Loose Pitman Arm

[Chuck B.]

The pitman arm is a loose fit on the steering box on my '56. It slides on and off easily without using a puller. The steering wheel has too much movement before the wheels start to turn. Is it most likely that the arm is worn (best case) or that the teeth on the shaft are worn which would require disassembly of the front end of the car to replace the sector shaft? Has anyone had to deal with this problem, and what did you do?
Thanks, Chuck

[Richard M.]

Re: Loose Pitman Arm

Chuck,

Was the arm loose on the splined sector shaft with the nut tightened/torqued, or was the nut loose? If the latter, then it may have been loose for a long time. Chances are that if is retorqued to spec it will be fine. However if there is damage to the Arm then replacement is necessary.

It is normal for the Arm to slide on and off before the nut is torqued. It's a tapered fit.

I had a similar scenario years ago on a '59. The car came to me for a body off, nose replacement, and complete restoration. This is what I found when I took the car apart. The big nut on the Pitman arm was so loose it only had a few threads left before it fell off. I was shocked that my friend who owned the car for 35 years never noticed how loose the steering was. He was lucky it didn't fall off completely when he was driving. This was only one of about a dozen safety items on his car that could have been disastrous.

This is how I found the Pitman Arm nut, ready to drop off.....


When I restored and rebuilt the steering box, I test fit the Arm. It was fine. I was able to torque to spec when back on the chassis. BTW this has to be done with the Pitman Arm supported by a wooden block against the frame so as to not stress the steering box internals of the worm and sector roller.

Rich

[Chuck B.]

Re: Loose Pitman Arm

Rich,

The nut is tight on the splined shaft, but there is enough rotational movement of the arm on the shaft that there is too much play in the steering wheel. When the arm is off, I can grip the shaft with a pair of channel locks and there is no play in the steering box. It appears that the arm has worn enough that it no longer has enough taper to snug down when the nut is torqued. I'm thinking that maybe like in your case, the nut was loose for a long time, and as the arm worked it's way off, the splines in the arm were damaged. I'm hoping that the wear is not on the shaft. New arms are not available, but used ones are listed on EBAY. I was hoping to have some confidence in a new old arm solving the problem before I buy an expensive one online.

I also have a power top that I purchased two years ago to install on this '56, so I'll be following along on your progress with your top. I'm also installing a new Al Knoch top which I've been warned is thicker than original top material and may cause a problem fitting down in the boot correctly.

Thanks for your response. Chuck

[Richard M.]

Re: Loose Pitman Arm

Chuck,

Sounds like it may be time for a Pitman Arm. That is a forged part and must have been compromised on its splines. That Sector Shaft is hardened steel IIRC, but double check it for damage when you get the arm off.

Keep in mind that the Corvette requires a unique Pitman Arm very different from passenger cars. Some on Ebay think they have a Corvette Arm when they really don't. Verify the casting number from yours to any out there for sale.

Rich
PS I have a bit of experience with the 56 power top. When you get there I may be of some assistance. There is a document and wiring diagrams I put together a few years ago which may help. I recommend you add relays to the solenoids for longevity. My doc talks about how.