9" lube level - no fill plug

[WG]

I have a modified 9" in my '71 Bronco. It has no fill plug in the third member. Is there a way to check the lube level/add lube using one of the pinion bolts? Or some other method?

 

[Bronco-Brian]

Does it have the vent in the top of axle tube? You could access there?

 

[Apogee]

Roughly speaking, a Ford 9 takes about 2.5 quarts of oil, however it depends on the housing type/shape as well as pinion rotation. I don't know of an easy method to check fluid height without a fill plug, though I added a fill neck on the top of my housing and an 1/8" NPT drain plug at the bottom seam when I welded on a back brace for easier service. Do you have any pictures of what you're working with?

 

[marshall godron]

Sounds like maybe a 66 housing?? The full plug was in the third member not the back of the pumpkin

 

[Broncobowsher]

Oil level just at the bottom of the axle tube. Just enough to see a flat spot on top of the pool of oil.

Had a custom axle built a couple years back for a work project. Had a lengthy discussion with the axle builder, did a lot of benchmarking of axles. That was where we agreed to an oil level. Low enough the axle seals are not over taxed (too much and the oil can push past the axle seals) but high enough the side bearings (and wheel bearings if wet bearings) will bet lube. Wheel bearings will get fresh splashes as you turn left and right. Side bearings are in the oil bath. Pinion bearings and gears are all submerged.