VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 31 Chevy with high Differential pressure

I've had a problem with the differential blowing oil out the rear seals for a long time. This started when I replaced the rear wheel felt with a newer type rubber seal. I've put a taped hole in the top of the differential with a small hole in a plug but it just blows oil out the plug. I've even tried a small copper tube a few inches long thinking the pressure would relief and the oil run back but that doesn't work. Any one have an idea how to fix this.

Same at my 1931.
I think it is not a problem of the differential at all.
Oil is coming from transmissions rear end and if the diff. is filled up the only way is left and right to the outer axle.
I think I have to find a solution to get the oil leak and rear end of tranny stopped.
check oil level of your tranny and I am sure there is a lot of oil missing.

Stefan

I have put seals in the tranny and tube (newer type) the differential is not a high level of oil. So it seem that its not coming from the tranny.

if you put a very small vent hole in a area above where the carrier is slinging a lot of fluid the hole will be blocked by the heavy fluid. I drilled a small hole about 2/3 down the axle tube on top and filled the hole with a small nail with a flat head. the outside dia of the nail shank is smaller then the hole. I'm running sealed bearings.

The small hole you spoke of is in the axle tube not the torque tube right? Mind seems to have blown oil out the left wheel, suppose it's the rotation on the wheels that made it come out this side. You think I should drill the left side of the differential tube? What dia. was the hole, do you remember? This sounds like the way to go and I thank you for the tip.

A vent 1/3 to 1/4 of the distance from the fron to back of the torque tube should work. That location in your passenger or one between center section and rear wheel should be the best options to vent but not loose fluid. If you put the hole too close to the circulating fluid it will put some near the hole and the exhausting of air will force it out particularly as the fluid and housing is heating from use.

There was an answer to this very problem sometime back and the remedy suggested that I have done to my 31 was to drill a 1/8" hole in the very top differential housing cover bolt and insert a cotter pin, bending the tabs back on the threaded end and reinstall the bolt. It works.

hoppy

I did not understand from where there should be any oil pressure inside the differential?
I did never open mine, but as I understand the drawings in the manual, there is just some oil circulating because the ring and pinion gears rotate, cannot believe this could cause any pressure to pump oil outside???

Stefan

it's about a 3/32" hole approximately 6-8" from spring perch on the axle tube. left or right shouldn't matter but I did the right side. the hole diameter was determined by the size of the nail I had on hand.


the pressure comes from the heat generated by the meshing of the gears, heated air expands, a normal occurance. I was surprised there was no provision for a vent from the factory. Once I installed the vent I noticed a drip from the lower propeller bearing lock screw disappeared.

The reason that there was not a vent is the use of felt "seals". They permit gas movement but hold most of the liquid in place. Once you replace the ventilating felt seals with modern lip seals then some pressure relief needs to be provided.

back in the day that appears to be the industry's approach to lubrication containment, "hold most of the liquid," before the days of neoprene and nitrile

Thanks Dads 31, I have made the changes today that you have noted and so far this seem to be the right fix. Time and more driving will tell. Thanks to all that have confirmed that pressure will be a problem with lip seals when you replace the felt seals.