The closed drive shaft ( on GM 1/2 ton, 1937-54) is supported at the front by two bushings. As these wear egg shaped over many miles, the drive shaft begins to move up and down. This ruins the grease seal and causes the u-joint to begin rubbing the “bell” that covers it. Thus noise and vibration!
Finally, with a bad seal, the rear differential fills with transmission grease running down the drive shaft torque tube, starving the shifting gears. The rear wheel seals then leak, the brake shoes become oil soaked, grease runs down the inside of the tires and finally the bell flies apart from rubbing the u-joint.
Catch the developing problem early and save much expense and down time. Install what is sometimes called an “Okie Bushing”, an aftermarket, produced originally in Oklahoma. This is a non-GM repair used successfully since the 1960’s. This is a quick, permanent fix that does not require tearing down the differential or driveshaft!
Remove the u-joint bell retainer and slide the aluminum round bell back, exposing the u-joint assembly. Disassemble the u-joint by removing the four bolts. The rear u-joint yolk can now be slid off the 17 drive shaft splines, exposing the front bushing.
Pull out this front egg shaped bushing from the torque tube. The 1939 to mid-1950 bushing is held in place by 2 dowel pins. These must be pulled out to remove the bushing. On occasion this bushing will require a puller. On late 1950-54 the bushing was slightly enlarged to be a press fit. This will require a bushing puller. Special pullers can be rented. Otherwise, call Jim Carter’s Truck Parts at (800) 842-1913. They have these pullers made.
Press in the long Okie bushing – seal first. Placing a wood block over the bushing end and tap into the drive shaft housing (torque tube) with a hammer. This action will then press the other original rear bushing and seal back out of position. The new Okie bushing will now hold the drive shaft in perfect alignment, as when the vehicle was new.
The original factory advertised this as a permanent one hour fix. This timing is optimistic but so much easier than disassembling the differential and drive shaft as the Chevrolet dealers did 50 years ago.
Okie Bushing Trivia
The almost bullet proof enclosed drive shaft system on 1937-1954 Chevrolet / GMC ½ tons and passenger cars (GM knew what they were doing) does have one weakness that surfaces on some vehicles, particularly after 60 years of driving.
What was once a major repair job has now been shortened to a few hours in your home garage for those with limited equipment and basic mechanical know how.
Introduced in the early 1960’s, this non-GM repair part has saved so many vehicles from being sent to the salvage yard! The genius inventor was in Oklahoma and thus, his creation is called an OKIE BUSHING.
HERE’S WHAT HAPPENS: After many, many miles the two large bushings that support the enclosed drive-shaft at its front end beside the transmission, may begin to change from round to egg shape. The hidden rear u-joint yolk that slides over the splines in the drive-shaft end, begin to cause an egg shape in the top of the bushing from the years of driving.
The more the ½ ton or car is driven, the more the two bushings can become “out of round”. The seal can no longer hold back the transmission lubricating grease. The grease slowly moves down the drive-shaft closed torque tube to the differential.
RESULTS: The differential housing fills with grease beyond its capacity and this fluid begins filling the two axle housing. Next event! The wheel seals beside the rear backing plates begin to leak. The brake shoes become grease soaked (no longer have friction to help stop the vehicle) and only front brakes exist. The grease then slowly runs down the inside of the rear tires and also collects quantities of road dust.
Oh yes, the other sad thing is occurring! This flowing grease that has come out of the transmission and was needed to lubricate its parts. Sooner or later, the gears and bearings here will be permanently damaged. You now have a ½ ton pickup or car ready for its last days!
HOW TO KNOW THIS IS COMING! When you let up on the gas pedal while on the road, you will probably begin to hear an ungodly roar but the vehicle just keeps going. This is what is happening: After the rear u-joint yolk has allowed the grease seal to leak, the total joint assembly starts to rub the aluminum round bell that surrounds it. This bell is so close to the turning u-joint, it takes little bushing egg shape wear to start the rubbing with noise effects. By this time all the above is happening and it is the sound that tells the driver that the end is near! If you suspect trouble is coming, here is an easy way to diagnose if it is close to the time you will start walking: Remove your differential add-oil plug. If oil comes out, the transmission is starving and your rear tires will soon be grease covered. Do not drive this pickup beyond your garage. The more you drive it at this point, the more parts you will need to replace.
Facts You Should Know
From 1937 through 1950, GM secured the original front torque tube bushing with two very small dowel pins. This was to be sure the bushing did not seize on the rotating drive-shaft, and thus, would spin on the inside of the torque tube housing. If this occurred the long term results would be a disaster! Transmission gear oil would soon begin to seep down the torque tube to the differential as the tube begins to increase in an inside diameter. The results: It would be the last Chevrolet car or ½ ton the unhappy owner would ever own!
To safeguard this from happening GM added the two dowel pins as insurance against this bushing ever spinning inside the torque tube.
A CHANGE IN 1951-1954: GM increased the diameter of the front torque tube bushing to make it a tight “press fit”. The dowel pins were then not necessary or used.
With this “press fit” in 1951-54, a bushing puller will be required! Even after the two dowel pins removed on the 1937-50, there will be some front bushings that will still require this puller!
To remove a stubborn dowel pin, some drill a hole part way into the center, screw a fastener in place, and then pull on the screw to remove it. Then, the larger bushing can be removed.
IMPORTANT SUMMARY: The GM closed drive-shaft system is not second rate quality! So many 60 year old ½ ton pickups are still using this system after 60 years with no attention. The later open drive-shaft replacement does not have a record even close to this. They are just easier to replace when a problem occurs.