Early U-Joint Assembly Tool (1928-1939)
By Stephen Kassis
Early Chevrolet passenger car & 1/2 ton U-joints are held together with two round plates bolted together around the pivot balls of the U-joint trunnion. When reassembling this type of U-joint, a special tool is available to assist in this procedure (FS-9580).
The front plate of the U-joint has four studs fixed into it. This plate fits over the round pivot balls, locking them into the recesses of the front & rear plates. Holding the front plate steady while assembling the U-joint is a challenge and the main reason for this tool.
Before assembly, it is a great opportunity to check the condition of the driveshaft bushing. This bushing sits inside the front of the torque tube and is held in place by a dowel pin. Early vehicles have only one bushing but 1934 & newer vehicles have two bushings, one to hold the driveshaft and one to steady the front yoke of the U-joint. If these bushings are bad it can cause vibration when driving and also damage the oil seal, which sits behind the bushings. To check the driveshaft bushing, grab the splines of the propeller shaft within the torque tube. If you can move the shaft up and down without moving the outer tube, the bushing(s) should be replaced. If needed, both the bushing(s) and seal should be replaced before assembling the U-joint. (See separate installation instructions that come with torque tube bushings.)
The first step in reassembling the U-joint is to check the ball housing gaskets. These gaskets (FS-125) must be installed prior to assembling the U-joint. New gaskets are always recommended. If these gaskets are not fresh, leaks may occur. It is important to adjust the gaskets on the ball housing to achieve proper sealing. The U-joint gasket set consists of 4-5 adjusting shims, large collar gasket and small rear housing gasket. Install the metal collar, without the collar gasket onto the ball housing. Put in 3 or 4 adjusting shim gaskets (with four holes) and tighten down the collar onto the ball housing. Check that it is a tight fit but not binding. A good test is to hit the rear of the ball housing solidly (not a full swing) with a rubber mallet. If the housing will not move, add a shim. If it is too loose, remove a shim. The housing should barely move when struck solidly with a rubber mallet.
On early vehicles, prior to 1933, the rear of the ball housing has a permanently fixed cork gasket at the rear. It has two metal washers with a cork gasket in between. To replace this gasket, dig out the old cork with a small screwdriver and blow out with compressed air. Lubricate a #327 (FS-4356) neoprene O-ring with grease and push it in between the two washers. For later models, the ball housing has a screw-on flange which allows for easy gasket replacement. Lubricate the outer housing of the torque tube with a light coating of grease. Once the gaskets are adjusted properly, install the collar gasket and coat the gasket operating surface with a thin film of grease. Slide the collar over the ball housing and push the assembly onto the greased torque tube. Temporarily hang the shim gaskets on the ball housing as they cannot be added after the U-joint is assembled.
Check that the balls are installed on the trunnion properly. Each ball has a flat side and a recessed side. The flat side should be faced outward on each stud. This will leave the recessed side facing inward. The orientation of these balls is important for proper lubrication of the trunnion. With the balls installed properly, seat the stud plate against the two balls of the front yoke and hold temporarily while installing the tool.
Slide the forks of the tool (FS-9580) behind the stud plate. Center the tool at the end of one of the trunnion arms and tighten the thumb nut. This should bring the stud plate up snugly against the U-joint pivot balls. This will also position the four studs in the plate so they are facing outward. Install the outer ring over the rear yoke and balls of the U-joint and assemble lock washers and nuts. Be sure the transmission is in gear so the U-joint will not turn. Snug down the nuts to hold the plate in place. Check that all of the balls are seated properly in the plate recesses. To tighten all nuts may require turning the U-joint. If this is necessary, put the transmission into neutral, loosen the thumb nut and rotate the assembly without removing the tool. Re-tighten the thumb nut and finish tightening the nuts. Remove the installation tool, put transmission in gear and torque the four nuts to 8-10 foot pounds.
Slide the ball housing and collar forward into the back of the transmission housing. Assemble the ball housing and collar assembly onto the back of the transmission and tighten the four bolts with lock washers. The final step is to add about 1/2 pint of gear oil (same type as is required for the transmission) into the ball housing. Consult your shop manual for the proper type of gear oil for your vehicle. Note: 1936 and earlier cars & truck use a special gear oil – 600W or 160W mineral oil (VT-40). This is not an oil that can be found at most auto parts stores. This oil has no additives that will attack bronze. Using modern gear oils can damage the bronze bushings in early transmissions & differentials.
On early transmissions, there is a fill plug at the top of the ball housing at the rear. If there is no fill plug, it will be necessary to remove the speedometer drive gear to fill the U-joint housing with gear oil. IMPORTANT: DO NOT use grease to lubricate this U-joint. This assembly requires gear oil and using grease will eventually cause driveshaft bushing or u-joint failure.