I am in the process of replacing the lower ball joints on my 84 Corvette. I got new joints from NAPA and I measured them before I installed them.
I found the new joints to be .015 larger than the ones that I removed.
I also measured a set of TRW and Moog ball joints and found them to be the same as the NAPAs. I am hesitant to try to press these into the control arms, because I don't want to damage the bores. What am I missing. The control arms did have Z51 stamped on them, but the parts stores all claim the 84 up use only one type of joint. Any help would be appreciated.
Dave

 

This is a common issue. It is Not a question of the year or suspension option code - this is how replacement ball joints are going to measure.

The simplest solution to making the replacement joints "fit" is to take the joints to a machine shop and have them turned down by .015". then use the "freeze the joint and bake the socket" approach to shrink the ball joint and expand the bore in the lower arm before pressing the joint in.

It is NOT necessary to reduce the diameter of the new joints if you are prepared to be aggressive with the heating/freezing technique. Just Never use an open flame (like a gas torch) on the aluminum control arm to warm it up - the flame temperature is much too high and can heat the surface of the arm enough to effect the heat treatment, and even Melt the thing.

Use an oven, or a gas grill (with a guard between the propane flame and the alloy part, just in case, although the propane flame is not really hot enough to hurt anything) to heat up the control arm. 250-300 degrees F should be plenty - you can measure the bore as you heat the arm and see the size change. Likewise measure the frozen ball joint - when the two have grown/shrunk such that there is a zero fit, or even clearance, then stick 'em together...

There are also inductive heating applicances out there that can be used to heat the bore in the arm, although I personally have never used one (yet - something that is on my toolbox wish list..).

Oh - far better to locate and use an actual Press to do this job, and Not use a hammer and vise. Or even one of the C-clamp type tools - not as good as a real hydraulic press, but going the right direction..

 

Thanks for the response, but I am still at a loss to understand why the difference in dimensions of the OEM vs the replacements.

Dave

 

Replacements are a little larger to make up for sometimes the hole gets out of shape when the old ones are pressed out.

I just took mine to the machine shop and let them do it.

 

I noticed this when I replaced mine this last summer.PITA to press them in with a ball joint press tool.Maybe A/C Delco's are correct size?My advice is bring to machine shop,use a press,use the heating & cooling method or force them in with the tool until the C clamp starts bending.Make sure the ball joints are going in straight if using last approach.Don't use a hammer to remove or install

 

I have a hydraulic press and I planned on heating the aluminum control arm and freezing the ball joints before assembly, but .015 difference in parts bothers the heck out of me.
Dave

 

a one thousandth of an inch (0.001") or so is considered an interference fit. but fifteen thousandths of an inch (0.015") seems (more than a little) excessive.

 

a one thousandth of an inch (0.001") or so is considered an interference fit. but fifteen thousandths of an inch (0.015") seems (more than a little) excessive.

I agree and cant believe that more C4 owners haven't had to address this issue.
Dave

 

I didn't mic mine to see how the new Moogs compared to the OEM joints, but they pressed right in (hydraulic press) with a little heat on the control arm and some grease on the ball joint. Maybe things are different on a '94.