"As I dimly recall, the "drive" gear goes around the forward yoke on the 4-speed's u-joint?"You would be correct.
4 speed tranny Cross section pic It looks like drive gear is on the output shaft, but if you blow up the picture, the drive gear is really on the tail end of the Forward yoke.
I believe the speed-O drive gear is pressed on.
Don't forget
U-Joint Bolt Lock ClipsQ. Anything else worth replacing before reassembly .
Check for play in propeller shaft, wiggle it up down side to side.
If it moves, the propeller shaft bushing & oil seal are bad.
A quick fix is to install a Okie bushing sleeve.
The Okie bushing sleeve has the rear yoke bushing and the propeller shaft bushing & oil seal inside a sleeve.
1951 truck bushings are press fit, you will need a bushing puller to pull the front bushing out.
Then slide in the Okie bushing. You leave the existing propeller shaft bushing and oil seal in the torque tube.
(Check pictures below) .
At the rear of the U-joint ball housing there is a screw on retainer cap.
Inside the cap there is a oil seal sandwiched between two steel O-ring washers.
The oil seal dries out and it looses its tension which keeps the retainer cap from unscrewing itself and sealing.
Some oil seals are cork some are rubber. Replace with a Rubber oil seal and dress it with a thin film of grease before installing. The threads should be clean and dry.
To insure the rubber oil seal doesn't get cut-up, polish-up the front end of the torque tube with some emery cloth so it has a smooth surface to slide on. Do the same with the ball portion of U-joint ball housing. You want the ball collar cork oil seal to have a smooth surface to slide on. Lubricate cork oil seal with graphite grease before assembly.
Picture lower right corner of page (Also Check pictures below)
The four Universal Joint Ball (Housing) collar bolts, 8-12 ft. lbs. Torque.
The four Universal Joint bolts or cap screws, 25-30 ft.lbs. Torque
The one Universal Joint forward yoke attaching bolt, 15-20 ft. lbs. Torque
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