daviddunlop83

iTrader: (7)

Im going to be fitting a new clutch to the car shortly and want to change the gearbox and rear diff oil in my 2wd cosworth.

What gear box oil is the best one to use? I have read either dexron 3 ATF or 75/90 fully synthetic gear oil for the gear box but which one is better?

Also what oil is best for the rear diff?

tabetha

Diff oil has to be LSD oil, I use EP90 in diff, and 75W90 gear oil in box.
tabetha

daviddunlop83

iTrader: (7)

Thanks, i see someone people put 75/90 fully synthetic in the diff? Does this make any difference over the LSD EP90 Oil?

Whats the difference in putting the 75/90 over the ATF oil in the gearbox?

Thanks

tabetha

Depending on how old the box is, ie whether it has been rebuilt, if it has the original pads on the ends of the selector forks, the atf attacks these, as they are made from compressed type of paper, gear oil is ok on these.
Another reason for gear oil is synchros need friction to operate effectively, they still get a bit with gear oil, and it has better shear properties as was designed just for this application.
Fully syn multi grade is fine in the diff, maybe that's all the had ?
tabetha

daviddunlop83

iTrader: (7)

As far as i know it is the original box with 59k on it and it drives fine. So would you recommend using 75/90 fully syn gear oil in both the box and the diff to avoid doing any more damage to these pads in the box? Or stick with the Ep90 for the diff?

Cheers

tabetha

I would use EP is the diff(lsd oil) mad use fully syn gear oil in the box.
I don't know how long this apparent problem takes to manifest itself, but there are over 30 variations of T5 box alone!
tabetha