differential oil level

[Me2carcrazy1]

I am changing the differential oil for the first time. It's a Dana 40, 9". I have owned Bronco for 5 years. Recently, I noticed that it was leaking a few drops of oil. I decided to check oil level. Unscrewed the filler bolt and oil came running out in a constant stream. I put the filler bolt back in when the it turned into a dribble.

I thought the fluid should never go above the filler hole. When it starts to come out when you are filling you stop. Is that correct? I looked at the rear axle seals and there is no oil leaking there. Looks like it the gasket that is leaking. I will replace that soon.

Thanks for you help.

 

[Yeller]

That's fairly normal. Often, they get filled parked at a different angle or they are using something that pushes in a little more above the hole. Nothing to be concerned about. I'd be far more concerned about it being low. In lifted applications it is very common to over fill the diffs so the pinion bearings get adequate lubrication, albeit rarely necessary.

For gaskets there are only 2 that I will use for a differential. If a gasket is deemed necessary for future work Lube Locker is the only one to buy, they are reusable and work very well. Otherwise, it is Right Stuff RTV, if it leaks it's because its broke or falling off. I use Lube Locker on race cars or new builds and Right Stuff on everything else.

 

[Me2carcrazy1]

That's fairly normal. Often, they get filled parked at a different angle or they are using something that pushes in a little more above the hole. Nothing to be concerned about. I'd be far more concerned about it being low. In lifted applications it is very common to over fill the diffs so the pinion bearings get adequate lubrication, albeit rarely necessary.

For gaskets there are only 2 that I will use for a differential. If a gasket is deemed necessary for future work Lube Locker is the only one to buy, they are reusable and work very well. Otherwise, it is Right Stuff RTV, if it leaks it's because its broke or falling off. I use Lube Locker on race cars or new builds and Right Stuff on everything else.

Thanks for your comment. I feel a bit relieved after reading your response.
I checked it in my level garage floor. My Bronco has no lift. I also looked to see if maybe I had a flat tire causing it not to be level. LOL
My neighbor does a lot of 4 wheeling . He agrees that Lube Locker is the only one to buy. Looks like I will have a project for this Labor Day weekend!

 

[gnpenning]

Do you or the previous owner do many water crossings? They can fill with water and do what you described as well.

When you checked had you just got done driving it? Front or rear or both over full?

Hopefully just overfilled with oil.

 

[Me2carcrazy1]

I’m 99% sure no river crossing based on where Bronco spent its life. Oil was also clean with no water indicated.
It did sit for a week before I checked it. Should it be checked immediately after driving?

 

[Shimmy]

since this sounds like you haven't cracked open the rear axle cover or shafts before just be prepared for further replacement parts. axle bearings, seals?

 

[spap]

Are you going to pull the 9 inch rear axle, just to change the gear oil? Which Is the best but I would look at the gear oil to see how it looked.
how did the oil look when it was spilling out.

 

[Yeller]

I meant to say something about the oil.... if the oil appears clean, unless there is a leak, chances are it has more anti wear additives than anything you can buy today, unfortunately. So there really isn't a reason to change it just for being old. I know a few guys that peruse salvages for low mileage pre 1980 school busses and such to rob them of their gear oil.

Word of wisdom about gear oil, differential gear oil and transmission gear oil are not the same. Valvoline markets an oil they have cross listed as both, it always makes me question how good it is in a differential. Differential gear oil will contain Sulphur, Sulpher is bad for bronze bushings and synchronizers in transmissions and transfer cases. Oil rated GL4 is for transmissions and transfer cases, GL5 is for differentials.

 

[Me2carcrazy1]

Gear oil looks good. Doesn’t look old and no sign of water. I am not looking for a big project so I might just take it to my mechanic to do it.
I have read a lot about diff oil to use. Just that made my head spin. I figured out what I needed but it is out of stock around here.
Appreciate your comments.

 

[spap]

If it looks and you want to change the 9 inch oil you can pump it out and replace it, with out pulling anything, the front Dana 44 has a plug too