Rear control arm question

Regan Burba

Regan Burba

True Classic
Due to rust I need to replace the left rear control arm on 87 X. I have an extra right side. I’m figuring the answer is no, but I have to ask, can the right side be used by flipping the ball joint?
 
Can you post a pic of your rusty control arm? I'd like to look and see one that's bad enough to scrap from rust. That's a lot of metal to get eaten away.
 
I’ll try to get a picture this weekend, it’s at a friends house right now for the winter.
The extra right sided one has rivets holding in the ball joint, would that mean it would be older and not fit an 87?
 
Regan Burba said:
I’ll try to get a picture this weekend, it’s at a friends house right now for the winter.
The extra right sided one has rivets holding in the ball joint, would that mean it would be older and not fit an 87?
Click to expand...

The left arm also has a stamped depressed area on the upper surface of the forward leg, which is needed for clearance due to the 5-speed trans being a little longer than the 4-speed. If somehow a flipped right side one would line up, you would still have to make the clearance as well as any ball joint-related changes.
 
Thanks, did not know that, I’m glad I asked before messing around with it. I’ll get picture soon, I’d like to get your thoughts on it.
 
I've seen where the ball joint has been removed for replacement/rebuilding, then reinstalled. So that portion of it should be doable. I think you could be able to hold the two arms side by side to see if they are the same when one is flipped over? Adding the clearance for the trans looks like nothing more than a dent on the open edge of one sidewall on mine. At first I though it was the result of hitting something in the road or a poorly placed jack, etc before realizing it was intentional. Kind of a sloppy way for the factory to do it in my opinion. But easy to replicate.
 
Dan Sarandrea (Phila) said:
The left arm also has a stamped depressed area on the upper surface of the forward leg, which is needed for clearance due to the 5-speed trans being a little longer than the 4-speed.
Click to expand...

I wonder if that's the same reason that this K20 swap had a cutout in the suspension arm as noted by Dennis. Most of the K20 swaps I've seen use later model exxe's because the MWB kit requires later hubs in the rear. I never checked my drivers side rear swingarm when I was fitting the K20 drivetrain. I'll ask Matt or Brayden at MWB on Monday.

Since mine are out and easily accessible, I took some photos (it's from a '76). The box sections are identical, but you'd need to swap the ball joint to the other side by grinding off the huge rivet and replacing with a super strong bolt system.

IMG_1435.jpg IMG_1434.jpg IMG_1433.jpg

from the side they're the same:
IMG_1436.jpg

the underside/inside:
IMG_1437.jpg

There is a thread somewhere here describing replacing just the hub on an existing arm (vendors sell the entire arm assembly).
 
Thanks for the photos, they do appear to look the same. When I bring the car back home (when weather warms up) I’ll have to take the left side out and compare.
 
Simply bolting the ball joint on to the A-arm risk shifting of the ball joint under load. This is why some of these A arms have welded ball joints. This is why Rivets were used as Rivets tend to fill the hole once driven and seated in place preventing joint movement under load.

If these ball joints must be bolted to the A arm, the mounting holes must be drilled-reamed with a precision fit (0.001" +/-) to the unthreaded area of the bolt or precision drill locating pins then allowing the bolts to apply tension to the joint with the pins doing the joint locating.

Anything less risk shifting of ball joint location under load.


Bernice
 
EC566376-D227-4050-8E27-2F6A93B38D76.jpeg
Here is a photo of the rusted control arm I was referring to. The rest of it is not bad, but I was concerned about the placement of the rust near the bushing. Any thoughts on whether it’s worth trying to save?
 
That is unusual looking for that much erosion in only one place.

The rest of it appears to be fairly solid from what I can tell in this photo (but really cannot tell from just a photo). Usually things are worse than they appear on the surface.
IF the rest of the arm is not eaten by rust, and IF this is an isolated spot with such corrosion, then you MIGHT be able to take the arm out and do some repairs...by grinding out all of that rusted spot and welding additional bracing to replace it. But you will have to closely assess the condition of the rest of the arm first. A good sand blasting of the entire arm or similar clean up is needed to see how far the rust goes.

I suppose it's kind of a trade-off between trying to repair that arm vs converting the other good arm you have to use on this side. Getting a good used arm as a complete replacement would be even better, but that might come down to budget.
 
Regan Burba said:
View attachment 7752 Here is a photo of the rusted control arm I was referring to. The rest of it is not bad, but I was concerned about the placement of the rust near the bushing. Any thoughts on whether it’s worth trying to save?
Click to expand...

I think it depends upon whether you have the time, tools/equipment, and skills to remove the rusted arm and do the metalwork as Dr. Jeff described.

If so, then sure, remove it, blast it, repair it, and replace.

If not, then replacing it with the wrong sided one after flipping the ball joint might sound like the next-best plan, but if you had the time, tools/equipment, and skills to the flip, then you would by definition have the time, tools/equipment and skills to do the repair, which is preferred to the flip.

So if insufficient time, equipment/tools, and or welding/fabricating skills are the case, neither the fix not the flip is a viable option. In that case, IMO buying a good used unit for the correct side is your best option.
 
I would replace with a proper side arm. We are talking about a major suspension arm. I'm one of the cheapest guys on this forum but there are even limits to my cheapness.
 
Thanks for responses, I have the means to be able to repair it but that may be a difficult place to weld in a piece. I’ll have to get it off and take a better look at how the metal is around the rust hole. If I can find a replacement at a good price I would rather go that route. If it looks like the right sided one will work I’ll try that. Carl if your one of the cheapest members on the forum I’m probably a close 2nd. This is a fun hobby but I can’t go crazy with things because as many of you know kids can be expensive too.
 
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