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Sun Aug 17, 2008 7:31 pm

Glenn wrote: So they you're suggesting taking a new transmission, filling it with GL5 and then letting it sit for 15 years?

VW listed GL4 because in 1972 GL5 wasn't available yet.

So... where do you get 91RON leaded gas these days?

I was thinking of one using a gear/trans oil quite the opposite of what is called for (spec wise) in 'whatever said vehicle'. Nothing mentioned about setting for any amount of time.

Leaded gas...here in the states :shock:

"The truth is out there...somewhere

Sat Aug 30, 2008 7:45 pm

http://static.summitracing.com/global/images/instructions/red-synthetic%20gear%20oils.pdf
note: CORROSION PROTECTION
The extreme pressure chemistry used in many gear oils
can be corrosive to brass and bronze used in synchronizers
and bushings. Most gear oils are corrosive at
temperatures of 200°F. Red Line Gear Oils are non-corrosive
up to 300°F and the MTL® in excess of 375°F. A
corrosive gear oil can shorten synchronizer life by half
and can also contribute to rust problems.
I went with the 75W90 NS. Which is GL-5. I considered the extreme pressure formulas and MT-90. But I was put onto the NS by an article describing regular GL-5 as mostly for differentials and not working as well for gear synchronizers. The NS was recomended as working well in Porsche transaxles among others. I got tired of researching it all and put in the GL-5 NS. BTW I didn't get a full drain because of the axles so it's mixed with regular GL-5. The only difference I can tell is from when it had the old 90w dino oil and I replaced it with regular GL-5. It is much smoother when cold.
The MT90 is a GL-4 and is what I would use if I thought it had to be GL-4. But the only thing I've proved to myself is that synthetic beats dino.

Sat Aug 30, 2008 8:56 pm

Beware, you've changed TWO things at once. Either of them could be responsible for the improved shifting. You changed from regular oil to synthetic, and you have changed the viscosity of the oil. Which of those 2 factors caused the improvement in shifting?

Oh, and if anyone who read the fine print thinks their synchros will corrode away, your gear oil NEVER gets even remotely close to 200ºF.

Sun Aug 31, 2008 6:01 am

Yeah the change to synthetic is secondary to weight most likely but then again because it's synthetic I can change weight.
Check out the Shockproof EPs for instance. And if you want GL-4 there is MT90.