[bry593]

Sorry to bring up an old thread, but...

This is absolutely true. The HO52 / HO72 oil level as governed by the cover fill port IS BELOW the axle tubes.

How do I know? Well, I completely rebuilt my '71 HO52 and then filled the diff on a level surface to the port. I drove it about a mile and realized I had a brake issue. To fix the brakes, the axles and hubs had to be removed. When I pulled the axle, I was shocked to find the axle flanges were dry! There was no oil at the hubs! Good thing I "sorta" packed the bearings with grease.

To fix the issue, I jacked up the axle so I could add 1/3 liter additional fluid, then parked the truck sideways on a hill, both directions.

Anyway, BE WARNED!!!! Do pack the bearings with grease and do tilt your truck to get some oil out to the hub bearings during the initial break-in period.

I assume the design oil level is low so as to reduce oil foaming and heat build-up. The Engineers assumed the oil would eventually flow to the hubs due to centrifugal force when cornering.