or dirty valve the Trans-X might free it up and allow the body to start functioning again. Short of that I fear you are in need of a large clean workbench and a bunch of bins to put parts in and label or a plastic box and shipping instructions to Dr. Brown.

Best of luck

Mike

MainePorsche

I adjusted the modulator as prescribed with a few short turns of the key, BUT did not use gauges. At the time I was not knowledgable of addressing the hard shift issue via the bowden cable. I find I am learning a lot on RL, though sometimes not so timely.
Would be interesting to confirm if the modulators come pre-set, and if ordering a color coded one could tailor to one's needs regarding timing of the shifts.

Mike, Thanks for this input.
In my scenario, only item 6 (fault in the valve body) stands alone as unchecked/unknown. Knowing my mantra of doing all I can till my abilities are exhausted, the valve body cleaning idea you speak of might tempt me. I have not looked locally yet for 'Trans-X' cleaner, but is it a specific type of cleaner and/or are there other suitable substitutes, if 'Trans-X' unavailable here ?
Even if I were to do this, I think once the season rolls in, and the car is winterized, and un-driven, I'll be sending a parcel to Greg.
Craig

Charley B

Boy, this sure answers a lot of questions and verifies a lot of suspicions that I have dealt with over the years in my naive struggles with transmissions. I've suspected this was the case but never had the confidence and the ***** to buy a manual and start tearing apart an offending transmission.

ammonman

If you can't find Trans-X look for a product that is primarily a sludge and varnish remover instead of more directed toward stopping leaks. Trans-X advertises both while the SeaFoam product called "TransTune" is only a sludge, varnish, and moisture remover. Trans-X is made by CRC Corp. Either company's web site will direct you to a local vendor.

Mike

Bertrand Daoust

Here's a site for some info on our trans including some on ajusting the modulator.
Hope this will help.

http://www.benzworld.org/forums/w201...l-replace.html

Bertrand Daoust

This looks interesting too.

http://avtopedia.ru/akpp/722-3%20722-4.pdf

MainePorsche

Mike,
Thank you for your time, and information.
Craig

MainePorsche

Bertrand,
Thanks. Will be helpful when I have to remove the valve body to send to Greg. Adjusting the modulator is now not an issue, but the adjustment procedure may be helpful later.
Craig

Leon Speed

Maybe I missed it, but can it be that the linkage is loose on the input shaft?

MainePorsche

Leon,
Hardware all intact and functional at the selector arm input shaft.

MainePorsche

Well Guys,
The saga continues. Replaced the non vacuum holding modulator with a new one. Checked to see if vacuum held form the lines origin at the 'T' -> it did not hold any vacuum which told me the line was faulted. I have about 20 in Hg at the 'T'. Temporarily ran a one piece line from the 'T' to the modulator.
The wheels turn slightly in D and R then stop. With throttle they move only a bit, and not as expected.
I removed some ATF and added SeaFoam Trans Tune in an attempt to loosen up any thing tying up a valve.
A question for you, being that I can't drive it, am I able to warm the ATF up enough in idle to then get an accurate fill level ? If so, how long of an idle would you estimate ?
I want to try to do what I can before having to remove the valve body to send it to Greg.

MainePorsche

Now another interesting finding.
When it is in R at idle no rotation of wheels -> when I give it some throttle the WHEELS TURN AS IF IT IS IN DRIVE !