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S197 Upper Control Arm (UCA) Bushings

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Recently there was a very informative discussion on the benefits (and limitations) of the different types of UCA's available in the "3Vs...We're Not Dead Yet!" thread (link below). Aftermarket vs OE, fixed length vs adjustable, poly vs spherical bearings, etc.

https://trackmustangsonline.com/threads/3vs-were-not-dead-yet.14924/page-4

There's a strong consensus that the OE UCA was/is adequate for several road race teams, so why fix what isn't broken. I'm leaning heavily this way as a replacement to my current Whiteline UCA, which is their 2nd gen poly on the chassis side, not the new style with Max-C. I suspect my differential bushing needs to be replaced, and I want to move away from the poly bushed Whiteline unit.

In my research, most discussions are around the UCA assembly itself, and very little discussion around the bushing on the differential end. Did the race teams that ran the OE UCA assembly also run the OE differential bushing? What about the 302S cars?

Also, I discovered that Ford used a different differential bushing on the 2014 GT500s. This was only on the 2014's and not the 2013's or earlier. Pictures look identical, just different part number and double the price. My guess would be a design change to handle the higher power outputs of the last run of GT500s, which could perhaps be a more robust OE version for track use? Hoping that someone on here perhaps has tried the GT500 bushing and could provide feedback.

Standard GT and earlier GT500 bushing part #: BR3Z-5A638-B
2014 GT500 only part #: DR3Z-5A638-A

Appreciate any insight here.
 

Norm Peterson

Corner Barstool Sitter
939
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a few miles east of Philly
Here's all I could find in FRPP catalogs for UCA bushings. Would still like to know more, since at one time I think a "28% stiffer than base" note was included with the early GT500 LCA description.

MUSTANG FR500C REAR UPPER CONTROL ARM BUSHINGS
M-5638-R
• Service replacement for the Mustang FR500C race car
• Includes bushings and sleeve for upper rear control arm
• Increased durometer bushing for precise handling and control


Norm
 
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@67GTA, the teams ran them because they had to according to rules. If they had a choice they would not have.
If this is for your race car, look at the Steeda adjustable with heim and large spherical on the axle.
May not be for everyone, but for me it works very well. I like firm, solid, no slop, no bind, but I do like adjustability.
Probably one of the best mods I have done to the car.
 

Norm Peterson

Corner Barstool Sitter
939
709
Exp. Type
HPDE
Exp. Level
5-10 Years
a few miles east of Philly
A few thoughts on the UCA

A UCA has only one actual job to do, keeping the axle from rotating as seen in side view. Everything else is a consequence of the details of its design – side effects, if you will - which can be selected or adjusted to suit different requirements. The good news is that there is some choice in how you tweak these details. The bad news is you have some choices to make.

As far as the pivot details are concerned, there are two schools of thought. Either lock the movement at the top of the differential housing down to only what the linkage geometry (UCA & LCAs together) permits, or introduce a little compliance to soften the ‘hit’ from suddenly applied loads. Both have advantages.

I’m guessing that the majority of Mustang owners looking to improve their cars’ rear suspensions come into suspension modification with a drag-racing orientation, where stiffening up (by any means) all those relatively soft OE control arm pivots is just part of what you have to do. The un-glamorous part, compared to engine and powertrain mods. But simple works for them, even if by the cheap way out (poly/poly) some extra “bind” gets added in the process. Turns out, that “bind” can actually work to their advantage in straight line acceleration, “bind” mainly amounting to additional rear roll stiffness, which helps “re-plant” the right rear tire against driveshaft torque reaction trying to unload it. Making left vs right traction closer to equal = improved acceleration, and even if it’s only a tiny bit better, it’s still a good thing as far as drag racing is concerned.

But when you’re a corner-carver, priorities change. You don’t want “bind” (you can’t tune how much of it you're getting), and you may or may not want movement at the top of the diff housing locked down to geometrically permitted movements alone. On the one hand, you don’t want so much bushing compliance that you risk getting into wheel hop, but on the other hand no compliance at all might cost a little traction under throttle over rough or uneven pavement (because tire loading is likely to vary more widely).

