Hi there

Everyone seems to have a different answer.

How many quarts of 75-140 oil go into the rear-end (differential)?

 

Buy 3 quarts and a bottle of friction modifier.

 

Use royal purple, posi trac additive already in it.

 

so how many quarts does it hold? 2.something?

 

Mine holds more because of the TechCo Watt's link cover. I think it's about 2.5 quarts + the friction modifier.
I use the Ford full synthetic gear oil with the Ford friction modifier. Not a fan of Royal Purple but that JMO~

 

I just had my gears changed yesterday and the rear end held 3 qts of Royal Purple 75W140 which includes the friction modifier. So, 3 qts to fill the 8.8 inch rear end.

 

I've been told you fill it up until it starts overflowing from the filler hole. About 3.5 quarts for me. It overflows out of the vent on the top of the axle later, but I don't think it hurts to overfill, it's not a pressurized system.

 

Nope, just messy...