Have a 1971 convertible. Does anyone know the diameter, thread pitch, length and grade of the capscrews required to attach the steering column to the steering box? (connecting the rag joint between box and column)

Thanks for your help!

 

The pinch bolt was GM #7807271 and is no longer available through GM dealers. However, the bolt is still available through most Corvette suppliers.

It is a special 3/8-24 UNF bolt with a long (0.570 inch) shank that extends more than half way across the notch in the mating steering column and the steering gear shaft(s). This insures that the bolt can't be just loose and the spline on the column or gear shaft just mesh with the bolt threads and the steering components come apart.

The bolt also has a 12 point 7/16 head. I don't know why the special 12 point head. The bolt was designed that way in the mid-1960's and the guys that designed it are long gone.

Jim

 

Thanks. Is this the same bolt that connects the joints on the coupling? I ask b/c I have this bolt in one position already. This is also known as a 12 point or a counterbor screw. An actual brand is "Count-r-bor" and the company I work for sells these, but without the patch. I can't explain this correctly I don't guess, but I have this bolt used to attach around the spline. I'm looking at the two bolts used to connect the two halves of the coupling together if that makes any sense at all. Is this bolt used there as well? They are missing so I have no clue.

 

The bolts that connect the two halves together appear to be common 3/8 x 1 bolts.

 

While we're on the subject, two questions:

First, if you look at the pic above, there is a fair bit of the splined shaft showing at the top of the rag joint. Is there a spec somewhere for how much is acceptable? Mine looks pretty much the same and I've always wondered if the steering shaft had been compressed at some point.

Second, I don't think that the aftermarket bolts (or the old ones for that matter) still have the nylon insert. Will a drop or two of Loktite serve the same purpose?

 

You can buy these bolts at Automotive Fasteners, but there may be a $10 minimum purchase, but they have other things you may be looking for. These would be 3/8-24 x 1-1/4" long based on Jim Shea's information above. The length of a bolt is measure under the head unless it is a "flat head" or what you would call countersunk head. The closest to the 1.19" mentioned above is going to be 1.250" long. It is a Counterbore or brand Count-r-bor or also a 12 point. You can use Loctite and in this application, based on the diameter of the fastener, you would use Loctite 242 which is a blue, medium threadlocker. Can also get at Automotive Fasteners or parts stores. You don't want 271 or red in this application. it is considered permanent and requires either special tools or heat to loosen it. The nylon patch is not a permanent locker so use the 242 blue.

 

Are you also talking about the two shoulder bolts that attach the steering column flange to the flexible coupling itself?

They are very special shoulder bolts. They impart a controlled squeeze on the rubber disc and also provide a metal to metal attachment to the steering column flange.

Jim

 

I guess I am, but mine were not shouldered. Where can I get these? Also, I don't have rubber on my unit anyway. rag on one half and metal on the half coming from the steering column side.

 

BTW, the drawing that I included (above) on the GM 7807271 is not the complete drawing. I would not even attempt to purchase some type of bolt that is only "similar". The length of full 3/8-24 thread is very, very critical. A "similar" bolt could run out of full thread as you tightened it into the gear (or the steering column) flange. That could result in a loose connection.

The nylon patch (or lack of a patch) is probably the least critical of the features on the bolt drawing. The patch prevented the bolt from being installed just "finger tight". The patch required that you had to use a wrench to seat the bolt and to tightenen it to specification. You could not just insert the bolt with your fingers (so that it looked tight) and forget to torque it to specification (30 ft-lbs). Again, you are steering your car through this connection!!! The use of Loctite can't hurt but it really isn't required for a safe connection.

That same bolt was successfully used from 1963 through 1967 without a nylon patch.

You should be able to find the exact bolt at numerous Corvette suppliers. The bolts were used on millions of GM cars and trucks through the 1990s. The bolt is no longer available through GM dealers although you might still find a dealership with one left in the parts bin.

Jim