Best lube???

[nomad]

Any specific gear oil I should use in my differential? Wondering if I should source GL4 to protect any brass thrust washers or bearing roller spacers or should I be concerned about any extra duty lubes.

Kurt

[h20hamelan]

Maybe redline GL4, likely the amsoil but redline is maybe better. Not Lucas.
The ford motocraft is about the same price, and synthetic, GL4 too. What I use.

[promotor]

Any specific gear oil I should use in my differential? Wondering if I should source GL4 to protect any brass thrust washers or bearing roller spacers or should I be concerned about any extra duty lubes.

Kurt

Use at least API GL5 oil in diffs, GL4 isn't as good at dealing with the loads of hypoid gears.

[h20hamelan]

Is the brass in the gearbox of concern, GL5 in N America seems to be a problem on brass?

[promotor]

Is the brass in the gearbox of concern, GL5 in N America seems to be a problem on brass?

Yes, GL4 for brass synchro gearboxes, and GL5 for diffs. Or EP80 for gearboxes and EP90 for diffs if using original spec oils.

(Although not applicable to Lotus Elans, transaxles however, present other oil-selection issues where gearbox gears and differential gears share the same oil - GL5 causes issues with brass rings so GL4 is sometimes used, which compromises Hypoid CWP gears).

[rgh0]

Yes GL5 must be used for Hypoid gears in the Elan diff I use Redline 75W90 gear oil in the diff. The traditional reason Gl5 oils were unfriendly to brass was the high sulphur levels required to achieve GL5 properties which are all about reducing the sliding gear friction found in Hypoid (and worm )gears. Modern full synthetic GL5 oils like the Redline does not require these high Sulphur levels and does not corrode brass which is not present in the diff in any case. You can generally smell the high sulphur levels especially in used non synthetic GL5 diff oil

Many modern transaxles dont use Hypoid gears so they can use a GL4 oil which is typically desirable to achieve the right friction characteristics for synchro rings operation. My Esprit is an example of this.

cheers
Rohan

[promotor]

Yes GL5 must be used for Hypoid gears in the Elan diff I use Redline 75W90 gear oil in the diff. The traditional reason Gl5 oils were unfriendly to brass was the high sulphur levels required to achieve GL5 properties which are all about reducing the sliding gear friction found in Hypoid (and worm )gears. Modern full synthetic GL5 oils like the Redline does not require these high Sulphur levels and does not corrode brass which is not present in the diff in any case. You can generally smell the high sulphur levels especially in used non synthetic GL5 diff oil

Many modern transaxles dont use Hypoid gears so they can use a GL4 oil which is typically desirable to achieve the right friction characteristics for synchro rings operation. My Esprit is an example of this.

cheers
Rohan

Thanks, interesting to know regarding the Esprit transaxle.
An example of a transaxle with hypoid gears is the Corvair where GL4 oil was recommended. 60's technology though so not modern at all!

[nomad]

I'm running Redline MT90 in the gearbox. Have used it in several other gearboxes and the difference it makes in the gearbox is like night and day,
As for the diff I thought that CL5 was mainly formulated for limited slip differentials. Haven't had a Lotus/Ford diff apart to see if there is any brass in it. Will take Rohan's advice on modern GL5.

Thanks
Kurt