On the street and at the HPDE level at least, UCA bushing compliance provides a little cushion – a little extra margin against poo happening, that for most of us probably doesn’t cost much in terms of lap times. Driving style and personal preference are going to matter here, but if you’re starting from scratch with a stock/stockfish car it’s probably best to wait until you find something about the OE UCA design that’s clearly getting in your way before trying to “fix” it.


Norm
 
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but if you’re starting from scratch with a stock/stockfish car it’s probably best to wait until you find something about the OE UCA design that’s clearly getting in your way before trying to “fix” it.

Thanks @Norm Peterson, all valid points and certainly agree there is no one size fits all solution.

For me personally, I’m trying to solve an unpredictable snap-oversteer from mid to corner exit, which makes it very difficult to trust the car at optimal corner speed, and severely delays full throttle pick up. The key word here is unpredictable - which leads me to think it’s being caused by bind in the big poly bushing on the chassis end of the Whiteline UCA? Maybe ride height is low enough that I’m down on the bump stops, creating a non-progressive compression. One other thought is perhaps it’s the differential itself - still running the stock traction-lok, and perhaps it’s time for a Torsen. All 3 of these would lead to variation, and as you pointed out earlier in your post, none are able to be tuned as is. Important to note that on larger, less technical tracks like Big Willow and AutoClub Roval, the condition is far less inhibitive. On a tight, technical track like Chuckwalla, I had 17 turns to struggle through, which put me quite a bit slower than other cars that I would outpace on the 2 big tracks mentioned above.

I’ve decided to swap the UCA to the new style Whiteline with the Max-C bushing, along with the Steeda spherical bearing on the diff housing. Also swapping to the Ford Performance jounce bumpers at the same time, as mine are still stock and it’s a minor investment that should have been made when the car was lowered. I’ll run it this way to test, and then move on to the Torsen.
 
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Irvine, CA
Maybe ride height is low enough that I’m down on the bump stops, creating a non-progressive compression.
Also swapping to the Ford Performance jounce bumpers at the same time, as mine are still stock and it’s a minor investment that should have been made when the car was lowered. I’ll run it this way to test, and then move on to the Torsen.
I was definitely hitting the bump stops with just Steeda Boss springs which aren't that low, and I'm confident that was contributing to snap oversteer from mid-corner to corner exit like you're experiencing. I just cut down my stock bump stops and it has made a big improvement already. There could definitely still be other contributions in both our cases, but that was a quick and easy partial solution. Glad to see you're taking care of that as well.
FYI my UCA and PHB are stock, and my trailing arms are the 302R arms with urethane bushings.
 
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Quick update here - pressed the stock differential side bushing out today. Visible tears on both sides.

E9B36AE5-6AFA-4057-BA84-777F2D1138C6.jpeg93D15C90-CF3A-43A4-BFFF-101353090549.jpeg

FWIW, a little searching on e-Bay lead me to pieces of the Rotunda/OTC bushing tool that Ford specs in their service manual. Used 1/2”-20 threaded rod, old lug nuts and the Lisle 22800 stud installer. The bushing came right out without the impact even breaking a sweat. Also used it to press the new Steeda spherical bearing in where it worked just as well. Well worth the $50 to not have to mess with the hole saw, torch or other methods that seemed less than ideal.
86FDBDE9-66E8-4C82-82FE-F7BD6A881912.jpeg
 

drano38

Wayne
1,130
318
A couple years ago I replaced the Boss's UCA and diff bushing.
Did the Mecto UCA because it has a spherical ball in it to control binding. Our member Blacksheep mentioned he likes the design in several of his posts. Metco uses the same upper arm for 2005-2014. They simply change the mount's hole location for the '12+.
I used the BMR diff bushing, which goes into the stock housing (after using a hole saw to cut out the rubber out, and clean it up with a wire cup brush)
 

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