Per Zig's request I am posting pictures and text from the driveshaft seal replacement that Bill and Bill did today. The 3/4 ton GMC (and Chevy) trucks of the 48-53 era are unique when it comes to driveshafts. They have an enclosed front U joint and driveshaft like the smaller 1/2 ton trucks do, but about 3 feet to the rear the enclosed shaft ends at a hanger with an exposed mid point U joint. On the rear side of the mid point U joint is a splined slip joint that attached to an exposed rear driveshaft, through another exposed U joint that attaches to the pinion shaft on the rear end. Mine was leaking gear lube at two places, the ball cover at the immediate rear of the transmission and the seal at the rear end of the enclosed position of the driveshaft. Bill Brubaker kindly offered his air conditioned garage and tools for the job. I ordered part number 92-111, U-Joint Ball Gasket & Seals 35-54, from our host (FelPro ES72843 if you'd rather get it from your FLAPS) which has 4 Hydra-Matic to ball collar gaskets/shims (I didn't need these), 4 standard transmission to ball collar gaskets/shims (I used these), one ball collar to ball gasket (I used this) and one gasket that is used on the 1/2 ton driveline, but not of the 3/4 ton. We started by removing the rear driveshaft from the front driveshaft by taking the U bolts from the middle U joint. Per the manual we taped up the U-joint caps to keep from losing the needle bearings. The manual called for totally removing the front shaft before disassembling the components of the shaft. The big nut (1 1/2" socket that neither Bill or Bill had) looked to be impossible to break loose once the shaft was removed from the truck because we didn't have any way to hold it given that the torque value for the nut was 160-220 foot pounds. Bill headed to FLAPS and came back with a 1/2" drive 1 1/2" socket. I crawled under (3/4 ton truck with 31" tires has enough room for even my 295 pound body without raising the truck), pulled the cotter pin and tried to loosen the nut. No luck. Engine turned. We removed the flywheel cover and Bill stuck a pry bar in into the flywheel teeth to prevent the engine from turning. I got on the 1/2" drive 18" breaker bar/1 1/2" socket combination and gave it my all. No move. Scratched my head for a while and the Bill came up with a brilliant idea. Bill rolled a floor jack under the truck and positioned the lifting point on the jack under the end of the handle of the breaker bar. I went back to the flywheel to make sure the pry bar stayed in place. Bill started raising the jack. After a few false starts and Bill commenting how far the breaker bar was bowed, there was a loud pop and the nut came loose. Once we took a look at the piece of the breaker bar that the socket mounts on we found that it had twisted about 10 degrees. No telling how much torque it took to break the nut loose, but it was WAY north of the 160 pound minimum. No way we could have broken the nut loose on the bench per maintenance manual instructions. Once we broke the nut loose the rest of the job went pretty much by the book. Disassembled and cleaned up the parts. Shot some paint on the outside parts. It was a bit of a trick getting the seal out of the rear end of the tube. We didn't have a seal puller. We could reach through the tube with various pipe-type implements, but they all wanted to slide through the seal instead of catching an edge and driving the seal out. Bill came up with another great idea. He took a length of 1/2" rebar and bent a 1" dog leg into one end. This allowed it to catch on the metal of the seal and when the other end was tapped with a hammer out came the seal. By the way, the GM part number 3869176 seal crosses to SKF 14875 which my NAPA store had in stock! The old seal was a National 1-35. We used a 2" PVC pipe coupling as a driver to knock the new seal into place. The bearing at the rear of the front shaft was in good shape, so we did not replace it. Just in case you need to know it is a New Departure X 88107. Was used on GM, Ford, Isuzu, International and Dodge truck products until at least the year 2001. 1980-1994 Alfa Romeo Spyders used them as rear wheel bearings. The 3/4 ton front U joint (inside the ball) is completely different (much heavier) than the front U joint in a 1/2 ton model. No parts interchange at all.
Good pictures Bill. Had a good time working with Bill Hanlon. Easy going, and trainable.. Only problem was that I couldn't get him to let me paint anything Yellow!
By the way Bill, we guessed right about the orientation of the hangar. We could have verified it if my old semi-busted camera would "play back" pictures.
Great documentation!!! Thank you for taking your time to document this as well as you did! (Your usual attention to detail~) That bit about your struggle with, and solution to, the stubborn nut will help everyone who does this procedure! No more leaks I hope?
