Transmission oil

[AliK]

Learned ones,

I was going to buy the Motul gear 300 75w90 fully synth for my newly delivered 3.9 diff and thought it would be good to renew the gearbox oil at the same time.

Would a modern oil be bad for synchros or other parts in the F5W71B gearbox?

Many thanks,
Ali

 

[toopy]

When i looked into this, general consensus was to stick with GL4 definitely for the gearbox and GL5 for the diff.

GL5 can affect the metals in the old transmissions as well as possibly the synchro operation over time.

I bought this for the gearbox https://www.ebay.co.uk/itm/COMMA-SX...011108&hash=item23906c312c:g:IxEAAOSwiDFYNFZX

Some advertised GL4 oil is actually GL5 that is supposedly backwards compatible, read the small print, and again, general consensus was dont risk it!

 

[toopy]

Had a quick google search and the Motul stuff is API GL-4/GL5, so diff yes, gearbox at your own risk !

 

[AliK]

Thanks dude. Great advice!!! [emoji106]

Looking forward to seeing you tomorrow.