Ford 9" oil leak

[Texasdoc]

I'm getting tired of these slow leaks....

I bought a new 9 inch rear for the cobra during the build from a local vendor. However, shortly after purchase the seller went out of business and moved. I'm not exactly sure which LSD I have inside, but there is one in there.

I have looked all around this thing and don't find a fill level hole. He was supposed to put one in. There is a vent on the top of the housing that I used for filling, but I can't tell how much fluid to put in there. After searching the forums, it seemed like 2 quarts plus the modifier was the average consesus - so that's what I put in.

Now, I keep getting some fluid leaking out of the vent. I'm sure it is not coming from the drain plug. I'm considering changing the vent to a threaded barb, connecting a rubber hose, and raising the vent higher, but I still don't know if the right amount of oil is inside. I don't want to overheat due to too little oil.

Since I have a 9 inch and can't just take off the diff cover, how do I tell if there is the "right amount" of oil inside? What is the right amount of oil? Should the oil come up to the bottom of the axle tubes? (I can take out one axle, make sure the rear end is level, and pour 4 quarts in - whatever comes out is too much.) Without knowing the exact parts, I can't call the local transmission shop and ask them.

Any thoughts on oil level in a 9 inch?

[Rick Parker]

The Ford 9" is widely copied my many aftermarket drivetrain companies. However the OEM Ford Gear carrier has an oil fill plug on the LH side of the Gear Carrier "Pumpkin" or "Chunk". This is the fill port and used also to detrmine when it was full as the lubricant flows out when full. 2.8 qts is what I have read is necessary. When constructing an axle assembly threaded ports are often welded on the top & bottom for a drain and fill point. The vent can be relocated on the axle tube and a hose attached with a filter up high. Here is a good photo of my setup, the curved hose fit pefectly:

You can just barely see the edge of the OEM fill pipe plug behind the braided hose. As described above it is used for fill in standard application, I added the two bungs top & bottom that make it easier, and allow a little higher oil level.

[Texasdoc]

Yes, I see in your photo that you have the "level" plug on the carrier. I have the vent on the axle tube that I use to fill, and a drain plug on the bottom of the housing. That's it. I *Do Not* have that plug on my carrier (circled in red). Without this plug on the carrier or on the back of the housing, I don't know how much oil to put in.



I will try to attach a barb/hose/filter to my vent hole like you have done here to help decrease the leak, but that still doesn't help with the oil fill level.

[Jac Mac]

As there are two,possibly three variants of 9" Axle houseing designs & one in particular holds a larger amount of oil at the level reqd you should ascertain which housing you have, the large capacity one has tapered pieces on each side that extend out onto the axle tubes by approx 6 to 8 inches each side.

[Texasdoc]

Hopefully this helps...

All the receipt shows is the following. There are no other brand names other than Moser. I can't be sure that is what it is, but that is what the receipt shows. Not sure what Torino BB ends are but Google suggests they are end flanges.

Moser Axle
3.70 gears
31 spline LSD
11" brakes
Torino BB ends
Vent, drain plug

I looked at the 3rd member (carrier?) and saw C5AW. No "N" stamped on the front. Single ribbed case. No drain/fill/level plug.

The housing looks like this:



NOT LIKE THIS:

[Jac Mac]

This pic should give a better idea of lube height/level in the unit, note the level hole is a bit lower than the axle tube diameter so filling until it runs out the axle tubes will be too high, I dont see anything other than removing the diff head assy & fitting a level plug in the axle housing, if it has not got a drain plug you could fit one of those as well, You could drill & tap for a 1/4" npt type taper plug in the axle housing rear cover at the correct height with some grease to capture swarf etc, or better still drill a small 1/4" hole & use a taper punch to 'flare' the hole inward prior to threading for 1/4 npt to gain a couple of threads.

[vector1]

get a piece of #9 wire and shape it to stick in one of the rear holes to find the level, will give you a good idea. i wouldn't worry about being higher than the bottom of the axle tubes, fluid running through the tubes can keep the bearings at the ends lubed. as long as you don't have any fluid coming out the ends or the front seal i wouldn't worry, put the extension on the top breather, even the production stuff does this.

[olddog]

The wheel bearings on my 9" (and all that I have seen) is a sealed greased bearing. The oil in the housing does not come in contact with the wheel bearings.

There is an oil lip seal that rides on the axle. Too little oil and it will fail. Too much and it will leak.

I have seen a lot of 3rd members for sale at swap meets, and I have never seen one without the oil fill hole. I'm not saying it is impossible, but it is much more believable that it was missed. I would like to see a picture.

[Texasdoc]

Originally Posted by olddog

I have seen a lot of 3rd members for sale at swap meets, and I have never seen one without the oil fill hole. I'm not saying it is impossible, but it is much more believable that it was missed. I would like to see a picture.

Really? You want pictures? Ok.

Right Side


Left Side


Rear Housing


Vent/Fill



Like I said. I have the vent that I use as a fill hole. I have the drain on the bottom of the housing. No oil level plug.

Thanks. Tom

[vector1]

i thought the earlier pic of the two holes on either side were yours, that is jacked up!

[FWB]

some , like yours, 3rd members don't have a fill plug. in your case use the bolt/stud on the drivers side, which is a slight bit lower than the 3 o'clock position as your fill hole, fill the lube up to the bottom of the hole and call it done.
the easiest way is with a suction gun, it will pull fluid out or push fluid in.
they have a little hose end that will fit into the hole when you pull the stud out

[olddog]

Tom my apologies if I offended you. Well now I have seen one. I'm not sure what I would do. I would be tempted to pull the axles, jerk the third member out, and have it drilled and tapped. Quite a bit of work, but it would be fixed forever. Not sure it is worth it.

[Texasdoc]

No problem, not offended. Thought about taking it apart and adding one - not sure its worth it either. I would feel more comfortable knowing the right amount of oil was in there.