Gearbox/Diff oil.......again!!

[johnymd]

I've been looking at drivetrain oils again and still don't know why one is a GL4 and the other GL5. Any ideas. I run a s14 box and the general recommendation is EP85W-140 which is the sort of oil I'd run in a noisy diff. So can i use the same oil in both?

 

[jonbills]

I think the problem used to be that GL5 was capable of handling the high pressures in the diff, but to get it there made it harmful to brass synchros so you wouldn't put it in the gearbox.
Modern oils I think can handle both. I've got this Mannol stuff in both gearbox and diff at the moment. https://www.ebay.co.uk/itm/303156756180

 

[240L31]

I'm running the s13 gearbox and was recommended to use the Redline mt90 oil. It shifts much smoother now, especially when the gearbox is still cold.

Edit: I did back to back testing with several flavors of gl4 oil with the same viscosity - I guess the additives have a major impact on how the gearbox "feels".

 

[ben240z]

Talk to Opie Oils in Cornwall.

 

[atomman]

I've run the Red Line MT90 75w90 Gl-4 stuff in my S14 box since I rebuilt it and it feels lovely .

 

[AliK]

I used the Redline stuff in my gearbox but Alan was recommending Swepco 201 for a gearbox with the steel synchros. That’s what I will use next time as the gearbox feels less smooth than id did before the change to the redline.

For the diff I used Millers GL5.