66 L36 Harmonic Balancer, Steering coupler

[John M.]

Re: 66 L36 Harmonic Balancer, Steering coupler

Jim,
Since the one that we have for the 66 is much longer on the steering wheel side than on the box side would it be safe to say that it's incorrect and that there is no difference between the standard and the tele according to original GM specs and drawings?
Thanks,
John

[Jim S.]

Re: 66 L36 Harmonic Balancer, Steering coupler

Within the Saginaw system there was a permit called a "Deviation." It allowed the manufacturing plant for a limited time to make a part out of the drawing tolerance(s) or change a process. At the end of a specified time either the plant had to get back to original specs or the drawing was to be changed. So it still is confusing to me that the telescoping flange assembly still has the paint note yet we know that most (if not all) of the service parts were not painted. Maybe it is just one of those things that just fell through the cracks.

Jim

[Joe L.]

Re: 66 L36 Harmonic Balancer, Steering coupler

I am back in Saginaw and have taken a look at the drawings.

Interesting stuff. The two assembly drawings were made in the early 1960s with very little change or revisions through the years.

The flange assembly (5690809) used on the 1965-66 Corvette with a standard (non-adjustable) steering column was originally released for production at Saginaw in late 1961. It always had a rubber coupling consisting of seven laminations of cotton cloth and neoprene. Production parts always had a brass ground strip. Service parts manufactured after February 1971 should have seven ply couplings (basically the same construction) with a screen ground.

Now some real interesting things with respect to the flange assembly (5692974) used on 1965-66 Corvettes with telescoping columns. The drawing was released for production at Saginaw in 1963. It has the same seven lamination neoprene/cotton coupling as above. There is only one revision to the assembly drawing and that was made in 1975. The revision was some minor changes to the flange that attached to the steering gear. The flange assembly was never revised to the screen ground coupling. There is note on the assembly drawing that this flange assembly is to be painted black! There is no such note on the flange assembly drawing for the standard column. From this assembly drawing you would expect all service parts for the telescoping column flange assembly to be painted black and also have a brass ground strip.

Jim

Jim-----


I was able to find one of the 2 NOS GM #5692974 couplings I have. Unfortunately, this is one that came to me without the GM packaging, so I don't really know, for sure, that it's a GM piece. The other one I have is in the GM packaging but I can't find it (of course, that's how it always happens; someday when I'm looking for something else, I'll find the coupling but not what I'm looking for at the time).

In any event, I believe this should show the GENERAL configuration of the 65-66 tele column coupler.


DSCN1076.jpg

DSCN1077.jpg

DSCN1078.jpg

[Jim S.]

Re: 66 L36 Harmonic Balancer, Steering coupler

Joe,
Your 5692974 flange assembly is close to my drawing. Not exact, but close enough to be functional in a 1965 - 1966 C2.

My 5692974 drawing was released for production on 9-17-1963 and there was only one revision made to the drawing (Rev A dated 2-21-1975). The revision documents a minor casting change to the bow tie flange that attaches to the steering gear input shaft. A small rib was added to the barrel of the flange. It shows quite clearly in your photo #13799. Since your part includes the rib your service flange assembly should have been manufactured sometime after 2-21-1975.

BTW the drawing has a notation "Inactive July 9, 1980". I think that the note means that Chevrolet indicated that they would no longer order service parts.

Now, here are the components that are different, your part versus the Saginaw drawing.

1. You have a 7 lamination coupling. I can count the cotton layers. Can you confirm that there is a screen on one of the coupling faces? I think that I can see the screen indentations in the red latex paint. I assume that there is a screen since there is no ground strip. A seven lamination coupling is correct.

2. Your assembly has two identical stop pins that are hot riveted in place. The length of your stop pins places the free ends something like 3/8 of an inch above the cutouts on the steering column flange. This 3/8 inch increased length was the standardized stop pin for flange assemblies used with energy absorbing steering columns with collapsible steering shafts. The Saginaw drawing has stop pins that are shorter and flush with the cutouts in the flange (reflecting the solid steering shafts used in the 1965 and 1966 C2s).

The stop pin that sticks through the pinch bolt side of the flange that attaches to the steering column is about 0.38 inch in diameter. The big difference is that the pin that sticks through the side opposite the pinch bolt is supposed to be 0.25 diameter. The flange assembly was designed such that the clearance from the stop pin diameter to the cutouts in the mating flange was to be about 0.12 inch.

I think that if you measure the width of the two window slots in the steering column flange, you will find that they are two different widths. The window width on the pinch bolt side of the flange should be about 0.62. The window width on the opposite side should measure 0.50. If you measure the clearances (window to pin) on your part that you will find that the clearance on the pinch bolt side will be around 0.12 but the clearance on the opposite side will only be something like 0.06 inch.

