Red Line Diff oil GL5

[CharlieB]

Emailed Red Line about synthetic oil for my diff, thought others might be interested in their reply:

"The Red Line MT90 will be perfect in your transmission but not for the rear differential.

Our transmission fluids are blended for the balanced friction required in a manual gearbox but differentials need different properties from the oil. Transmission oil in the diff will wear out the components twice as fast because the oil cannot cope with the extreme pressure and friction within the diff. This is the reason that Red Line blends different gear oils for different applications ( 17 in all ).

For the rear differential you need Red Line 75W90...this is specifically designed for the diff containing both extreme pressure additives and friction modifiers to help the diff work correctly- this fluid would be too slick for the transmission.

Our 75W90 gear oil is a GL-5 grade oil...however
The extreme pressure chemistry used in many other gear oils can be corrosive to brass and bronze used in bushings etc. Most gear oils become highly corrosive by the time they reach 200F. All Red Line gear oils are non-corrosive at 300F and some up to 375F so this should not be a problem."

So I guess some GL5 oils are ok

[Deleted User]

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[Mj17]

lordleonusa wrote:

And, btw, where else would our rear wheel drive differentials be than at the rear?L

In the specific case of a Triumph 2000 it's not necessary, but these people don't just deal with Triumph 2000s so will be in the habit of specifying front/mid/rear differential to ensure their advice/comments are clear an unambiguous.

Personally I'd rather have a clear answer than be left wondering if we were both talking about the same thing.

[CharlieB]

lordleonusa wrote:

And, btw, where else would our rear wheel drive differentials be than at the rear?

Why do people continue to refer to rear differentials and front bonnets etc?

I think he means rear differential as opposed to front differential in a front wheel drive car which typically shares its oil with the gearbox & therefore often uses a different spec oil.

I don't claim to know much about oil, I asked Red Line as they seem to have a good reputation & I thought synthetic might be a good idea in the diff as it will probably not be changed for years.

[Spitfire2500]

I was checking this out recently as well. The tech data on Red Line's web site about their GL5 75W90 is fairly clear about it being safe for units using phosphor/bronze parts so it should be OK.

[Deleted User]

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