Consequence of Over-Filling Rear Differential

[MMead]

I've read several threads discussing the proper fill level and it seems to be about a quarter inch from the fill hole. Last night I filled mine but instead of watching the level, I simply poured in 122 oz like the old TSB said to do. This brought the level just under the fill hole, but above the quarter inch level that is recommended.



I've heard overfilling can cause foaming, but does anyone know for sure if this slight over fill will cause any problems? Is it worth trying to get some of the fluid back out? Thanks for any help.

 

[Bertram65]

I would not worry about it, I fill till it comes out the hole, there is no way 1/4" is going to make any difference.

 

[sag2]

Actually there is a fill line on the cover below and to the side of the fill hole. Many guys are running over full, but you can risk the foaming. However, I would be much more worried about overfilling an auto trans than a diff.

It would not hurt to remove the extra fluid. Also if you get a rear axle seal leaking, you will ruin the shoes and make a mess that would not otherwise be there if the level was proper.

 

[MMead]

Sag2,



What happens when you over fill the transmission? I lost some transmission fluid the other day putting in a new transmission cooler line and when I checked the level it looked very low. So I added a quart and now it looks a little high. Am I in big trouble?

 

[Bertram65]

Actually there is a fill line on the cover below and to the side of the fill hole. Many guys are running over full, but you can risk the foaming. However, I would be much more worried about overfilling an auto trans than a diff.

It would not hurt to remove the extra fluid. Also if you get a rear axle seal leaking, you will ruin the shoes and make a mess that would not otherwise be there if the level was proper.

There is no fill mark on the '03 trucks, the fill is 1/4" below the hole plus or minus 1/4" acording to the manual.

 

[Alan Reagan]

Sag2,



What happens when you over fill the transmission? I lost some transmission fluid the other day putting in a new transmission cooler line and when I checked the level it looked very low. So I added a quart and now it looks a little high. Am I in big trouble?

Your next question would be "Did I blow a seal"?

 

[MMead]

Blow a seal?? That doesn't sound cheap. If it is a little full is there any easy way to get some fluid back out, or do I have to drop the pan?



BTW - by a "little full" I just mean that the transmission dip stick is right at or just slightly over the max line after interstate driving.

 

[Gary - K7GLD]

Common sense tells me that the difference of a quarter inch in differential lube level is VERY unlikely to create any additional "foaming" of lube... And whether the lube level is "on the mark", or a quarter inch higher is sorta moot - considering that these vehicles spend LOTS of time being parked or driven in unlevel conditions, around curves, etc. The axle seals either function properly, or they don't - and the difference in lube levels with leaking seals will probably give the brake pads and rotors an oil bath either way...

 

[WCPoe]

Here is a small hand pump I used when I overfilled my transmission. The tube slides inside the dipstck tube and you can pump out what ever amount you need to. It's cheap too.



http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=3878

 

[JHardwick]

I'm no mechanic, but aren't these rear ends floters?

 

[rrl989]

Within a week of overfilling my Dana 80, I had a leaking DS axle seal, & the pinion seal.



Ron

 

[Gary - K7GLD]

Within a week of overfilling my Dana 80, I had a leaking DS axle seal, & the pinion seal.



Ron

You hadn't by any chance switched to a full synthetic lube at the same time, had you?

 

[Eric_77]

Sag2,



What happens when you over fill the transmission? I lost some transmission fluid the other day putting in a new transmission cooler line and when I checked the level it looked very low. So I added a quart and now it looks a little high. Am I in big trouble?

Here is some info for ya on the over filled transmission.



http://turbodieselregister.com/forums/showthread.php?t=120667&highlight=transmission

 

[macdaddy]

Jeeeeeeze!!!!!

Are you guys talking about axels or transmission's?. Gary is correct to say that 1/4" in difference will make absolutely no difference as it pertains to the AAM 11. 5 rear axel. As far as oil emulsion (foaming) there is always a little, no worries. If the entire axel becomes emulsified such as the case where water contaminates the oil then you have problems .



One point to make regarding axel seal failure's, allot of the time and one of the more over looked preventive maint items is the axel vent line, it should be cleared at least every oil change. This insures that the axel can breath as the oil temperature fluctuates.



Mac

 

[sag2]

Your right, 1/4" (or even a little more) is not going to make much difference in the axle. The trans being over full (probably and inch or more) will allow fluid to reach the spinning gear case and other rotating parts. That beats the fluid into a froth and since air can be compressed, the clutches do not apply solidly.

There is room for error on all this stuff, but I always felt, do it the way the manufacturer says. They test them and warranty them based on that.

 

[JHardwick]

I'm pretty sure MMead was talking talking about his rear end. In that case, level to the fill hole to 1/2" below is acceptable. And beside there are no axle seals in a full floating rear end.

 

[Joseph Donnelly]

There are axle seals at the hubs on a floater. The outer bearings are lubricated by diff lube traveling along the axles to them. Best level is between the bottom of the axle shaft and inside bottom of the axle tube; right where Mag Hytec's dipstick puts it. Leaks are mostly a factor of the type of lube and whether it has enough seal softening/swelling additive (synthetic lubes) or naturally occurring compounds (if dino lube like LE607). Good axle lubes don't foam up like ATF could.

 

[radar doctor]

This sounds good to me... what's next

 

[rrl989]

You hadn't by any chance switched to a full synthetic lube at the same time, had you?

No synthetic, replaced with same 80W-90 and the modifier. Overfilled, until it rolled out the filler plug threads. Since I did it, I know it got by the seals because I overfilled it. Both leaked at the same time within a week.



Ron

 

[DGFoster]

I used a pump that I had ti pump some out,now it is about half inch from fill hole. .