Control arm bushing

[Wwabbit]

Scott-
I'm pretty sure it's a FGT. Don't ask me how I know that. The pic is taken standing under the center of the car looking outward at back of the knuckle. The vertical member in each pic is one of the knuckle's arms. Here's the right rear. In both pics the nut points to the rear of the car. Both pics are oriented correctly. As you can see this side is a bit uglier (still don't know if that's bad or not though). if you poke at it with a screw driver, black ooze comes out. I thew the screw driver down and ran.

 

[Wwabbit]

Found one more pic.

 

[RALPHIE]

I think that some of you are looking at front A-arms and WWabbit is concerned about the rear attachnents!! Don't print front A-arm items when a need for a rear solution is required.

 

[sahlman]

Found one more pic.

View attachment 28756

Ok, I see it Wabbit. My poor mistake. I knew you know an FGT...just thought it might be a different pic than intended. but i got t now. I will work to reply tomorrow on your post and the other follow ons.

 

[sahlman]

Scott-
I'm pretty sure it's a FGT. Don't ask me how I know that. The pic is taken standing under the center of the car looking outward at back of the knuckle. The vertical member in each pic is one of the knuckle's arms. Here's the right rear. In both pics the nut points to the rear of the car. Both pics are oriented correctly. As you can see this side is a bit uglier (still don't know if that's bad or not though). if you poke at it with a screw driver, black ooze comes out. I thew the screw driver down and ran.

View attachment 28752

WWabbit, at this point the whole arm requires replacement if you are oozing grease out of the joint. I will clarify a few points made prior on why we went with integral joints, but one failure mode I did not discuss is damage to the boot/seal on the joint. These are heavy duty boots/seals. It appears that the boots/seals on the rear lower cross axis joint (this type of joint) has some damage (holes/tears). Is this a correct statement? Grease should not be oozing out otherwise. We did not see grease oozing/joint issues in thousands and thousands miles of testing including our high mileage durability cars (over 50,000)

Replacement of these joints (outer balljoints or inner bushings) has some risk if you could get the joints as they are not intended to be replaced. These are custom joints that the manufacuter cannot sell to any of us inidividually at this point. Even if you could get the joints they require a pretty high minimum push out load to make sure the joint stays in place and does not start walking in the bore.

The chance of damage and issues on push out of the old and push in of the new is real and needs significant testing to see if it is doable. I having parts CNC'd now for testing of my first FGT chassis procucts for sale this spring, which I will give details on in about 3-4 weeks. This is not control arm work, but I have thought about that topic a lot, so that may be the next system I go after. However, that is a very significant endeavor and I will have to look at it closely.

Scott

 

[sahlman]

A couple of questions:

Was there ever an average life expectancy established for these pieces?

What’s the current going price for the replacements?

The life of these joints should be well over 50,000 miles...as long as the boots/seals don't get damaged.

I believe the current cost of a sull set of forged arms is about $12000 list at the dealer.

 

[sahlman]

I found it interesting that the document list this as a caveat:

The integral joints chosen are designed to last the life of the car (as long as it is not
crashed or hit significant potholes)

I've seen what I feel are pretty significant potholes on major interstates that sometimes cannot be missed.

Did any of the Ford GT's used in the race world use any type of mono-ball bushings in the a-arms?

Cheer,
George

Potholes - insufficient detail on my part trying to keep the explanation to 1 page. I am referrring to something approaching our worst case for testing, which allows the tire/wheel to nearly drop 6" into a square pot hole with the driver on the brakes at the same time at 55 mph in which you are trying to rip the suspension off the car. This type of pothole event will destroy a lot more than the balljoints or bushings including forged rims, bent control arms, etc.

Detroit area is brutal with crappy roads and potholes...no issue in all of our testing. So I am referring to an extreme.

Any of the significant race cars (Matech, Doran, Robertsons, etc) all had their own custom chrome moly control arms, different geomertry and yes all spherical joints - no bushings.