3. The blue paint dabs on the rivet heads indicate that they were visually inspected. I don't believe that paint dabbing started until the mid to late 1970s.

4. Obviously, no black paint on your service part. There is a paint note on my drawing.

Jim

[Joe L.]

Re: 66 L36 Harmonic Balancer, Steering coupler

Joe,
Your 5692974 flange assembly is close to my drawing. Not exact, but close enough to be functional in a 1965 - 1966 C2.

My 5692974 drawing was released for production on 9-17-1963 and there was only one revision made to the drawing (Rev A dated 2-21-1975). The revision documents a minor casting change to the bow tie flange that attaches to the steering gear input shaft. A small rib was added to the barrel of the flange. It shows quite clearly in your photo #13799. Since your part includes the rib your service flange assembly should have been manufactured sometime after 2-21-1975.

BTW the drawing has a notation "Inactive July 9, 1980". I think that the note means that Chevrolet indicated that they would no longer order service parts.

Now, here are the components that are different, your part versus the Saginaw drawing.

1. You have a 7 lamination coupling. I can count the cotton layers. Can you confirm that there is a screen on one of the coupling faces? I think that I can see the screen indentations in the red latex paint. I assume that there is a screen since there is no ground strip. A seven lamination coupling is correct.

2. Your assembly has two identical stop pins that are hot riveted in place. The length of your stop pins places the free ends something like 3/8 of an inch above the cutouts on the steering column flange. This 3/8 inch increased length was the standardized stop pin for flange assemblies used with energy absorbing steering columns with collapsible steering shafts. The Saginaw drawing has stop pins that are shorter and flush with the cutouts in the flange (reflecting the solid steering shafts used in the 1965 and 1966 C2s).

The stop pin that sticks through the pinch bolt side of the flange that attaches to the steering column is about 0.38 inch in diameter. The big difference is that the pin that sticks through the side opposite the pinch bolt is supposed to be 0.25 diameter. The flange assembly was designed such that the clearance from the stop pin diameter to the cutouts in the mating flange was to be about 0.12 inch.

I think that if you measure the width of the two window slots in the steering column flange, you will find that they are two different widths. The window width on the pinch bolt side of the flange should be about 0.62. The window width on the opposite side should measure 0.50. If you measure the clearances (window to pin) on your part that you will find that the clearance on the pinch bolt side will be around 0.12 but the clearance on the opposite side will only be something like 0.06 inch.

3. The blue paint dabs on the rivet heads indicate that they were visually inspected. I don't believe that paint dabbing started until the mid to late 1970s.

4. Obviously, no black paint on your service part. There is a paint note on my drawing.

Jim

Jim------


1) There is definitely a screen in the red layer of the coupling. I can even feel the sharp edge of it on the perimeter;

2) The stop pins are both the same and are 0.364" OD. They are 0.861" long as measured from the bottom of the flanged base to the top. The width of the window slot on the pinch-bolt side is 0.604"; the width of the slot on the other side is 0.515";

Other dimensions:

3.275"---overall length of the coupling from end-to-end

3.175"---maximum width of "bow-tie" flange (steering box side)

3.260"---maximum width of steering shaft flange

2.710"---minimum width of steering shaft flange

I show that the GM #5692974 coupling was discontinued from SERVICE without supercession in April, 1973. That's generally the date when the last one went "out-the-door" of the last GM warehouse stocking it. I also cross-checked this a bit with Corvette P&A Catalogs. The last edition I find the GM #5692974 in is the April, 1972 publish date. I would have expected it in the January, 1973 edition, but it's dropped out by that time. In any event, this more-or-less corroborates that it was out of the GMSPO system by sometime in early 1973. Perhaps, the 1980 notation of it being inactive is just when someone finally figured out that GMSPO was not ordering any more. The 1975 revision date is a real mystery, though.

[Jim S.]

Re: 66 L36 Harmonic Balancer, Steering coupler

I did find this bit of information today. The note on the Saginaw drawing "Inactive per 300,000 09JL80" means that the 5692974 Flange Assembly had not been ordered for service by the customer (in this case Chevrolet) for a minimum of five years. This note from the Saginaw Service Department informed the Saginaw manufacturing plant that it no longer needed to keep any special tooling in order to produce the part.

This 1980 Saginaw date is a seven years later than the April 1973 date that Joe Lucia found when Chevrolet discontinued the part for service without supercession. This fairly well fits the timeline of at least 5 years without any orders.

We still have the issue as to how the service part in Joe's possession has the correct 5692974 part number but has a flange with a rib that should have been produced in 1975 or later. There should not have been any orders from Chevrolet after April 1973.

Jim

[Joe L.]

