Gear oil question

[Frid]

Just got done putting 373's in my rearend. was wondering which weight gear oil i should use. ( which weight is put in it from the factory preferably)

 

[slowbra99]

80W-90. they will also tell you to get additive for the limited slip differential.

 

[Lumpydogs]

Differential Lubricant
80W-90 GL-5 Gear Oil (Mustang & GT)
75W-140 w/Friction Modifier (Cobra)

 

[Charles236]

I'm using 75w140 synthetic (Mobil 1) in my differential. I drilled and tapped the pumpkin for a drain plug so that I could change the gear oil, but with a TrueTrac differential the gear oil doesn't have to deal the heat from clutch plates slipping, so I don't change it very often.