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Posts Tagged ‘rear axle’

Rear Axle Bumper Change

Wednesday, August 29th, 2012

Before 1954 on 1/2 tons, the frame rails were given a large arch as they passed over the rear axle housing. With a broken leaf spring or overloading the bed with too much weight, the frame rails will lower many inches before contacting an axle bumper. It was a system that worked for over 20 years on 1/2 tons when the frame rails were forced down toward the rear axle. A hard rubber axle bumper was placed under the hump in the frame to prevent metal to metal contact when this occurred.

For 1954 a totally redesigned pickup bed resulted in a three inch increased depth of the bed for more load volume. Some of this increase required a lower arch in the frame rail over the axle. There would be less space here so the rubber axle bumper was changed in length and was moved to the side of the frame. See photo!

Therefore, this prevents a correct interchange between the 1949-53 1/2 ton frame and the 1954 and newer frame. If this is done the beds will not have the correct relationship to the height of the cab.


1954 to 1965

1947 to 1953

1954 to 1955

1954 to 1955

Rear Axle Bumpers

Thursday, February 11th, 2010

The placement of rear axle bumpers by GM on 1/2 tons proved to be an important feature. Owners can often load cargo over recommended weights, their shock absorbers may lose their resistance, and there is the existence of uneven road surfaces. All this can make axle bumpers very important.

During the hauling of freight, these bumpers occasionally stop metal to metal contact between the frame rails and the axle housing. GM placed them just above the rear axle.
See photos.

rear axle bumper

1947-1953 1/2 ton (above)

In 1954 GM increased the depth of the 1/2 ton pickup bed from 15″ to 18″. To do this they lowered the frame rail arch above the rear axle. This shortage of space caused the bumper to be placed at the side of the frame but still above the axle.

rear axle bumper

1954 1/2 ton (above)

Early Rear Axle Bumper

Thursday, February 11th, 2010

Mechanical components on trucks were usually kept for many years by GM. Unless an improvement was needed, there was no need to change a proven design.

early axle 1

An excellent example of this is the rear ½ ton axle bumper. The design was used from 1929 through 1946 on Chevrolet and GMC ½ tons. A rubber bumper is held down on the rear axle housing by a metal cover with two ears. These ears are firmly secured by the two u-bolts that connect the leaf spring to the round axle housing. If the truck is overloaded or the shock absorbers are worn, the rubber bumper prevents metal to metal contact between the axle and frame rail.

Two of the attached photos show an original used retainer with bumper in place. The black bumper (now reproduced) is how the rubber part looks when new.

early axle 2

early axle 3

early axle 4

early axle 5