What happens if you overfill a (Chevy) rear end?

[Loobed]

What would happen if you overfilled a rear end differential by 1/2 quart? I am guessing that more oil would go in the axle tubes and raise the overall level very little. I can't think of anything beside foaming or having some come out the vent.

 

[OtisBlkR1]

year ?

I only ask becouse older chevys you could fill them till they overflow, newer ones your suppose to keep 10mm below the fill hole i believe.

 

[Rand]

foaming, aeration , loss of mpg, oil shooting out the breather.

 

[oggb]

It'll probably foam if you overfill it by too much - that's not great for it, but it's not a death sentence.

 

[INDYMAC]

I guess if the breather was clogged, the seals would take a hit.

 

[KB2008X]

Besides foaming, overfilling the differential can also allow too much gear oil into the axle tubes, as you mentioned. And that can lead to the gear oil leaking out of the axle seal under certain circumstances. Brakes and gear oil is not a good combination.

Draining or sucking out gear oil, even though it is not a fun job, is preferable to the unnecessary complications that can develop and the additional repairs.

Keith

 

[dubie2003]

Most diffs are designed to fill till they puke. How is yours setup? Is it lifted? This is how most goof.

 

[Loobed]

Originally Posted By: dubie2003
Most diffs are designed to fill till they puke. How is yours setup? Is it lifted? This is how most goof.


The manual says:

"The proper level for the 1500 Series is from 5/8 inch to
1 5/8 inch (15 mm to 40 mm) below the filler plug.
The proper level for the 2500/3500 Series is from
0 to 3/8 inch (0 to 10 mm) below the filler plug.
Add only enough fluid to reach the proper level."


I think I am about 1/2" below the fill hole.

 

[KB2008X]

You need to be sure what the actual level is. Get an old wire coat hanger, a pair of wire cutters/pliers and make an "L" shaped tool with the short end 1" long. Scratch the short end with a sharp tool at 1/4", 1/2" and 3/4" and crawl under and check it. Angle the short end in and lay the long end on the threads of the fill hole. Try to check the level on the tool as soon as it comes out.

It may take several attempts before you have the tool just right. Leave enough on the long end so you can loop it around to hang from a nail for future use.

If raising the rear-end off the ground makes it easier to deal with go ahead and do that. Tires up to 6" off the ground should be OK - it won't affect the reading enough to make a difference. Be sure to use the correctly rated jack stands.

If you have the 1500 which calls for 5/8 to 1-5/8 then you want to shoot for 1" below the fill hole.

Keith

 

[mechtech2]

Checking the level hot or cold will make a difference.
I don't think foaming is an issue with rear ends like auto trannys.
The gears and bearings are already spining in fluid. 1/8' more won't matter.

Actually, I would find it hard to overfill a rear end by 1/2 qt - how'd you do it?

 

[Loobed]

Originally Posted By: mechtech2


Actually, I would find it hard to overfill a rear end by 1/2 qt - how'd you do it?


It is not hard. The truck was parked on a slight incline.

 

[dailydriver]

It is also not hard to do with T/A, Mac, or whomever's alloy covers used on GM 10 and 12 bolt axles, since they have a filler hole WAY ABOVE the filler hole on the side of the pumpkin.

One could probably get MORE THAN a 1 quart overfill by filling the diff to that filler level!