C1 1959 Front Suspension-Upper/Inner Shaft

[Daniel S.]

Doing rebuild on 1959 front suspension. Bought front suspension rebuild kit from Corvettte Central. The caps with the grease fittings on are tight and does not have as much free spinning as I think it should. Found out threads are 11 threads per inch, 3/4 inch dia. looking for die to run on upper shaft.
Any suggestions?

Thanks,
Dan

[Joe R.]

Re: C1 1959 Front Suspension-Upper/Inner Shaft

Dan,

You may have the formula for disaster. I would employ the help of someone that has some experience with straight axle Corvette suspension. The kits are generally correctly matched and need no thread chasers. In the case of the front suspension, tight is usually good.

Regards,

JR

[Daniel S.]

Re: C1 1959 Front Suspension-Upper/Inner Shaft

Has anyone else ever run into this problem? More response would be
appreciated.

Thanks,
Dan

[John M.]

Re: C1 1959 Front Suspension-Upper/Inner Shaft

Dan,
I agree with Joe Ray. There is no off the shelf taps or dies that match the thread pitch and thread shape on C1 front suspensions that I am aware of. On the subject of upper/inner shafts, I would only reccomend replacement if yours are worn out. If you must replace the upper/inner shafts, it is wise to try and find some original GM ones, since the repro ones out there leave a lot to be desired and are way to big. Installing these oversized shafts can be a real pain. If kept lubricated, these shafts will last almost forever!

Regards, John McGraw

[William C.]

Re: C1 1959 Front Suspension-Upper/Inner Shaft

The shop manual indicates the relationship of the threaded section into the a-arm is a critical feature of this system in getting a low drag on the bushings and that an incorrect adjustment in this area will cause drang and subsequent wear. I'd check the drag on the bushings and shaft prior to installation and use that as a reference point. Significant drag "out of the box" would indicate a problem with the replacement set that cannot be corrected. Otherwise, the issue is with the installation of the shaft and the bushings, unless you have a bent upper arm.

[Tom P.]

Re: C1 1959 Front Suspension-Upper/Inner Shaft

For NEW upper-inner shaft bushings, they should screw easily onto the threads with essentially ZERO drag. Once screwed all the way onto the shaft (then back off about one turn, that's how they will be installed on the car), you should just BARELY be able to wiggle the bushing a tensy tinsy bit. They have to be loose enough on the threads for free movement AND for grease to fill into the threads. Be ABSOLUTELY sure the threads of the bushings are clean. It is possible there is some debris in the new threads! If after all that, they are still dragging when you screw the bushing onto the shaft, I'd give the vendor a call and see about an exchange for a replacement.
Now then, once a new upper-inner shaft, bushings and upper A-frame is installed onto the cross member, the A-frame should be stiff enough that when raised by hand, it WILL NOT fall by its own weight, even after it's been greased. It will loosen up just fine after a few miles (although you are not going to tear it down just to see if it will fall of its own weight).
As mentioned, the key to long life for these old frontends is to keep them greased.

Regarding the tight fit of replacement shafts into the cross member, they are supposed to be tight! Replacement shafts are supposed to be about .008 oversize. You DO NOT want the new shafts to be a loose fit in the cross member! YEP, I agree, new shafts are a bear to install, but that's really a good thing.