The Stovebolt Site Forums The Shop Area Driveline pinion seal leak

one of my winter projects is to get pinion seal on rear end fixed. tried last summer, pulled it apart replaced with identical seal from FLAPS, reused the felt seal as it seemed in good shape. took it for a ride and still had a leak when it got warm. questioning if it was the wrong seal all along? Title for truck says its a 1948 3100. But, serial #'s on engine and tranny both say 1952. 8 bolt rims all around. I can only assume someone took a 1948 body/title and put it on a 1952 3600 chassis. hoping someone can identify this rear end to confirm and then attempt to find correct seal. Raised numbers on differential carrier: 3682126 stamped letters on top of "pumpkin" are very hard to read but I believe 16716? One piece of info I dont have on hand is weight of gear oil I refilled with. Could simply switching to a heavier weight oil remedy this issue? It only leaks when hot leaving a rooter tail of oil spun up onto underside of bed and then a small puddle of garage floor.

Only leaks when hot could mean the vent is plugged and the oil is being pushed out
Check the vent and make sure it open and clean
-s

What 2Many said plus a common repair is to put a Speedy Sleeve over the seal worn area of the pinion. Worked for me.

Good Luck

RonR

Sounds like you have a later than '52 rear axle if it has an open driveline. I believe a '52 3/4 ton still had an enclosed (torque tube) propshaft setup from the factory.
Like was said above a speedy sleeve on the pinion yoke should fix you up. You may have to pull the yoke and measure the diameter to get the right speedy sleeve. Also, when reassembling, a bit of sealer behind the nut helps to prevent oil from seeping thru the splines.

I believe the 3/4 & 1 ton had torque tube off the transmission & open drive shaft from the carrier brg. on back.
If the pinion brg has play in it the seal will not hold.

George

You are correct, George. I just checked the service manual.
My dad had a 51 GMC 3/4 ton as his shop truck and I remember it needing the rear end rebuilt, I vaguely recall the guy at the repair shop (fondly known as "Greasy Bob" ) using dad's pipe dope to check the gear pattern and turning the driveshaft at the end of the torque tube. Maybe GMC 3/4 ton's use the torque tube rear axle. I'm sure somebody with a GMC here at Stovebolt could confirm or deny that.

My '52 GMC 152 (3/4 ton - they only made them in one wheelbase) has an enclosed driveshaft coming out of the transmission that joins to an open driveshaft at a hanger near the rear of the cab down to the rear end.

All of my 1 tons are a universal joint behind the transmission
No part of the drive shaft is enclosed
The drive shaft is two parts
But maybe that’s not how the USA made them
-s

In my defense, that memory is back in the fog of 60 years ago.

The U-joint yoke often has a groove worn from the seal and a speedy sleeve will fix that BUT they also suffer worn splines from mis-matched U-joint angles or rough shifting or washboard roads. Then they vibrate and will not seal. Make sure you tighten the pinion nut tight enough to hold the splines from moving if they are worn. I don't know if yokes are available to fit the HO52/72 axles. Why GM didn't just run the open drive shaft all the way to the transmission on the 3/4 tons is a mystery to me but all I've seen are closed from trans to carrier bearing, then open. One-tons and up are all open DS trans to pinion.