I built a 1600 GB with Paul's synchro rings and OSG gearset. I also replaced the input shaft bearing and several other's as well as I consider them time change items regardless of how they look. Admittedly it's a street car "BUT" it does get driven as hard as I can drive it. I used Paul's Sychro ring prep instructions as well as his very detailed assembly instructions with photos (nice job Paul). Filled the box with 75-140 synthetic oil and ran it for about 1000 miles. Drained it to check the magnet on the plug. No metal shavings at all.. Wasn't completely happy with the shift "feel" (shift transitions) so I went back to 85-140 standard Lucas gear oil. Shift "feel" improved dramtically and engagement is seamless. I realize that gear oil is somewhat subjective other than hard data Richard and other's have put forth in this thread so I have to also attach the disclaimer that: "these are my personal observations and should be taken as such."SYNCRO RING PROBLEMS
We were an Alfa shop before becoming a dealer. As Paul Spruell Alfa we sold some 5000 new and used Alfas. We had MANY gearbox warranty claims. New and rebuilt gear boxes were stiff and balky for a long period of time. The texture of the sintered material on the replacement syncro rings was extremely coarse. When gearlube was changed after the 500 mile interval the magnetic plug would have a long beard of ferrous filings from the syncros.
For years in the Alfa repair business, I had scavenged good used syncros in the shop and reused them in my race gearboxes with great success. So, why not do a few strokes with some 100 grit sand paper and smooth off the new syncros? Our service department gave it a try and it was snick-snick from the get go. By artificially breaking in new syncros the gearboxes lived happily ever after. Without the extreme coarseness syncro life was remarkably improved.
Spruell Motorsport currently sells several hundred reproduction syncro rings each year. With all syncro sales we furnish GB rebuild instructions that include our syncro modification procedure. There has been no negative feed back. We furnish free syncros with OS Giken gearsets and there has been ZERO syncro failures in some 30 sets. Then last week a customer’s new GB blew up really big time. A world renowned race parts vendor talked him into using genuine Alfa syncros with the little yellow stripe instead of our proven quality reproductions that came with the gearset. The builder also ignored the instructions we furnished. It was stiff as hell through the gears and after five laps the 4th syncro pealed off totaling the gearset and exploding the case. The twin plate race clutch probably contributed.
One would think that our syncro modification procedure would have made it around the globe by now. For decades our shop successfully used modified yellow striped syncros. From what we are hearing, the current “Alfa” manufacture may indeed be defective. These failures are likely due to some combination of surface texture, different ferrous coating and not enough strength/spring in the ring. With that said, this Alfa parts vendor recommends that you scrap your yellow stripers and order some of our reasonably priced reproductions…..and, of course follow instructions.
I would like to get some intial thoughts as to OSG's integration of Nissan synchro sub assemblies with alfa gear sets? I suspect OSG has a great deal of history with Nissan GB's and came to the conclusion after reading the alfa bb for an extended period of time that enough was enough.