Differential low on fluid n noise, damaged?

Only 1 quart low? Doubt that caused any problems at all. There's so much oil being slung around in there when driving.

Did you happen to have your interaxle or diff lock on by mistake?

Either that or your diff was already suffering a failure and its just becoming noticeable now. Either way I honestly do not believe being 1 quart low contributed much to it. Unless you have an active leak the diff should have been at that level since the last time it was checked/serviced. Diffs and gearboxes don't consume oil like an engine can.

 

What is a normal front diff temp for you? 200 is not that high. You might be right but how do you know the humming is coming from the front diff? Your assuming the gauge is accurate. Chunks would come out first. I would be more concerned with how much fine silvery stuff is on the magnetic plug and how silvery the fluid looks. Fine, smooth, silvery stuff would be bearing material. I agree with AModelCat that 1 qt would not make much of a difference and would not have caused a failure.

 

Changing your oil isn’t going to help. It’s going to be a waist of money. Kick your power divider in an out at road speed see if the hum goes away

 

No but if you have a bad front diff when you kick power divder in it will quite down

 

If your power divider is bad you are gonna have lots of slack or play at the yolk into the power divider

 

No it says don’t engage if a wheel is spinning. Road speed doesn’t hurt it. Kicking it in and out while in a straight line Line and good traction doesn’t hurt it. While spinning yes it’s a death sentence because it locks front to back. So if one’s spinning extremely fast and is locked to the one with traction then it’s a sudden stop