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I asked Roger to send me what I needed to change the fluid and filter for my transmission. He included a Mercedes bag of springs and plungers, Part # A 126 270 44 77. I've figured out what they are, sorta, and where they go, but my searching has not revealed why I should be installing them. Can anyone satisfy my curiosity?
I found some similar things, but your link and the links it contains are good. Thanks.
I should just ask Roger, but I'm still puzzled about why he sent the kit to me. Apparently, he must think it's worth doing whether you have the 2-3 flair problem or not. (I have the opposite problem: harsh shifting. I'm doing the first step here, doing a service. The vacuum line behind the engine holds vacuum. The next step is to fiddle with the modulator, I believe. Quadrant adjustments ....)
Everything I touch is something I can mess up, so I am reluctant. The drive to Frenzy is at risk!
Preventative maintenance - cheap and well worth doing while you are in there.
You should be good for another 100k miles.
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Thanks, Roger. I just got everything back together, and have my hose and funnel ready.
There are various tips for putting the "bag" items together (some assembly required). I used a woodworking clamp - easy. I did it in the smallest room available - a bathroom, toilet seat down. That would greatly reduce the search pattern for bouncing springs.
I collected about two gallons of fluid from the two drain ports. The fluid was nice and pink, and everything else looked clean as a whistle. But the fluid was pretty stinky. I don't have an experienced nose for vintage fluid - I wouldn't say it smelled burnt. The two gallons includes what I squeezed out of rags and paper towels. I have not yet learned the fine art of spill avoidance. The valve body sure can drip for a long time - days, weeks?
The auto parts guy was curious what kind of car needed so much fluid. I reluctantly admitted it was a [snooty european oddball with a funny name]. 90% of the vehicles around here are pickups and Subarus. The other guy at the counter said "Beautiful car! I had one once." Wasn't expecting that.
I found the modulator! If the new fluid doesn't work the miracle I'm hoping for, which way should I adjust it to make shifting softer?
Vacuum-check the modulator itself with your MitiVac or equivalent to make sure it's not leaking. Then a vacuum gauge T'd into the flex line at the modulator, with engine running, should show the same manifold pressure that you see in the engine bay at a fuel pressure regulator or damper. A disconnected or mis-connected vacuum line to the trans can cause easily the hard shifting. Since most friction systems don't get better with age, my search for a 'why' on the firmer shifting would start well before I started making modulator adjustments. Were it me.
Vacuum-check the modulator itself with your MitiVac or equivalent to make sure it's not leaking. Then a vacuum gauge T'd into the flex line at the modulator, with engine running, should show the same manifold pressure that you see in the engine bay at a fuel pressure regulator or damper. A disconnected or mis-connected vacuum line to the trans can cause easily the hard shifting. Since most friction systems don't get better with age, my search for a 'why' on the firmer shifting would start well before I started making modulator adjustments. Were it me.
I was able to pull a good vacuum on the modulator line from behind the engine. I believe that rules out a break in the line to the modulator, and one failure mode within the modulator. It does not rule out a pinch or blockage in the line (does that ever happen?)
I don't see that there is a vacuum line to the modulator itself - it goes somewhere nearby. Correct?
Obviously, I should be doing more home work. What I've read, however, is a little scary. Including your adventures, Seth!
The new fluid did not affect the shifting, but the car still runs, which always comes as a pleasant surprise.
The vacuum line does (or should...) go to the modulator. Its purpose is to help manage shift "firmness" based on engine load. So higher manifold pressure (indicating a higher engine load) would firm up the shift. Together, the actual difference in shifting should be negligible, with the load vs. firmness offsetting each other in the perception of shift harshness. Chasing a shaft that's "too firm" might start with driving the car with a firm foot and seeing if it shifts too hard even with higher load. If it does, then look at adjusting the modulator. If the shift under hard throttle isn't too harsh, keep looking at vacuum and maybe the modulator itself.
The TV (throttle valve, loosely translated) cable controls the timing of shifts relative to throttle pressure, so has only an indirect effect on shift firmness.
Curt, go to this thread from when I once gave some advisement to a fellow and his hard shifting issues. I went back and found it by Advanced Search under 'control pressure control cable' in posts made by me. A bunch of threads came up that may be helpful.
On second look, I found the vacuum line to the modulator - it has a fabric cover at this point, enough to fool my old eyes. The line does not hold vacuum when disconnected at this point and hooked to the mity-vac, correct behavior.
I impetuously twisted the modulator T-handle a one-slot turn CCW. I think it removed half of the harshness - some actual flair on 1-2, and only "harsh" on 2-3 compared to "bam!". 3-4 has almost become imperceptible.
Another one-slot turn, coming up...
I'll look at that thread later, Fred. I'm going with blissful ignorance for now.
09-13-2016, 10:32 PM
Mystery bag: K1 Accumulator
George Layton March 2014
