Best gear box lube?

http://www.lastgreatroadtrip.com/wp-con ... arison.pdf

A Study of Automotive Gear Lubes 20
Conclusion
As the testing indicates, AMSOIL Severe Gear ranked highest among all gear lubes tested. It was the only gear lube to
score a 4 or better in all performance categories. The high ranking of AMSOIL Severe Gear clearly points to a well-balanced
formulation capable of delivering effective, long-lasting lubrication protection to all differential components. Most notable is
the superior performance of AMSOIL Severe Gear in the critical areas of extreme-pressure protection and viscosity and
oxidation stability. Based on the performance testing, the slightly higher than average price of AMSOIL Severe Gear would
be offset by the cost savings achieved through reduced maintenance, longer lasting differentials and extended lubricant life

This is GL-5 isn't it? I was under the impression that GL-5 would degrade bronze bushings in the Commando gearbox and other vintage MC gearboxes and should be avoided in favor of oil with a GL-4 rating. I am not familiar with the MT-1 rating. I have been using Redline MTL 75W80 GL-4 Gear Oil gear oil in my Commando the last change because I inherited a bottle of the stuff. Before that, I was using an 85W90 GL-4 gear oil made by Sta-lube from the local automotive parts store. I run this latter stuff in all my vintage bikes.

Don't think gear lubes for last few decades have bronze eating elements but will check with manufactures for AMC's but no bronze bushes in TTI only needle bearings they assured me.

This is the oil Amsoil recommends for manual transmissions. It is: Manual Transmission & Transaxle Gear Lube 75W-90. I put Severe Gear in mine and suddenly got a whole bunch of brass -yikes- but it was not the degrading of brass that did it but the slickness of the lube that let the bushing in first gear slide over and start eating on the bushing in the kick start quadrant.

There is yet an ongoing discussion of the difference between GL4 and GL5 gear lubes on the internet. A lot of synthetic manufacturers are saying that their GL5s don't degrade yellow metals. I think it is Mobile 1 that has a disclaimer and won't whole heartedly recommend their GL5 for syncromesh transmissions (Which are the ones most affected by the yellow metal degradation.)
Dan.

Now that's just plain funny Dan, that lubes have now exceeded the AMC friction dependent design. Double funny i've seen same thing a couple times before I got safer on THE Gunk to not stay in 1st very much. At least the lube didn't dissolve the bush. Gear box break in lube should be cheapest as should be dumped pretty soon after a bush renewals.

This is GL-5 isn't it? I was under the impression that GL-5 would degrade bronze bushings in the Commando gearbox and other vintage MC gearboxes and should be avoided in favor of oil with a GL-4 rating.

Click to expand...

Back in the day when the GL-5 was introduced that was true, but they changed the additives years ago and its no longer true, even if you got some 20 year old stock the chemical attack needed the oil to be above 100C which in our pre unit engines is never going to happen, instead we have to suffer from milky oil form condensation as the oil never gets hot enough to drive the water out.

I recently pulled the gear box apart on my MKIII to check on the notorious lay shaft bearing. 60,000 miles and it had never been apart. It's had Mobil 1 or Motul 75/90 gear oil in it for the past 20 years.

Everything looked pretty good including the notorious lay shaft bearing. All bushings were in very nice shape. 2nd and 4th gear sets showed some wear but not enough to replace them. I replaced all the bearings and the sleeve gear bushings.

Hopefully it will go another 60K without issue.

Ken

Personally I prefer Dexton type ATF when the going gets tough on AMC bushes in lower gears.

Wal-Mart markets a quality gear lube, here's a picture I took today, customer handed me the jug to fill the rotary axis worm gear drive I'd just reassembled on a quarter million dollar horizontal milling center. :shock: :roll: