The Stovebolt Site Forums The Shop Area Driveline Leaking Torque Tube at the Rear End

Anyone come across this situation before? I've put about 165 miles on the truck. Apparently, a good warm-up will show you where the weaknesses are......

It's a 1947 3100 with the original three speed transmission.

See if your differential is overfilled. It could be leaking at the axle seals too. The transmission might be leaking oil past the old leather seal, down the torque tube, and into the differential. If so, either install a new okie bushing or check your oil levels often and learn to live with it. Good luck!

I am going to presuppose that like nearly everything Chevrolet pressed the torque-tube into the carrier casting and secured it with rivets. Chevrolet just loved to press things on. It has been my experience owning a 1954 Belair for most of my life, and now a 54 3100, that some seepage is normal. There was not a high concern back in the day like it is today in get things sealed up well. Judging by the photo this is seeping more than it should.

I would first check the breather mounted on the top of the axel housing on the left side to see if it not clogged. You should be able to turn the top of the breather freely: it should practically rattle when flicked with a finger. The breather allows expanding air to escape when the differential warms up while the truck is being driven. If it is not moving freely it is likely clogged, and it might be a case that the warming expanding air inside the differential is forcing grease out the weakly sealed points of the differential such as the torque-tube. If the breather is not clogged you will need to determine a way to seal the torque-tube. I am hesitant to advise on how to do as I haven't had this situation on my own vehicles.

Walt Williams
La Verkin, UT

Thanks for your replies. The differential seems to be adequately filled and the transmission is pretty close to full (top gasket around the shift is seeping). I'll address that later.

I went looking for that breather on the axle housing. It's missing and the hole was plugged with many years of road crud. I cleaned it out and it looks to be an 1/8" pipe threaded opening. Does anyone know where to get a threaded replacement? I haven't been able to locate one. They are referred to as an axle vent or rear differential vent, correct?

Hopefully, this will solve the problem. If not, Hotrod Lincoln suggested a thorough power washing with an engine cleaner and a layer of silicone-type sealer (RTV) to the joint where the tube meets the differential housing.

Thanks again,

Andy,

The vent valve you are looking for is available through Classic Parts. The part number is 93-242. Hope this helps.

Tim

Here is a picture of the original for you.
https://www.flickr.com/photos/advance-design_parts_co/14177411321/in/album-72157631868452754/

Hi Andy,

Where on the axle did you find the vent hole? I was looking for the vent on my truck, and was not able to locate it. Since we both have '47s with torque tube rear ends, I though you may be able to help me narrow my search a bit.

Thanks,

Bill

There's a breather vent on EBay as we speak. Item number is 151502382759. Good luck!

Driver's side rear axle about a foot outboard of the differential. Sits on top and looks like a top hat.

Hi Bill,

Sure, mine is on the driver's side on top of the axle about six inches from the rear end housing. It was missing and full of road grime.

Take care,

Another approach to axle housing venting is to put a tubing nipple into the housing and run a piece of rubber tubing up inside a frame rail. This will prevent water getting into the housing if the rear end gets submerged at a boat ramp, deep puddle, etc. The top hat type vent will siphon water into the housing if a hot rear end encounters deep water after a highway run. I've seen it happen repeatedly when some of my bass fisherman customers launched their boats after a long run at highway speed. Water and rear end lube does not play well together!
Jerry

Thanks All,

I'll look for the vent on mine this evening. I don't recall seeing a "top hat" in that location so this may be another opportunity for me to use my growing collection of extractors.

I like the tubing suggestion; it isn't stock, but neither are the readily available plastic vent tubes.

Best regards,

Bill

Vent hole found, crud-fill confirmed. I didn't have the time or inclination last night to determine if the vent is broken off in there or simply removed.

Another item for the weekend to-do list

Glad I found this post! Curiosity made me go look at the breather on my axle and all that's there is a plug. What the heck? I've been running this truck for many, many years and did not have wisdom regarding a breather. Should I replace the plug with a breather at this juncture? Thank You!

yes

Okey Dokey tclederman, hope I can locate one - Thanks!

Those little vents are spendy and then 10 dollars to ship - yeesh!

I just fashioned a temporary vent using a barbed fitting, a large vacuum cap and a washer. The vacuum cap slides up and down on the barb shaft held on by a split flat washer. No dirt, no pressure. It'll do until I can get the real thing.

I’m needing a spider gear kit and bearings for my 1952 Chevy 3100 truck! Any information will be appreciated

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