Shark Attack

Some one educate me a bit on this topic.
How does a syncro work?
Did the early years go bad on the 1-2 up shift or the 2-1 down shift or are they the same thing/part?

Daniel Dudley

An analogy; when you are driving and you engage the clutch, the engine will speed up or slow down to match the speed the car is going. If the engine wants to be at 3000 rpm at 30 mph, letting the cluch engage will cause it to be so. Syncros are like friction clutches that speed up the gears to match the driveshaft speed.. You push the shift lever, and the syncros engage to match gears to the speed that the shaft is spinning and as you finish moving the lever the gears engage with the shaft.Worn syncros are like a worn clutch. They slip, and cannot bring the gears to a matching speed with the shaft. When this happens, either you hear a slight grinding noise and the gears engage, or you hear a great grinding noise and they don't. Obviously, you can help the syncros by matching engine revs and double clutching, but the syncros still take up the slack as it were.

Early porsche syncros use a texture on the clutch surfaces to provide friction. as the texture wears off, the friction is reduced. Later borg warner type syncros have big teeth for bite that are much harder to wear off. BTW, the same syncros are used for up and downshifts between the same gearsets. First second up and down, second third up and down, Third forth and etcetera.

That is the readers digest version. Should give you the idea. First second syncros work the hardest, and are usually the first set to go. Hope this helps.

hacker-pschorr

Brand new early style syncros have been known to grind - horrible design.

Hey Carl - all the cool stuff you design for the early cars, how about coming up with a good set of 1-2 syncros for the pre 84 trannies? Figure this out the S4 guys will love you since it will make finding a 2:73 trannie easier (with good syncros)

Jim bailey - 928 International

Correct when you move the shift lever gear sets which are moving at different speeds must mesh and the syncronizer is what helps do this and is what wears over time from use and abuse. The noise you hear when they are worn is not the syncro but the gears and sliders in the transmission machining bits of metal off each other. So in the typical rebuild it needs at least syncros and sliders and engaging (dog teeth) to restore it to proper function. All of which brings me to recommend that you slow down the car with the brakes and not by downshifting since brakes are much cheaper and more efficient than transmissions and clutches. Up shifts should be made deliberately but not terribly quickly.

hacker-pschorr

Screw that Jim - Grind-em till it fits!

Shark Attack

thanks, I get it. now who do i get to do the work? does it have to be a Porsche guy or can it be a joe shmoe tranny guy? whatta the parts cost? I rebuilt my tr8 tranny when i was 17, is this tranny much different? shoudl i leave it to a pro?

Jim bailey - 928 International

A number of owners have successfully repaired their own 5 speed transmissions. At a minimum it probably will need several hundred dollars of new parts. Some cores sent to us are so far gone they are not rebuildable from a practical standpoint. Click into the store and it lists transmission parts.