I have searched and searched, but it seems there is no thread discussing this topic.

Like many people have experienced with the C6 upper control arms, mine are starting to slide out of the bushing. This car was run hard by a previous owner doing autocross. I'd like to replace them while I install DRM shocks, and have considered a few different routes:

1. Replace with OEM C6 UCA's ($284)
2. Install Global West KT-C56F Del-a-lum kit ($790)
3. See if C7 UCA's will work ($190)

From what people have said, the C7 has a much better bushing design. Has anyone installed them on a C6, and if so, do they have the same geometry? The C6 OEM UCA's are two part numbers, 10356433 (Left) and 10356431 (Right). The C7 uses a single part on both sides, 23158030. The C7's are $94, versus $142 for the C6's. Also, looking at RockAuto, Mevotech has two part numbers that say they are compatible across C5 through C7. However, Moog only has control arms specifically for the C6.

My main reason for researching this is:

• My car is only street driven, so the Global West kit at $790 is probably overkill, although it will hopefully tighten up the pretty loose and unsettling suspension (fixes LCA bushing deflection as well).
• I want to save money, and the C7 UCA's (at ~$190) should not have the same problem that the C6's have.

Any thoughts or insights on this? Thanks!

 

I suspect that two different C6 part numbers indicates the stock UCAs have some sort of an offset whereas the C7 UCAs don't have an offset. Even if the C7 UCA might fit the two mounting locations the location of the upper ball joint will be fore or aft of the stock location. You might be better off seeing if you can source a good used C7 UCA out of a wrecking yard and use that to make comparisons to the stock UCAs.

Bill

 

Good suggestion on a salvage yard. Unfortunately the ones around me had ridiculous prices. I ended up ordering a C7 one from Rock Auto. I plan on setting up a simple jig to compare dimensions to both left and right ones off my C6.

 

Interesting, let us know what you come up with.

 

Changing control arms isn’t gonna solve the problem of the bushing getting pulled through. You need to change the bushing themselves.

You can just buy the bushings you need a la carte from this supporting vendor, https://www.borgmotorsports.com/coll...idual-bushings

 

Thanks for sharing the link! That is exactly what the individual bushings are meant for. Well, that and Pro Touring builds.

 

I haven't seen reports of issues with the C7 control arm bushings getting pushed out though.

 

The C7 control arm will be here later today, but I pulled the uppers off my car this morning. I haven't done any measurements yet, but by the eye each side seems to be same. However, the angle of the ball joint taper will have an impact, so I'll have to measure that too.

I actually just noticed that the previous owner had done the modification to reverse the rear bushing in each one.

 

Your control arms appear to have been re-assembled incorrectly.

Mine came from the factory with the metal flange on the outside of either bushing. This captures the arm between the bushings.

Every other upper arm I've seen is the same way.

Yours have the flange on the same side of both bushings, so the arm can shift backwards.

 

That's what some people (and obviously the previous owner of the car) have done to correct the issue of the control arm slipping out and bending due to repeated hard braking. I don't believe there is much force that operates the opposite direction, which is why it can work. See this thread - https://www.corvetteforum.com/forums...pping-out.html

 

So I think I went overkill here. I could have just done measurements of the control arms themselves, but I made an imprecise jig out of wood to mount up the control arms. I machined a tapered piece out of aluminum that fit snugly in the tapered bore, and threaded it to screw in a rod with a pointed tip to measure the center of the bore at different heights of the control arm. All very imprecise, but with one caveat, I'm fairly certain C7 upper control arms have the exact same dimensions as both left and right C6 arms, just with a different bushing design.

I measured both the left and right control arms, and it resulted in them being slightly different caster wise, they were pretty much exact camber wise. I could chalk this up to the bushings not being centered possibly? When I measured the C7 control arm, it was dead center between the two. Any slight difference in caster can easily be resolved through an alignment.

The only concern here is the resting height of the arms. Both left and right C6 arms had a much lower resting height than the C7's. And actually, I'll have to mock it up in the car, but it seems the C6's would cause strain on the bushings at ride height, where as the C7's would be less stretched (or twisted?) at ride height. And if the control arms are in fact functionally the same, why would GM just replace the C6's with the C7's in the catalog? And other than the elongated holes on the dog bone mounts being on opposite sides, why would GM have two different parts for each side?

Anyways, here are the pics:

 

I may be completely out in left field here, but looking at what you've shown and considering what you're trying to do, I think I would simply make new wishbones with some modifications that allow an additional threaded stop on the opposite side. Maybe add a Delrin bushing and Bob's your uncle. Seems easier than dealing with the control arms.

 

I'm not quite sure what you mean.

 

The weight of the car will take that preload out. They are all different . For the money I would have thrown poly uppers in and moved on......or go all our with the Delrin!

 

You're probably right, poly is probably the most cost effective way to go. And as for the preload, my only concern was if at ride height the bushing is constantly preloaded (twisted), if it would wear out sooner.

I'm going to order another C7 upper control arm, install them, and consider it done. If this wasn't just a street car, I'd go a different route.

 

This was an interesting read. I have a set of control arms with poly and a T1 set. I ended up using the T1's because they gave me the best overall performance that I was comfortable with.

I bought my car new in 2006 and the T1 arms have been on for almost 10 years with no bushing issues.

 

I bet you're right. If it's an effective design with known durability, it would make sense for GM to keep moving forward with the design.

That is likely a fair assumption (on the caster). On the resting angular position of the trunnions, it's likely that the C6 bushings have just been twisted in the arm. I've removed several trunnions/bushings by hand. It's just a factor of the design and likely why GM changed for the C7. Potentially the engineers chose a different design philosophy on the contribution to the wheel rate from the bushing.

 

They work on a C5. Discussing with Lane @Borg Motorsports and Louis @GSpeed they both helped confirm fitment and saying C7's don't have this inherent bushing push out issue. For my needs this was a perfect fit.


C5 arm on top C7 on bottom. You can see how there is less bushing on the outside plus a large flange face to keep arm from moving as far.


Installed. Bolted right in with no issues.

$98ea from RockAuto and arrived in a week. Beats the CRAZY prices people want for C5 arms

 

 

JonnyCap: What's the difference between the marks on the plywood, 1/8"?

JonnyCap and smitty2919: Have either of you had an alignment since installing? Any problems?