Trans vacuum modulator
#46
Nordschleife Master
#49
Nordschleife Master
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fonetico, on the modulator ,It really helps to take the bolts out of the heat shield and move it as far out of the way as possible. Also pop off the shift cable making sure not to lose the small wire keeper . I used a socket Allen with a short extension to get the Allen bolts out. I also used an Allen wrench on the most forward bolt because when it is loosened out it runs out of room.
Craig (MainPorsche),I've got everything buttoned up so I'm ready to fine tune the shifting. What do you suggest? Thanks,Doug.
Craig (MainPorsche),I've got everything buttoned up so I'm ready to fine tune the shifting. What do you suggest? Thanks,Doug.
Doug, first thing to adjust is the timing and then you'd go to the strength (pressure modulator adjustment) of the shifts. This is the drill Greg Brown put me through after I installed one of his new transmissions. Timing of shifts is dependent on the tension/levering of the control pressure control cable (Bowden cable) while throttling/stepping on the accelerator pedal. It is easy. You'll need a needle nose plier with a flat bite, a 7 or 8 mm wrench (I forgot what size), and something to pop the cup off the ball at the cable quad for the Bowden cable. I use a carpet tack puller (purchased at Lowes). It is the size of a good sized screw driver but it has a vaulted/angled shaft and the head is like the back end of a hammer to pull out a small nail - it really works well for quickly/cleanly popping the cup off. I included a pic of one which is a straight shafted one.
Anyway, find a quiet piece of road where you can go through different rates of acceleration, and note WHEN the shifts occur. If you think they're a little late and the car 'winds up' to high, pull over safely, pop the cup and tighten the cable by one revolution of the cup (shortening it) - re-attach and test again till you get the timing right. The reverse is true if you're finding the shifts come to early - pop cup and slacken cup/cable - re-attach and test drive again.
Once you have set where good shift change timing is consistent, now ask yourself are the shifts still hard and 'clunky' and do I need to 'adjust' further - This is where modulator adjustment comes in to finalize the matter. Remember you want to correct shifting 'anomaly' by correcting timing as much as possible and modulator adjustment as little as possible. This is where it is time consuming.
After shift timing has been 'set' by drive testing get back to garage and raise the back of the car with jack under center of crossmember and quickly throw in stands under each lift point and put in a stop at the front wheel - I say to do this because you will be doing multiple times while drive testing you pressure adjustments. Remove the black modulator cap and withdraw the 'T' slightly and go one notch at a time CCW and replace cap and test drive again. Some will come here and say one complete revolution till there, but I think doing the one notch at a time adjustment till smooth is more likely to get to your endpoint of smooth shifting more precisely without overshooting the minimum pressure drop to get there. I remember the experts speaking of increased band wear with excesses in modulator pressure lowering. That is why I recommend the painstaking one notch at a time approach.
#53
Nordschleife Master
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That is indeed a job. Do the oil pan gasket while there - you'll have everything cleared to drop the pan and re-gasket. Here's Dwayne's page. I've done most of my stuff solo via his write ups.
http://dwaynesgarage.norcal928.org
http://dwaynesgarage.norcal928.org
#54
Nordschleife Master
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Also, as the steering rack is down you may want to put in Delrin bushings for the rack. Call Roger.
https://rennlist.com/forums/928-foru...elrin+bushings
https://rennlist.com/forums/928-foru...elrin+bushings