64 Steering Knuckle ??

[Gary D.]

Is there any difference in the R & L knuckle? They look the same but have two different #'s on. One is GM141D which I think is R and the other has GM139D which I think is L. Thank You for all help Gary

[Joe L.]

Re: 64 Steering Knuckle ??

Gary-----

There is no difference between the left and right steering knuckles for any 63-64 Corvette (for that matter, there's no difference between the left and right for 65-67, 68, or 69-82, either). The numbers that you mention are forging numbers and denote the particular tooling used to produce the part. Rarely will you find 2 parts on the same car with the same forging numbers; it can happen but it's more coincidence than plan. Your steering knucles should have the forging number "3828580" on them somewhere. It may be lightly embossed and, therefore, difficult to see. These embossments are seen as "raised" characters on these pieces.

Also, while the KNUCKLES are the same for either side, the STEERING ARMS are NOT the same for either side. The steering arms are attached to the knuckles with two 7/16-20 bolts for all 1963-67 Corvettes.

[William Liddle]

Re: 64 Steering Knuckle ??

Joe, if the numbers that Gary refers to represent the tooling used to make the part and the parts are identical, why would the numbers be different? I would think that they would be produced using the same tools.

[Joe L.]

Re: 64 Steering Knuckle ??

William-----

The tooling is "identical". However, there are more than 1 set used for the manufacture of many parts. For some parts, only 1 set of tooling may have been used. However, for parts like steering knuckles, there were probably 2 or more sets of forging dies.

The same thing is true for most cast parts. For example, you will note that cylinder blocks, cylinder heads, intake manifolds, etc. of any given casting number will also have other markings on the part. Things like "GM10", "GM25", or "GMT17". These marks identify the particular set of tooling used to make the part.

[Joe L.]

Addendum

Also, cast parts which have a tooling number prefix of "GMT" means the part was cast at the old Tonawanda Foundry (closed in 1984). Forged parts with the tooling number prefix "GMT" indicate a part forged at the old Tonawanda Forge (not too far from the old foundry and now owned by American Axle and Manufacturing).

Apparently, the 1964 steering knuckles that Gary has were not manufactured at Tonawanda, though. Based upon the numbers he reported, I suspect that they were probably forged at the old GM Detroit Forging plant (the only other forging operation which GM had at the time and now also part of American Axle and Manufacturing) on Holbrook Avenue in Detroit (now Dauch Drive). I don't know that the number indicates the Detroit plant, though. It's also possible that they were forged at some outside supplier using GM tooling.

[William Liddle]

Re: 64 Steering Knuckle ??

Joe, what you said about multiple sets of tools being used to provide a given part is correct but for a forecast forging run of 50,000 parts it would be normal to expect 2,000-5,000 parts from one set of tools, depending on which forging process is being used, presses or hammers. I just thought it was unusual that identical #'s wouldn't normally be found on one car. Customers specify their stamping identification on the blueprint and little of it changes during the course of forging a product. Most will require their pt.#, which rarely changes, die set # which will change when the tools are changed and the lot or heat code designation, which will change every time a new lot of steel is introduced. This doesn't happen often if the steel is ordered in an adequate quantity to fill the order. I've never followed forgings after they left the plant but would have thought that two forgings on the same car with the same numbers might happen more often.

[William Liddle]

Re: Addendum

In the 1960s and 70s we did a lot of work for GM but mostly their Electromotive Division. We supplied all of the tooling but would mark it per their requirements. Parts produced from our tools would probably have been identical to parts produced at other plants contracting to GM or from the GM forging plants. The only difference would have been in the die identification and lot #s.

[Joe L.]

Re: 64 Steering Knuckle ??

Bill-----

I agree with you. For Corvette-specific parts, it's always surprised me that there were as many sets of tooling as I see represented by these numbers. On my 1969, the original front spindles have different tooling numbers. Also, every other forged part on the car which has tooling numbers on them and for which there are 2 or more used on the car have different numbers.

Another factor may be that while a certain number of parts might be expected from a single set of tools, perhaps GM used multiple sets at the same time rather than one set to end-of-service life, followed by another new set. I agree that it would seem strange that they would have seen the need to use more than one set at a time. It seems like they ought to be able to keep up with Corvette spindle requirements, both PRODUCTION and SERVICE, with just one set of tools on one shift.

However, maybe there are more cars than I think that have "matching forging numbers". Anyone else out there have anything to offer on this subject based upon observations?

[Joe L.]

Addendum

Bill-------

One other thing that comes to mind as I thought about it is Corvette rear bearing supports. These are a nodular iron casting. Every one has a mold or pattern number on it. The original ones on my car have different mold/pattern numbers on them. although these are castings and not forgings, I have made a "mini-study" of these on cars. So far, I've never seen a car that had the same mold/pattern number on both sides. Looking at these things at swap meets, there are a plethora of different numbers. Presumably, each different number represents a different mold or pattern used for its casting. It's always absolutely baffled me that there would be more than a few mold/pattern numbers used for this part. The exact same number of these are required to be manufactured during Corvette PRODUCTION as front steering knuckles. Why in the world were all of these mold/patterns required?

[William Liddle]

Re: Addendum

Joe, its beyond me why so many molds would be required. I've been involved in the forging business since 1967 and have worked right next door to a major Chicago foundry all of those years but have never been inside or gotten involved with the casting business. In the old days we did work for everyone from Harley Davidson to Boeing Aircraft and were a very diversified plant which is probably the reason we survived when a lot of forging plants didn't. I do recall that some casting processes require the mold to be broken for each part produced which doesn't sound like a money making procedure.