Early Cars & Trucks Rear Axle (Part of the series: “More than you ever wanted to know”)

By Tim Palmer and Gary Baxter

The purposes of this article are: To document what we think we know. Much of what is in this is either not in any of the recent books or not in much detail. To provide interchangeability information. To provide some tips on maintenance and wear. The information comes from GM parts books and our personal Corvair parts collections. The Part names are names given in the GM parts books and shop manuals. The Group X.XXX is GM’s method of grouping part(s) in their parts books. The Part numbers are GM part numbers unless otherwise noted.

The upper axle in this picture is for trucks (also known as forward controls or FC’s for short). The lower axle is for cars.

Notes:

1. This part was painted chassis black we believe.
2. The FC axle is longer, is larger in diameter and has five wheel lug studs.
3. Look for wear and signs of corrosion on the splines. The splines should be square looking. If they are rounded or pointy, look for another axle. Put your best one on the right side since it takes most of the load.
4. The bearing assembly is pressed on and requires either a press with a proper fixture or special puller to remove. Clark’s has the proper tools.
5. Contrary to rumors spread by some, the axles are NOT right and left. |

Notes:

1. Look for wear and signs of corrosion on the threads. You can find replacement studs at a good auto parts store or from the Corvair vendors.

Notes:

1. The two different part numbers are curious. We have not been able to determine the difference. The flange and the yokes didn’t change.
2. This is a common part used on many GM vehicles. It’s available at most any part store.

Notes:

1. This part wasn’t painted.
2. The splines on the flange are the weakest part of the rear axle system. Look for wear and signs of corrosion on the splines. Red dust as shown below is a bad sign. The splines should be square looking. If they are rounded or pointy, look for another flange. Put your best one on the right side since it takes most of the load. If the splines fail there will be a loud awful grinding noise and you will not be going anywhere!
3. The flange is fairly tight fit and should require a puller to remove. If it falls off when you remove the axle bolt, you should look at the flange and the axle to see which one or if both are worn and/or corroded to point you need replace them.
4. When the axle is installed in the vehicle you should be able to pull on the axle as hard as you want and not see any movement between the flange and axle. When the flange is on the axle there should not be any movement at all! If you see a little puff of red dust when you pull on the axle you should check and replace parts as needed. You are on borrowed time before the spline fails. It’s usually the flange that fails.

Early signs of rust and possible failure.

Notes:

1. This part wasn’t painted.
2. Check the splines for wear on this part also.
3. The splines should be square not pointy! The positraction yoke does not show up in any of my parts books! It does sort of show up in the assembly manuals. If you use a regular yoke, it will rub on the positraction differential side adjuster.

1960 Car 1^st Design

Notes:

1. The 1960-62 fit 1963-64 but 1963-64 do not fit 1960-62. This is because the axle hole in the A-arm got bigger in 1963.
2. Car bearings also fit a few years of Pontiac Tempest.
3. FC bearings fit nothing else!
4. NOS bearings have been expensive for some time, especially FC’s, so it is a good idea to keep the bearings greased as has already been documented.
5. While aftermarket bearings were available in the day, only recently have newly manufactured replacement bearings been made available in two types.
   1. The first type is a new bearing and aluminum housing. If you chose this type you should be aware that the aluminum housing is thicker than the original housing and only leaves 3 or 4 threads left on the stud for the lock washer and nut. The bearing comes with new self-locking grade 8 nuts (the self-locking nut eliminates the need for the lock washer and therefore the space for it), but I would strongly recommend installing longer studs because I don’t believe the original stud was grade 8. This is important because that nut and lock washer are all that keeps the axle from becoming detached from the rear a-arm when you are driving aggressively.
   2. The second type is a new bearing that fits in your old housing. This is so new I haven’t seen one yet. It sounds like a really good solution that fits just like the original and the price is competitive with NOS. |

Notes:

1. The 1960 has an arrangement completely different than the later years. The deflector is mounted backward from later ones. The shield is mounted to the A-arm instead of the bearing. (Sorry no picture of the shield). The 1960 and 1961 Shop Manuals show this arrangement even though it changed to the later arrangement in 1961 and maybe sooner.
2. The Chevrolet Service News indicated there was a first design 1961 FC and 2^nd design although the parts book doesn’t show anything.