Rear diff oil capacity

[kcjaz]

I know the capacity of the rear differential is 4.39 to 4.49 U.S. quarts according to the FSM. When I changed the gear oil today. it only took about 4 QTs. I was filling it with the truck on my lift so the axil was at full droop which would rotate the diff a bit so I lowed it to the floor and it took a bit more but still not what the FSM says. This is the first time I’ve changed the diff oil since I had lockers installed. Would lockers reduce the oil capacity a small amount by taking up some space?

 

[CanadianRockyCruiser]

I know the capacity of the rear differential is 4.39 to 4.49 U.S. quarts according to the FSM. When I changed the gear oil today. it only took about 4 QTs. I was filling it with the truck on my lift so the axil was at full droop which would rotate the diff a bit so I lowed it to the floor and it took a bit more but still not what the FSM says. This is the first time I’ve changed the diff oil since I had lockers installed. Would lockers reduce the oil capacity a small amount by taking up some space?

A rear locker would probably displace some of the differential fluid. It's also possible some had run down one of the axles when it was lifted, and settled when you put her down. If she's full, you are good.