Re: 66 L36 Harmonic Balancer, Steering coupler

I did find this bit of information today. The note on the Saginaw drawing "Inactive per 300,000 09JL80" means that the 5692974 Flange Assembly had not been ordered for service by the customer (in this case Chevrolet) for a minimum of five years. This note from the Saginaw Service Department informed the Saginaw manufacturing plant that it no longer needed to keep any special tooling in order to produce the part.

This 1980 Saginaw date is a seven years later than the April 1973 date that Joe Lucia found when Chevrolet discontinued the part for service without supercession. This fairly well fits the timeline of at least 5 years without any orders.

We still have the issue as to how the service part in Joe's possession has the correct 5692974 part number but has a flange with a rib that should have been produced in 1975 or later. There should not have been any orders from Chevrolet after April 1973.

Jim

Jim-----


I'm not 100% sure that this is actually a GM part. In fact, I'm starting to think that it's not. There is no part number on it and it came to me without its packaging.

On the other side of the coin, it has the "look and feel" of a GM part. The casting components look like GM pieces. The pinch bolts are definitely of the GM style and, even the headmakings are very typical of those seen on many GM fasteners and rarely, if ever, seen in hardware stores or industrial fastener suppliers. However, they're definitely of much later vintage; I've never seen this headmarking on 60's and 70's PRODUCTION fasteners.

Also, the piece looks to be of US manufacture, not foreign. There's just a different "look and feel" to the foreign stuff that almost always "gives it away". I believe I've had it for at least 10 years and more likely something like 15. I don't recall where I got it, though.

[Jim S.]

Re: 66 L36 Harmonic Balancer, Steering coupler

Joe,
I am sure that you have a Saginaw manufactured flange assembly. It may not be a 5692974. I may have more information in a day or two.
Jim

[Jim S.]

Re: 66 L36 Harmonic Balancer, Steering coupler

A little more pieces to the puzzle:

I talked with a Saginaw service engineer concerning the 5692974 flange assembly. As a favor he is going to do a little research on the part number.

However, he did provide some generic information. After a certain amount of time SPO runs a "DISCON" in house and if a part hasn't been requested for three years they drop the part. They provide no notification to the supplier that they won't be ordering it any longer.

So the way Saginaw protects itself from having tens of thousands of part numbers with no service orders is for Saginaw Service Engineering to run its own program at Saginaw. This allows them to purge their system of parts that SPO no longer seems to order. This is the reason for the "Inactive Per 300,000" note on the 5692974 drawing. However, SPO can come back and reinstate a part number if they begin receiving requests for the part from their dealers. This can cause Saginaw to scramble because suddenly there is an order for a part that their system had listed as "Inactive Per 300,000".

Lastly, with all passenger cars and most trucks no longer using flange assemblies (flexible couplings), SPO no longer orders any flexible couplings. The only Saginaw orders for flexible couplings are from independent suppliers.

I am beginning to think that (particularly for very old service parts) Saginaw supplies flange assemblies to the independents that are close to the original part but not necessarily exactly the same as original production.

Jim

[Joe L.]

Re: 66 L36 Harmonic Balancer, Steering coupler

A little more pieces to the puzzle:

I talked with a Saginaw service engineer concerning the 5692974 flange assembly. As a favor he is going to do a little research on the part number.

However, he did provide some generic information. After a certain amount of time SPO runs a "DISCON" in house and if a part hasn't been requested for three years they drop the part. They provide no notification to the supplier that they won't be ordering it any longer.

So the way Saginaw protects itself from having tens of thousands of part numbers with no service orders is for Saginaw Service Engineering to run its own program at Saginaw. This allows them to purge their system of parts that SPO no longer seems to order. This is the reason for the "Inactive Per 300,000" note on the 5692974 drawing. However, SPO can come back and reinstate a part number if they begin receiving requests for the part from their dealers. This can cause Saginaw to scramble because suddenly there is an order for a part that their system had listed as "Inactive Per 300,000".

Lastly, with all passenger cars and most trucks no longer using flange assemblies (flexible couplings), SPO no longer orders any flexible couplings. The only Saginaw orders for flexible couplings are from independent suppliers.

I am beginning to think that (particularly for very old service parts) Saginaw supplies flange assemblies to the independents that are close to the original part but not necessarily exactly the same as original production.

Jim

Jim-----


Your last sentence reflects exactly what I was thinking. By supplying parts to a non-GM customer, they would be freed of having to manufacture the part to an exact GM spec. In this case, for example, they would have used the later, longer pins since that's what they were using to build other couplings at the time and there was no negative consequence as far as functionality was concerned.

I'm sure that Saginaw would have had a minimum order quantity for making up a part like this, but some vendor probably met the minimum and ordered in enough to last for years as well as wholesale to other vendors.