Question on syncro repairs

[brushhippie]

I had the tranny start squalling really bad in every gear but 5th and reverse...it did this soon after I bought it so I replaced both engine and tranny with a donor...which is losing oil fairly quickly..2 quarts a week...I do not believe it leaks sitting still..I think it pushes it out while driving...I am anxious to see if putting heavier oil in it does not help...I am going to try the 20/50 mc oil..thanks for sharing that.

[ryanprins13]

Yeah, I like that Valvoline 20/50. I used to get a lot of brass shavings with my trans fluid changes on Tweak, after I switched to that it stayed clean and I even reused it after it was in the car a whole season! I was dumping the ATF between race days, and getting shavings. Gear oil shifted hard when I was trying to shift fast. The 20/50 is a good balance. Motorcycle oil is designed to promote some friction because motorcycles have wet clutches. The syncros are sort of little wet clutches, so they need a little friction to work properly. That was my thoery and it seems to work.

I have always used atf or 10w30 but am going to switch for the 3 months of towing i will do. Have you tried anything else? Like redline, amsoil or honda mtf, syncromesh... Anything like that?

[Icedawg]

I'm using racing motorcycle 20W50, just because Charlie does. Never had an issue. Also, as a bonus, it's too thick to leak out the driveshaft seals!

I think the 75W80 is much too thick. Sounds like rear diff oil.
.

Gear oil spec units are quite different than engine oil. The 20/50 motorcycle engine oil is much thicker than a 75/80 gear oil.
Redline compares their gear oils to engine oils and their 75W80 MTL is a 5W30 engine oil viscosity comparison, while 75W90 gear oil is compared to 15W40 engine oil.
So the 20w50 engine oil advance is using is heavier than most gear oil choices. It could be a very good choice for racing, and his synchro wear he sees suggests that, but it may be too thick for street driving.
I race with Redline MTL in winter and MT-90 in summer.