Ok so its time to change the rear diff fluid. What fluid and weight is everyone using? I was thinking of going royal purple...
i would just use a name brand orig style lube. i believe they are gl 80 to 90 weight. if it is a posi don't forget the posi additive gm 4 ounce bottle. get a hold of jd race on the board. he rebuilds rears. jdkarnes
As I tell everyone that is worried about fluid. Fluid will not make or break your rear diff....LACK OF OIL WILL!!!! lol. I you have a limited slip posi unit you really should try to stay clear of synthetic fluid as Eaton and Auburn have a disclaimer in their warranties ' NOT TO USE SYNTHETIC'. WILL VOID WARRANTY. So if you have a open rear or a torsen (helical worm gear) type posi synthetic is fine. All friction type posi unit will require the Limited Slip additive to perform to its potential and stop clutch chatter. (this is mostly becuase of the metal to metal clutch and cone contact.) On Ford composite and Eaton carbon fiber clutches synthetic does not seem to affect as much as in the metal to metal type. Weight of oil: well this again with a grain of salt... I always say in the south hotter temps go with 85-140 weight oil and in the northern cooler temps 80-90. But again if your drag racing a lighter custom oil could be good for that little extra edge... Fluid level: PLEASE PLEASE please. Check the fluid level at least once a year. Believe it or not the fluid does dissipate/evaporate from air exposure from the breather vent- not much but.... heat also will break down the fluid and burn it up too. AGAIn not much... A small leak might leak more than you think. The rear diff does not ask for much keep the oil level up and your diff will live a long time. Taking for GRANTED that it was built correct in the first place. Good luck on the fluid change. Jim
