marlinspike

I noticed when looking at the Porsche 928 auto trans vacuum modulator it looks different than the MB part. Anybody know if it is functionally any different?

Also, what would be the symptom of that o-ring on the vac modulator if it wasn't making a perfect seal?

I ask because I have a souped up MB (also uses that same 722.3 trans, just not as a transaxle) and I recently had to replace the trans modulator (went to adjust it to make it slightly firmer, but the rubber cap and the pin were gone). MB has subbed out to a new part (I don't just mean the new sub they did several years ago, but now an even newer sub). With this new one in I can make my shifts firm how I like them, but they're late on full throttle (and no, it's not a bowden cable adjustment issue), late enough that on the 2-3 it will hit the fuel pump cut off before ****ting. MB has had some issues lately subbing in new part numbers with the new parts working, but not quite (or in the case of some hardware not working at all), so I got to looking up the 928 part.

Jascd

I can't help really, but the very late shift does not sound like its the modulator. Does it still shift like that with the bowden disconnected?

marlinspike

Well, I haven't tried disconnecting the bowden cable, but I did try putting so much slack into it that it won't even go into second from a roll unless I'm going slowly, and once in second it holds it until late.....
However, I was messing around with it last night and now I'm not so sure if it's running into the fuel pump cut off, I think it just may be a very very firm shift. It seems like there is a region where adjustments to the modulator get very aggressive, so maybe I just need to fine tune it.

I'd still be interested to know the differences between the 928 modulator and the MB one though.