VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 1940 1/2 ton rear spring seat

How much clearance is there between the spring seat on a 1940 1/2 ton and the rear axle.
The manual indicates that it is tight.
I can pass the front of a screwdriver between mine.
Should their be a spacer?
Can I make a shim to close up the gap?

The space seems to large to be due to just wear....

The spring seat does not appear to be warn badly.

Thanks,

Mike

I dont know the correct specifications but I would consider that to be excessive. When I put my 38 back together I made a packing piece (may not be the recommended method) allowing a grease passage.
Tony

Mike,

My guess Is that the clearance when new was probably between .005 and .010. Because the upper half of the spring seat carries the weight of the back end of the truck, the bulk of the wear in the spring seats is in the upper half and on the top of the axle housing. On one of the 1940 pickups I had, due apparently from never being greased, the upper spring seat had sawed its way almost through the upper half of the axle housing.

The shop manual indicates that in repairing a worn spring seat, file the mating surfaces of the two spring seat halves until you have a close slip fit when the spring seat is assembled on the axle. In your case, it appears that would take a huge amount of filing. Probably better to have a machine shop mill the required amount off. The problem you'll most likely have is that both the axle housing and the spring seat bore are no longer round. In fact, they're probably tapered as well as oblong, so figuring out how much to machine off can be a challenge. Because almost all the wear occurs on the upper half of the spring seat, by milling most of the required amount off the upper half, you will bring the bore of the spring seat assembly back closer to round. It would probably be a good idea to leave the bore a little tight, then reassemble the spring seat halves with a few thin shims between the halves to allow for adjustment for future wear, much the way main and rod bearings are adjusted. Assuming you have the front end of the drive shaft down, after assembling the rear spring seats to the axle housing and tightening the leaf spring U-bolts, make sure that the rear axle rotates freely within spring seats, or with only a slight drag.

A note on greasing the spring seat bearings. Place a jack directly under the middle of the leaf spring and jack the truck up till the tire leaves the ground. This will open the clearance between the upper spring seat and the top of the axle housing where the grease is needed. Inject grease till you see it come out the sides of the spring seat. Then set the truck down and remove the jack. This will shift the clearance to the lower half of the spring seat. Inject some more grease into the spring seat.

For the beginner, if you're working on your rear leaf springs, shackles or spring seats, and you have not disassembled the front U-joint and lowered the torque tube, be careful on how low you lower the rear axle. With the front U-joint and ball housing made up, there is a limited amount of up and down movement of the torque tube. Depending on how high you have lifted and supported the rear frame, and if you have the rear wheels removed, it's possible to lower the rear axle low enough so that the front of the torque tube fetches up on the bottom of the ball housing, causing it to bear the full weight of the rear axle, multiplied by the leverage of the torque tube length. I once looked at a 39 1/2 ton for sale and noticed that someone had installed a lowering kit on the rear end. I also noted a big chunk of transmission case broken off at the bottom of the ball housing. The seller didn't say what happened to the transmission case, but I had a pretty good idea.

Mark

I agree with Mark that due to the amount of wear that is indicated you need to carefully evaluate the axle housing in the area of the top half of the spring seat. Remember that even thought there might be a difference in hardness of the 2 metals in a moving joint, there will be wear on both surfaces. Obviously the softer surface will wear more, but they do both wear.

I also completely agree that you need to make sure you get grease to that portion of the connection. His method works or you can use the approach I use.

Whenever I grease my car I set the frame on jackstands and the axles hang in the dropped position with the wheels still off the ground. On the rear that allows grease to get to the upper part of the spring seat. In the front it lets the grease go to the normally loaded side of the kingpins. For both axles it also lets grease go the normally loaded side of the threaded shackle pivot pins.

I picked up on this technique in a post a few years ago from Gene.

To deal with the wear on the Spring seat and rear axle housing, I cut down both faces of the spring clamp so as to make a relative snug fit on the axle housing. There is a reference to that in the shop manual for a1940 Chevy 1/2 ton.

That seems to work but I am concerned about the wear on the axle housing.

I don’t know how thick the housing is and what concerns I should have about the wear.

The warn axle housing measures about 2.635 vertical and 2.685 across at the spring seat location.

I have access to a rear axle of of a 1941 car. Would that be a suitable replacement?

Thanks,

Mike