80- 90 weight or gl4???

[glbft1]

got a question am running 80 -90 weight in everything should i be running gl-4? everything is diffs all gear boxes overdrive and swivels, read somewhere to run gl-4 because of brass tidbits inside???
thanks

[yorker]

There was a lengthy post on this a little while ago here. Short version: GL5 would be fine everywhere except perhaps the transmission where GL4 may be safer for the synchros.

[jac04]

Look for an oil that meets GL-5 and MT-1. The MT-1 spec means that the EP additives in the oil are non-corrosive to yellow metals.

[yorker]

•API Category GL-4 designates the type of service characteristic of spiral-bevel and hypoid gears in automotive axles operated under moderate speeds and loads. These oils may be used in selected manual transmission and transaxle applications.

•API Category GL-5 designates the type of service characteristic of gears, particularly hypoids in automotive axles under high-speed and/or low-speed, high-torque conditions. Lubricants qualified under U.S. Military specification MIL-L-2105D (formerly MIL-L-2015C), MIL-PRF-2105E and SAE J2360 satisfy the requirements of the API GL-5 service designation.

•API Category MT-1 designates lubricants intended for non-synchronized manual transmissions used in buses and heavy-duty trucks. Lubricants meeting API MT-1 provide protection against the combination of thermal degradation, component wear, and oil seal deterioration which is not provided by lubricants meeting only the requirements of API GL-4 and API GL-5.

[alaskajosh]

What about synthetics? I'm thinking of the Amsoil gear oil that RN sells.. Should they be okay with yellow metals?

Thanks and kind regards, Josh

[glbft1]

don't know if this makes a difference but the trans is syncro only in 3rd and 4th its a late series 2a

[Jim-ME]

I've been using Lucas Heavy Duty 80W-90 Gear Oil which meets API MT-1 standards in my Rover everywhere gear oil is required for over 3 years and have had no issues.
Jim