Differential oil leaks to drive shaft torque tube

[Geo.T]

I am adding 600w oil to the differential regularly which is apparently leaking into the drive shaft torque tube. From my knowledge and review of literature, there is no seal for stopping leakage through the differential pinion bearings until reaching the oil (grease) seal on the transmission side of the speedometer gear.
When disassembling various model A's in the past, I have never seen a torque tube filled with oil.
The reason that I raise this issue is that about four years ago, I built and installed a Volvo overdrive (OD) immediately in front of the differential. It works like an absolute dream but I now have this problem of differential 600w oil leaking into the torque tube which I didn't expect. The oil then leaks out through openings where the torque tube attaches to the OD. I have installed a "catch basin" at this point to collect the leaking oil.
The only solution that I can think of is to somehow seal the connection of the torque tube to the OD (not an easy task) and the simply let the torque tube fill (and stay filled) with oil to that point .
I am still mystified at the amount of 600w leaking from the rear end.
Any advice would be appreciated, in particular from others who have cut the torque tube to install an OD.
Thank you in advance,
George

[SeaSlugs]

well if the torque tube fills and stays filled more than likely your axle seals will fail and ruin the brakes once the pumpkin fills up.

[saladbar]

hi had the same problem. there is a small pin size hole in the trans shift tower that I think is a vent for rear end trans mine was plugged solid. john

[BRENT in 10-uh-C]

A couple things to look at;

Is the rear end mounted in the proper pinion angle? In other words, if the rear spring is reversed, -or if the driveshaft is sitting more horizontal, this basically places the fit plug higher and the pinion bearings lower in relation to the centerline of the differential.

Is the flange surface of the differential housing and the torque tube machined in parallel?

[Mitch//pa]

dont park on a steep down hill either

[redmodelt]

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As Brent in 10-O-C said, unless the torque tube is sitting flat any oil that migrates up it should flow back down. You might need a vent added to the rear end.

[Geo.T]

Thank you gentlemen. I am going to try a small vent to drain off any air pressure build up, possibly caused by foaming in the lube.

[Tanglfoot]

If you have a Volvo OD and the diff/torque tube is gaining oil then the rear seal on the OD unit needs replacing.

[katy]

Maybe the lube is trying to establish it's own level and you keep topping it up and the rear end keeps pushing it out. Try running it at a bit lower level, but not too low, and see if it stabilizes.