915 Synchro Ring Orientation

[Jim Sims]

Starting to reassemble synchro's in a '73 5-speed 915. Factory shop manual states to put rough side of new synchro ring towards operating sleeve (slider). Both axial faces of new synchro rings appear to have an equivalent machined finish; one face has the very small letters "GOE" (Goetze, the manufacturer?) etched near the gap but otherwise no difference. The radial profiles of the rings are coated with a friction compound. Are the factory orientation instructions obsolete or are we missing something about the surface finish? Thanks! Jim

[ChrisBennet]

No difference as far as I know. If you're trying to save some bucks and not replace the syncro you can flip them to expose the less warn side.
-Chris

[Jim Sims]

Thanks Chris. We're replacing all the synchro rings, all the brake bands, 1/2 and 3/4 operating sleeves, 1st and 2nd synchro hubs (dogteeth - I believe I've found a NOS symmetrical 1st synchro hub) plus all the thrust washers (edge cracks!), dentents and of course all new seals. We want to retain the original setup as there is a shifting advantage to it (according to PCA) over the asymmetrical upgrade. Yesterday we bought a piece of plastic rod to make the tool to hold the 5th gear detent in place while the outer roll pin is driven in and a selection of plastic and copper pipe fittings (1" and 1-1/4") to use to make the thrust blocks to push everything back together in the shop press during reassembly of the shafts. Cheers, Jim

[john walker's workshop]

you don't have a choice on 1st gear about using the asymmetrical setup, as the symmetrical parts are obsolete. the new shift sleeve will be asymmetrical, so you cannot use the NOS symmetrical teeth you found. you would have to use a used sleeve. brake bands and stop dogs are updated too, for 1st and 2nd, as you know. the press is only needed to push on the syncro teeth. the few things on the shafts that offer slight resistance can be installed with a hammer and drift.

[Jim Sims]

John, Much to my surprise the old symmetrical 1/2 shift sleeves (915.302.411.00) and brake bands for 1st and 2nd (915.302.316.01) are available new out of the Porsche parts system. A few days ago we received the parts and they are identical to the 1973 pieces (except for the wear of course). The sliding sleeve doesn't have the asymmetrical teeth of the new design but the symmetrical teeth of the original design. The parts system didn't produce the symmetrical 1st gear dogteeth; we had to locate that NOS. We were expecting to have to do the upgrade (the advantage we're told of the upgrade is its easier to shift into 1st at the cost of slower shifting into 2nd) but sent in various options to the part system including just rebuilding with old style parts (our first preference). The parts system produced the old style parts so that's what we're using. I think the only item not available through the part system is the old style symmetrical first gear dog teeth but I'm not even sure of that fact. Cheers, Jim

[john walker's workshop]

wow, those pieces have been unavailable for years. too bad about the 1st teeth though.