Torque Tube Bushing Replacement
By Stephen Kassis
Early Chevrolet cars & ½ ton trucks (1925-1954) driveshafts use a torque tube with a propeller shaft instead of an open driveshaft that was used after 1955. This design worked to stabilize the rear axle and hold the propeller shaft that is inside the tube. If properly maintained, the bushing in the front of the tube will last many thousands of miles. However, the gear oil which lubricates the U-joint and driveshaft bushing will often leak due to bad seals, causing the bushing to run dry. Failure of this bushing will cause a vibration in the propeller shaft and may even cause the U-joint to fail. The first part of this article will discuss the procedure to replace the torque tube bushing on a 1930-33 passenger car. The procedure is similar on all bushings that were held in with dowel pins, up through 1950.
These bushings can be replaced in the vehicle or on the workbench. Though it is easier to do with the propeller shaft removed, it is not absolutely necessary. The first step is to disconnect the torque tube from the transmission. Be sure to support the tube with a floor jack because there is a lot of downward pressure on the tube. Remove the four-bolt collar at the back of the transmission. Put a drip pan below the rear of the transmission to catch dripping gear oil. Slide the ball housing and collar back as far as possible onto the torque tube. Disassemble the U-joint and drop the torque tube down below the transmission. (Brake cross shafts & parking brake cables may need to be removed to lower the torque tube.) Remove the rear U-joint yoke and slide the ball housing and collar off of the tube. Wipe down the outer tube housing with solvent and dry it off (Fig. 1). Note that the dowel pin that holds the bushing in place is at the top of the tube, just behind the slot.
Drill out the dowel pin (Fig. 2) but be cautious not to drill too deep as you may damage the propeller shaft. Once the pin is out, drive the bushing forward and out of the tube (Fig. 3 & Fig. 4). Down inside the tube is a cork seal that is most likely very deteriorated, if it is there at all. Directly behind the seal is a flat metal washer (Fig. 5). If you are working with the propeller shaft in place, use a long skinny screwdriver to break up the remainder of the cork gasket. Compressed air will blow the fragments out of the tube. Be sure to get the inside of the tube completely clean in order to get a good installation of the new bushing and seal. If the propeller shaft has been removed from the tube, you can use a hooked tool to remove the flat washer (Fig. 6). Clean the inside of the tube of all residue.
Run a finger carefully over the splines of the propeller shaft. If you can feel raised, sharp edges, use a flat file to dress the edges and smooth them out (Fig. 7). This will prevent sharp edges on the propeller shaft from damaging the bushing or seal when they are installed.
The order in which to install the new bushing and seal (Fig. 8) is very important. Start with the clean flat washer, next to the washer is the seal. Coat one side of the washer with grease before insertion and stick it to the flat surface of the seal. Play close attention to the direction the seal is put into the tube (Fig. 9). The working surface of the seal is the one with the spring and this is always faced toward the oil. In this case, it should be facing forward. The purpose of this seal is to prevent gear oil from leaking down to the differential and leaving the U-joint without lubrication. Lubricate the seal on the outside and inside surfaces and insert into the tube.
Finally, lubricate the inner surface of the bushing with gear oil or grease and install it with the exterior groove toward the front of the tube. Tap it back into the tube with a punch until a dull thud is heard. This will indicate that the washer is seated against the ridge inside the tube. Compare to Fig. 1 to see if your bushing is seated properly.
Once the bushing and seal are properly seated it is time to drill a hole in the bushing to accommodate the new dowel pin (AF-367). It is important that the top of the dowel is below the surface of the tube so the ball housing will slide over it. Once the dowel is seated below the surface, use a centering punch in several spots on the edge of the hole. This will lock the dowel in place and keep the bushing from rotating.
Replacement bushings for 1937-1954 passenger & ½ ton models (V-10*) come complete with a seal and two bushings in a single unit. These are commonly referred to as Oakie bushings and are much easier to install. The original seal and rear bushing will not need to be removed. Only the front bushing must be removed. Replacement bushing and seal assemblies are press fit and do not require a dowel pin to install. This assembly is installed at the front edge of the tube in front of the old rear bushing and seal. From 1951 to 1954 the bushings were pressed in place and the dowel pin of the earlier years was eliminated.
For the 1951-1954 later style original press fit bushings, there is a special puller (V-100) that will pull the front bushing out without removing the propeller shaft. This tool can also be used on the earlier bushings but the dowel pin must still be removed first when using this puller, caution must be taken as the steel backed bushings may separate allowing the bronze insert to come out of the steel shell. If this happens, simply try using the tool a second time. It should grab the steel backing and pull it out. The steel backing must be removed in order to install the new bushing.
Be sure to check the propeller shaft for sharp edges and file to smooth them if necessary. Lubricate the inner surfaces of the new bushing and seal assembly, including the seal. Start the assembly into the tube with the seal end first. Use a block of hardwood and a large hammer to pound the assembly into place. Do Not strike the new bushing directly with a hammer as this may damage the bushing. The new assembly should install nearly flush to the end of the tube.
There is a special procedure to adjust the U-joint ball housing. Using a new gasket set for the U-joint housing (FS-125), take all of the 4-bolt gaskets (shims) and bolt the retaining collar and ball housing onto the back of the transmission. For this adjustment, do not use the gasket in the back of the collar. With a rubber mallet, strike the back of the ball housing to see if it moves easily. If it moves without much effort, take one of the shims out and tighten the collar. Test again until the housing can just barely be moved. If it is too tight, it will cause the U-joint to bind, causing damage to the U-joint or driveshaft bushings. If it is too loose, it will cause leaking.
Once the ball housing has been adjusted, install a new tapered gasket at the back of the retaining collar. Lubricate the working surface of the gasket with grease. Grease the outer surface of the torque tube where the ball housing will install. Install new gasket at the back of the ball housing and coat it with grease. NOTE: 1925-1933 models have a fixed cork seal at the back of the ball housing. This is replaced with a neoprene O-ring (FS-4356). Dig out the old cork with a screwdriver. There should be two flat steel washers that cannot be removed. Clean out the cork and grease up the seal, pushing it between the two washers.
If you have a screw-on seal at the back of the ball housing, install the rear seal between the two original flat washers followed by the screw-on collar. Lubricate the inside seal surface. Slide the collar over the ball housing and both pieces onto the tube. Hang the shims over the ball housing. Install the U-joint and bolt up the ball housing, collar and shims to the back of the transmission.
CAUTION: Once the &-joint and ball housing are installed, it is vital that gear oil is filled before operation. DO NOT USE GREASE! THIS HOUSING MUST BE LUBRICATED WITH GEAR OIL. 1925-1936 models should use 600W gear oil (VT-40) to prevent leaking and damage to the bronze bushings in the transmission & differential. Consult your shop manual for the proper gear oil for your specific vehicle. Check and fill the transmission with gear oil. The ball housing has its own fill plug at the top of the back of the transmission housing. If there is no plug on top, some transmissions have to be filled through the speedometer drive gear hole. About ½ pint of gear oil will be required to lubricate the U-joint.