Scott

 

[PL510*Jeff]

The life of these joints should be well over 50,000 miles...as long as the boots/seals don't get damaged.

I believe the current cost of a sull set of forged arms is about $12000 list at the dealer.

If mine can be used as an example double the 50k figure.

 

[sahlman]

Jeff, Thank you for the comment. For sure these joints typically last 150,000 miles plus...but the GT is obviously not typical and we did not have enough test data with the GT to confidently and conservatively say they could make it that far. 50,000 miles is very conservative and we did have test data to 100,000 miles that said they should not have issue.

Scott

 

[MTV8]

If the boot is just cut and not damaged otherwise, would it be possible to seal it in some way to keep from replacing the entire arm?

 

[Wwabbit]

If the boot is just cut and not damaged otherwise, would it be possible to seal it in some way to keep from replacing the entire arm?

Great question.

 

[Indy GT]

I understand the intent of not having to replace a costly A-arm due to "just" a compromised grease boot. But HOW would you propose to repair a rubber boot which now has grease all over the area of failure with a "patch" that has elastomeric and internal pressure qualities equal to the OE boot?

There are many smart and creative owners out here. Just wondering how someone would propose a boot salvage fix....

 

[Wwabbit]

I understand the intent of not having to replace a costly A-arm due to "just" a compromised grease boot. But HOW would you propose to repair a rubber boot which now has grease all over the area of failure with a "patch" that has elastomeric and internal pressure qualities equal to the OE boot?

There are many smart and creative owners out here. Just wondering how someone would propose a boot salvage fix....

Granted it would be a toughie, but we do live in an age of new and interesting materials. J P Morgan told Edison his telephone idea would never amount to much.

 

[Specracer]

Well now.....

J Paul Getty told Edison his telephone idea would never amount to much.

 

[jcthorne]

I have used a self vulcanizing rubber repair tape to repair ball joint boots on trucks. The stuff is mildly adhesive in its shelf state off the roll but you stretch it as its applied and the layers bond to become one rubber piece with the elasticity of the original tape. Its pretty interesting and tough stuff. I usually only use the black but its even available in colors. I will try to get the brand name tonight.

This application might be more difficult because of the narrow application site. But as the boot is only to keep dirt out, it might be worth a try. As long as the joint is kept clean and well greased....

 

[sahlman]

John sent me a bunch more very good pictures of the joints. The boot is really hurt on the back side of the joint (toward the rear) on both left and right rear while the seal at that joint toward the front is in pretty good shape with minor signs of issue. I am not sure what has caused this, but it sounds and looks like the boot is deteriorating badly as though it is really old (which it is not) or heat damaged or just a bad batch. Very strange to be happening on one side of the joint. We did not see any issues of this nature with this joint.

I am skeptical of the ability to reseal this badly hurt and small area boot in addition to concern about how much grit and contaminents are in the joint now. It is possible, but not probable (reliably) and I am not sure the damage hasn't already been done to some degree and will get worse on a safety critical part. It seems unlikley that it will fail suddenly, but it also doesn't seem worth risk.

Let us know if anyone else notices boot damage like John's.

 

[Xcentric]

Is it possible the bushings were contaminated externally by something (a solvent) that attacks polymers? I'm assuming the "rubber" is synthetic.

 

[andreikoc]

I like JCThorne idea as the actual motion is only a few degrees. Probably works for a long time. It would be physical containment of the goo. Just be diligent and get a few wraps in.

 

[Wwabbit]

Is it possible the bushings were contaminated externally by something (a solvent) that attacks polymers? I'm assuming the "rubber" is synthetic.

Have never used brake cleaner back there. Wiped rotors with acetone once between pad changes; wiped not hosed. And have never directly cleaned the area or part in question.

 

[ultrasportracing]

As far as I can tell the rubber boot is the only damage, if the joint has no wear then replacing the sealing boot is no problem, just look for one that is similar, It is not part of the joint as far as I can tell, just a c clip holds it to the joint, crack the joint and have a look.