Gearbox oil change with plated diff

[Rhys1983]

Hi,
I’m looking to change the gearbox oil in my car. It currently runs Castrol Transmax FE75w.
I’ve been reading through the forums and can see that a lot on here recommend ravenol mtf-2 75w80. Is there any benefits to changing to a slightly thicker 75w80 oil from the standard 75w?
Also my car runs a gripper plated diff. The oils recommended for these tend to be GL5 but I’ve heard that these oils are too slick and can damage the synchros and cause poor shifting.
I spoke to Gripper and they said that their diffs tolerate a lot of different oils and to go with the car’s recommendation.
For those of you running plated diffs, what oil do you use and do you add a friction modifier to your standard oil?

 

[M-Sport fan]

It's not that the GL5 gear oils are too slick themselves (but they can be a bit too viscous in the 75W-90 and above weights in colder climes during winter season).

It's the fact that any friction modifiers they might contain (IF they are labeled as an 'LS' limited slip additive already in the formulation) could cause the synchros to not engage properly, hence the poor shifting.

If Gripper claims that their plated clutch type diff can fully function just fine without said limited slip friction modifiers, I would just go with the Ravenol MTF-2 or equivalent.
Did you speak to an actual tech there, or just a salesman who picks up the phone or answers emails??

Of course, the sequential transaxles in the Rally 3, 4 and now even 5 cars do not have to worry about synchro function at all, and can use said friction modifiers for their ramped, plated clutch type diffs.

 

[Rhys1983]

Thanks @M-Sport fan.
I’ve also had confirmation from gripper from a technician that people run their diffs with all sorts of weird and wonderful oils without any problems. They just recommend that the oil gets changed every 6 months which isn’t a problem as I tend to get an engine oil change every 6 months so will get both done at the same time.
I’ll try the Ravenol MTF-2 oil next time as it gets really good reviews. 👍