Through 1954

Chevrolet half-ton pickups and passenger cars used a “closed drive shaft system” that connected the transmission with their differential.

Despite many negative comments in today’s world, it was a very successful system considering the roads that were available and the slow speeds (by today’s standards) that carried Americans from place to place.

It is referred to as a “closed” drive shaft because the long moving shaft that transfers the power from the engine to the differential is covered by an enclosed torque tube. No dirt ever gets inside!

Millions of the vehicles mentioned above were sold each year. If this were not a good system, there would have been changes made long before they were replaced by the “open drive line” in the mid 1950’s.

So many other makes of vehicles used them. Even the 5 million 1928-31 Ford Model A’s were all equipped with a closed drive shaft system. (Currently, as many as 25% Model A’s exist with club chapters in all major U.S. cities. This does not reflect a weakness in the driveshaft.)

For Chevrolet ½ tons close driveshaft, there was one small link that later caused a major expense. After many, many miles, a noise sometimes develops in the front of the drive line. This was where the closed driveshaft met the U-joint on the back of the transmission. The noise always continues to increase! REASON: The two bearings on the front of the driveshaft are becoming egg-shaped. If ignored by the driver, (it usually is) then the oval seal from the transmission also becomes egg-shaped because the two driveshaft bearings behind it had taken on the same shape!

This is the beginning of a major expense! The transmission fluid is now free to slowly pass over to an egg shape seal. Of course, the only place for oil to run in the closed drive is back to the differential. When it is full, the two axel housings are there to carry the oil past their rear end seals. The next catch is the brake shoes! (Thus, no rear brakes) Now the driver looks at the rear. Oil has been running down the inside of the tires! Finally, the wearing was there for the driver to see!

By this time, the repair is really complicated. Most vehicle owners were at the mercy of a certified Chevrolet dealer.

The following is a closed drive shaft article written several years ago. More compliments on these closed drive shafts from many years ago.

Closed Drive Shafts

Occasionally, we hear owners condemning the closed drive shaft system used in the 1/2 ton trucks prior to 1955. After questioning the negative comment, we almost always discover the real criticism is the low gearing of the ring and pinion in the differential. Yes, this lower gear ratio was created more for slower roads of year gone by, but it is by far not a poorly designed system. In fact, it is questioned if there has ever been drive shaft and u-joint combinations that exceed the durability of this GM quality engineered closed unit.

Over 50% of the surviving older 1/2 ton pickups continue to use their original closed systems. Of these, the majority have had little or no servicing other than keeping lubrications in the transmission and differential.

Consider this when you realize the last GM closed drive shaft system was produced in 1954. Many others have been in irregular service prior to the 1920's. Also remember that many 1/2 ton pickups were often given abuse far in excess of the manufacturer's recommendations.

What modern open drive shaft system has been able to compare with this unsurpassed record? None!! Sure, the newer open u-joints are easier to change. They better be. They require attention or replacement so much more frequently!

Another Example of GM Quality!!!

We recently received the following comment from John Berkeley Ball. He also confirms the quality of the General Motor's 1/2 ton closed drive shaft and differential.

Dear Jim Carter

Thanks for your excellent articles. One very pertinent point I feel that you should mention about closed drive shafts is their absolute impervability to rear spring wind up. Used on the farm over soft ground with heavy loads, you could not afford to send your rear end into drive breaking pulsations every time you lost traction, whether the shocks were worn out or not (some were single action any way). What a huge advantage over the Hotchkiss rear end! this is an often unknown design attribute that Chevy engineers were unfoundedly maligned for - at least by today's city slickers...

John Ball

You may relate comments to this web site or Mr. Ball direct at john_ball@telus.net.