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Listees: Since we were getting a variety of opinions on the GL-4 vs GL-5 debate, I emailed Bob Hoover. Here is his response: > Dear Jim, et al > > Volkswagen used to use BRONZE syncho rings. Bronze is an alloy of copper and > TIN. > > In one of their many 'improvements' Volkswagen went to a cheaper BRASS > synchro ring. Brass is an alloy of copper and ZINC. > > Unfortunately, in trying to save a penny or so per synchro, VW decided to use an > alloy of brass that contained a significant percentage of aluminum. > > Then along came GL-5 tranny lube, which contained a new anti-oxidant, > supposed to allow you to extend the replacement period of the oil, which was > fine for differentials and steel gears and even for the older BRONZE synchros > but pure hell on those new, improved, save-a-penny aluminum-copper-zinc > synchros. > > Bottom line: GL-5 caused the newer synchros to 'honey-comb.' I don't > recall the half-page explanation but GL-5 attacked the zinc in the synchros and > they would break. So VW issued a Service Bulletin telling all of their dealers > to NOT use GL5 on transmissions manufactured after a given date (about 1967, as > I recall... which I don't, all that clearly). > > So use GL-4. Or make sure your tranny is rebuilt using the old style BRONZE > sychros. > > I've never paid much attention to this problem because I've still got most of a > 37 gal drum of GL-4 tranny lube, plus a box full of old synchro rings. > (Replacement of the synchros is a relatively minor chore, compared to replacing > a gear set.) > > You'll have to answer the synthentic lubricant question yourself. When I run > out of tranny lube eight or ten years from now, I might look into the use of > synthetics but having no need to do so, it is a non-issue to me. Sorry I can't > be of more help. > > -Bob Hoover - Jim Adney jadney@vwtype3.org Madison, WI 53711-3054 USA ------------------------------------------------------------------- Search old messages on the Web! Visit http://www.vwtype3.org/list/