Synchro Question

[turboteener]

I heard a VW guy talking about removing every other tooth from the 2nd gear synchro hub to improve shifting. Has anyone ever done this with a Porsche tranny? Obviously it could weaken the synchro hub but it would also improve shifting as it would allow less precise engagement requirements.

[John Rogers]

I asked a couple of people more knowlegable than I am with these transmisions and they had not tried it and said they weren't sure it would make any difference? I wouldn't try it since the 1st to 2nd shift on a 901 transmission is not meant to be made like a "speed shift" anyways, just smooth and precise. Why not try it and make an article about it if it works? Good luck

[Dave at Pelican Parts]

Brett just got a reply on the Rennlist 914 e-mail list. This is from Paul Guard, at Guard Transmissions, who is the transmission guru for 901 and 915 gearboxes.

The process actually involves the grinding off of every other of the small engagement teeth, NOT the brass synchro teeth. The real trick is doing the same on the matching teeth of the slider, as without doing this, there is no difference in performance whatsoever. Over the years, this mod has come to be called the "slick-shift" modification, and allows the removal of the brass synchros and other associated bits altogether (although you would want to retain these in a street car). There are some pitfalls to avoid, relating to the varying tooth geometry in the different production years.

I may have been the only fool to waste his time trying this in the 901, as well. Unfortunately, the number of teeth in the 901 requires that 2 of every 3 teeth be removed, rather than every other tooth. While thisremoval of 2 of every 3 teeth works well in a VW, the 901 teeth areentirely too small and are not strong enough. They will break after perhaps 3 quarter-mile passes. (And the modification of the slider is perhaps the most time-consuming/wasting experiment I have performed to the 901.)

Which VW chat group, Brett?

Paul

--DD