Rag Joints

[Jim S.]

Re: Rag Joints

I was a product engineering supervisor at Saginaw Steering Gear Division, GMC, from 1971 through 1986. I was responsible for flexible steering shaft coupling assemblies. So a lot of basic design work was done on connection designs just before I became supervisor. The following are the basics.

The first thing to remember is that we are dealing with a critical safety connection with respect to steering your car. That criteria was always foremost when making any type changes to the flange to steering gear, or flange to steering column shaft connections.

This is the philosophy concerning the flex coupling flange connections. Tightening the pinch bolt to a specified torque was designed to "wrap" the flange barrel around the gear input shaft. That is why, in most cases when working on a vehicle, the pinch bolt is removed and yet the flange still needs to be "persuaded" to come off the shaft. You usually have to jam a chisel point or a very large screwdriver into the saw slot in the flange barrel and cause the barrel to open slightly before the flange can be slipped from the shaft.

Early flanges (1963) had full serrations and it was noted that serrations all around the interior of the flange barrel actually hindered the "wrap". So through the years, based on tests, the number and location of the serrations were modified. On the 1963 to 1966 drawing above you can see where serrations were eliminated on 1/4 of the interior of the barrel. For the most part, serrations were eliminated to improve the "wrap". Please note that the Saginaw flange drawings in many cases were updated to reflect the latest design for service parts. That is why my 1963 drawing doesn't necessarily show the full serrations.

Also, starting in late 1969, a flat was added to the gear input shaft and a corresponding flat was added to the coupling flange. The flats aided in installing the coupling assembly in the correct rotational location. This eliminated several more serrations where the flat was located.

For the most part, if the pinch bolt was torqued to specification, the connection was secure for the life of the vehicle. Problems could occur if the pinch bolt was not tightened. So a nylon patch was added to the pinch bolt threads in 1969 such that you cannot install the pinch bolt with just your fingers. You must use a tool to draw it down. Therefore, it is assumed that if you used a tool, you would also apply some amount of seating torque.

In my humble opinion, if the pinch bolt is torqued to specification (i.e. 25 to 35 ft-lbs) the connection would be secure regardless as to the number of serrations.

Jim

[Larry M.]

Re: Rag Joints

Jim....that is good information and somewhat what I was thinking might be right. but you didn't answer my specific question. In the pictures about 45% of the ribs/splines remain. Is that enough for any design say up to or through 1966 or even later....prior to adding the flat? Is 16 ribs enough? My gut tells me that it is in practice but even then is it consistent with any GM revision?

[Jim S.]

Re: Rag Joints

If the pinch bolt was loose (for some reason) and the vehicle driven for a long time , I would think that all of the serrations would be wiped out, not just some of them. I don't think that the actual number of serrations machined in the coupling flange would make a difference. With the pinch bolt properly torqued, even if there were no machined serrations in the coupling flange, I would think that the splines on the gear input shaft would dig into the coupling flange and the "wrap" would insure that there would be no slippage in the connection. This is my best estimate as a retired engineer.

Jim

[Joe L.]

Re: Rag Joints

If the pinch bolt was loose (for some reason) and the vehicle driven for a long time , I would think that all of the serrations would be wiped out, not just some of them. I don't think that the actual number of serrations machined in the coupling flange would make a difference. With the pinch bolt properly torqued, even if there were no machined serrations in the coupling flange, I would think that the splines on the gear input shaft would dig into the coupling flange and the "wrap" would insure that there would be no slippage in the connection. This is my best estimate as a retired engineer.

Jim

Jim------


For what it's worth, I agree with you.

[Gary R.]

Re: Rag Joints

I would lock it on the input and see how it is, as mentioned by Jim and Joe. The iron is going to "crimp" around it as well. I sometimes have to spread them open when fitting to a new input.

I still haven't seen anything for L69-82's that is a quality part. Long Island has very good 63-67's, the 67's also fit 68 & E69.

[Jim S.]

Re: Rag Joints

I wish some aftermarket specialist company such as Cardone would decide to manufacture a whole line of flexible couplings. There was a company by the name of Garlock (out of Palmyra, NY) that manufactured the laminated rubber coupling disc for Saginaw. I heard (after I retired) that Garlock could no longer purchase the fine metal grounding screen and ceased being a source for the coupling disc. Their construction of neoprene rubber and cotton cloth laminations were very high quality. All coupling discs were the same dimensionally. However, all Corvette discs (whether power or manual steering) had 7 laminations of rubber and cotton cloth. All other GM pass cars and trucks with power steering had 4 laminations. All other manual steering systems used a 7 lamination disc.
Jim

[Larry M.]

Re: Rag Joints

I want to ask my question differently. I think it is established that the splines as pictured will most likely work. But under the NCRS mantra are they original configuration having only 16 splines/ribs? The drawing shows 24 but your experience may say they look like others (hopefully many others) you have seen. I don't own this and am wondering whether to buy it. Otherwise it is configured as the one on my car and maybe in better condition. Now I know that some NCRS guys say that if you can't see it on the car then it doesn't matter. Other more anal types like me would rather the part be totally correct if possible.

[Jim S.]

Re: Rag Joints

Larry,
Saginaw was a virtual 100% supplier to General Motors for steering gears and flex coupling assemblies in the 60s through the 80s. Sagiinaw became 100% supplier of steering columns 1967 thru the 80s. So there was a big advantage being the sole supplier of the entire GM steering systems.

Saginaw was very good at trying to keep proliferation of coupling assemblies to a manageable level. Original coupling assemblies (1963 to 1966) were installed in Corvette and other vehicle chassis where solid shafts were the norm. So short length stop pins (rivets) were acceptable to engage the steering column flange. With the advent of collapsible steering shafts (in 1967) it was noted that in some dynamic conditions the steering shaft could be collapsed and the flexible coupling assembly could be distorted (i.e. pulled apart) by some amount. So it was decided to lengthen the stop pins so they would remain in engagement with the steering column flange even under minor pull apart conditions. Since longer rivets were good for collapsible steering columns it was further decided that longer rivets could also be used on earlier assemblies.

This same type of reasoning was also used when screen ground coupling discs came into production. Screen ground discs were more reliable and less expensive than ground straps and ground wires. Again after 1971 nearly all service coupling assemblies were manufactured with the screen ground disc.

If I might interject my humble opinion, whether a flange had 6, 12, 16, 24, or 36 splines it is impossible to determine until you disassemble the flex coupling assembly from the steering gear. (This service procedure requires either dropping the steering gear from the frame or dropping the steering column.) Now, compared to disassembling the vehicle to count splines, you can run your finger along the edge of a flex coupling disc and if you feel fine wires poking into your finger, that vehicle should be 1971 or later.

Jim