Overfilling differential

[SLOTAO]

I replaced the fluid in my trucks rear diffential and filled up a little over 3 quarts. I read anywhere from 3.5-3.7 is full. I drove around a little then refilled the remaining 4th quart.. there was room for more.. Is there a problem with having 4 quarts in the rear diff?

Rich

 

[Crumm]

Drive around a little more than a little to get the oil up to operating temp then pull the fill plug after it sits for a few minutes. If there is room for more add more, if it runs out let it. You don't want it way overfull or low for best diff life and performance. If it is low the wheel bearings will suffer from fluid starvation.

 

[BJS]

unless you've stood your truck up on end you aren't going to overfill the rear diff such that it causes a problem.

When I change my rear diff fluid I specifically park with the nose of the truck pointing up a hill so I can get a bit extra in there. The 10.25 sterling is notorious for having bearings for a snack if the fluid is low. Ask my brother he just toasted his in his wheeling rig because he didn't keep on top of an axle leak.

On a related and somewhat important note as to why things do what they do. If you park the truck and pump the rear full of fluid from completely empty then it requires some time for the thick gear oil to pass through the bearings so typically 10 - 15 minutes later you will be able to put more in simply because it has now gone through the bearings. In my vicarious experience this difference in fluid level is enough to accellerate bearing wear.