Motul Gear Competition 75W-140 in Transmission and Diff
 

EDIT: Mods I realized I posted this in the wrong forum, I have now posted it in the maintenance sub forum. Feel free to delete if desired.

Hey guys,

About a month and a half ago I went to a local performance shop to swap out the factory fill of trans and diff fluid for something a bit better (at about 18k kms).

I know that many in the community use Motul Gear 300, so when my mechanic recommended Gear Competition I really didn't think twice about it. He said its his go to recommendation for Subaru's (WRX's, STI's BRZ's and FRSes) and has used it many times in the past so I trusted his word.

Now upon doing more research about it, I am getting worried that I may be doing harm to my trans/diff. Should I flush and fill with a 75W-90?

Fine in both, but you may find reduced mpg and increased notchiness shifting.

On cold temps right? Because on warm or driven for a while shifting improve dramatically

Ultimately it's not what's recommended by the manufacturer. I don't believe it will hurt the car *short term*

Your car, your risk.

Motul Gear Competition 75W-140 in Transmission and Diff
 

Noted. I may keep this fill then until my next interval and switch to Gear 300 after that. I haven’t noticed anything out of the ordinary; it is notchier than the stock fluid in the cold (below 5 deg C) when nothing has warmed up, but I double clutch on upshifts and downshifts when the car is cold anyways.

Otherwise the shifter feels better than the stock fluid once up to temp.

As an aside, I know second gear can be “crunchy” in this car from time to time, but I also get the odd bit of synchro noise when shifting to third as well (fairly rarely, maybe once on a 45 min commute). I had this issue with the stock fluid as well. Does anyone else have this issue?

Yes, sometimes ...... if I get "lazy leg" ...... don't push the clutch pedal all the way to the floor ...... :sigh:


humfrz

Fair enough! I may be doing the same without realizing it... :lol: