Why NOT to use boxed rear UCA on the street.

Topic: Why NOT to use boxed rear UCA on the street. (Read 4047 times) previous topic - next topic

Why NOT to use boxed rear UCA on the street.

February 23, 2017, 10:36:22 PM

Found what all the noise was...

Why NOT to use boxed rear UCA on the street.

Reply #1 – February 23, 2017, 11:21:39 PM

I never had an issue, personally.

How old was that bushing? The boxed arms will put more stress on the rubber bushings, but they will give. If it was poly, then replace it with rubber, and be on your way.

Why NOT to use boxed rear UCA on the street.

Reply #2 – February 24, 2017, 01:49:34 AM

I thought the upper arms were supposed to flex some.

Why NOT to use boxed rear UCA on the street.

Reply #3 – February 24, 2017, 08:00:05 AM

The stockers do flex some. I never had an issue with boxed or AM arms and rubber bushings on the axle.

Why NOT to use boxed rear UCA on the street.

Reply #4 – February 24, 2017, 11:18:05 AM

I removed the arms and cut off the plates I used to box them in. They cleaned up to the point that you couldn't tell anything was done to them. Luckily they were in excellent condition to start with as they are hard to come by. They should flex now! The contributing factor to this mess was when I had the 4.10s put into this spare housing out of the car for ease of work,the guy put in poly bushings in the stock shells. I didn't know this at the time. Since I didn't have the bushing removal tool, I just put a spare set of poly bushings back in for now to see what happens. The arms still have rubber in the front so it's a start.

Why NOT to use boxed rear UCA on the street.

Reply #5 – February 24, 2017, 12:02:27 PM

Yeah, it looked like a toasted poly bushing.

I ran these in a couple cars with rubber on the axle for a while. No issues.

Why NOT to use boxed rear UCA on the street.

Reply #6 – February 24, 2017, 12:27:51 PM

So, in that application, the rubber has to take more abuse due to the fact that there is no flex or twisting like the stock arms?

Why NOT to use boxed rear UCA on the street.

Reply #7 – February 24, 2017, 03:08:12 PM

In the std splayed 4-link Fox rear suspension, those flimsy upper arms are what keeps (or tries to keep) the rear end centered under the car.

Why NOT to use boxed rear UCA on the street.

Reply #8 – February 24, 2017, 04:07:45 PM

FWIW Jack from Maximum Motorsports told me to only run the stock, stamped, upper control arms with rubber bushings with any aftermarket control arm (my Thunderbird has Maximum Motorsports extreme duty lower rear arms with spherical bushings). The stock upper arms flex around and twist. If you get rid of that range of movement from the upper arms combined with stiff lower arms you can have odd steering issues or, as you've seen, damage the upper arms. Basically the it goes from good, better, to best: stock upper arms and aftermarket lower arms; stock upper arms, aftermarket lower arms, panhard bar; stock upper arms, aftermarket lower arms, panhard bar, torque arm.

Also I really want to install a Maximum Motorsports panhard bar at some point.

Why NOT to use boxed rear UCA on the street.

Reply #9 – February 24, 2017, 10:08:33 PM

Yeah, Jack knows what he's talking about, but on the street, the average person isn't going to be pushing the car that far for it to make a difference. HP driving events, cone smashing, canyon carving. That's where you have the car at the limits and these things all come into play, and all the deficiencies of the stock Fox rear suspension rear their ugly head.

I drove the out of the car that had those uppers on it (On the street, admittedly) and I had the unpardonable poly-bushed/boxed lower stock arms (It was a LOOONG time ago) with rubber bushings in the axle. Never encountered any pucker-inducing problems. Replaced the rubber bushings once or twice, but that's it.

For street use, what the OP is doing is fine.

Why NOT to use boxed rear UCA on the street.

Reply #10 – February 25, 2017, 12:25:18 AM

Im actually terrified of how the rear suspension works after my 88xr7.

Car had bad shocks, and bad brakes. I saw the brakes as a much bigger deal, as I have had quite a few cars with worn shocks. After fixing and bleeding the brakes, I went out to test them on a dirt road so I could see if they were all locking up evenly. First time I did it the car swerved hard right. Same thing second time. Looking at the skid marks, it looked like the car was turning.

I figured I must have trapped air somehwere, so I went back to bleeding them. Next time, same thing happened, car swerved hard right, but this time only under moderate braking. I explained it to my dad, and he said that doesnt make sense, take me for a ride. I went out to a lonely to lane road at the end of town, and when I hit the brakes, I was ready to swerve expecting the car to go right, instead it went left, off the road, into a grass feild.

The next morning I drove out and looked at the skid marks, the rear axle turned, did a 90° turn with my skid marks in two car lengths at 40mph.

Sure the bushings were shot or something was broken, I crawled under there to find the rear end had been replaced, and half the bolts were loose and were tightened with no weight on the suspension. I loosed all the bolts, set the axle on a jack to load it and torqued them all down. Now it didnt swerve as suddenly, but was still really unpredictable.

Finally, I decided the shocks were too bad to ignore. I was sitting in the car and a cat jumped on the trunk and it rocked the car hard enough it scared me. So I swapped them out. Pulled the old rusty used ones off my 86 just hoping it could make any sort of difference, and instantly it was fixed.

Why NOT to use boxed rear UCA on the street.

Reply #11 – February 25, 2017, 12:31:56 AM

Quote from: Chuck W;459459

Yeah, Jack knows what he's talking about, but on the street, the average person isn't going to be pushing the car that far for it to make a difference. HP driving events, cone smashing, canyon carving. That's where you have the car at the limits and these things all come into play, and all the deficiencies of the stock Fox rear suspension rear their ugly head.

I drove the out of the car that had those uppers on it (On the street, admittedly) and I had the unpardonable poly-bushed/boxed lower stock arms (It was a LOOONG time ago) with rubber bushings in the axle. Never encountered any pucker-inducing problems. Replaced the rubber bushings once or twice, but that's it.

For street use, what the OP is doing is fine.

More than likely yes, the average person won't have any issues on the street. In my case with spherical bushings on both ends of the lower control arms poly in the uppers was going to be over kill.

I wonder if hard launches contributed to the poly failure? The power+weight may have been too much for them to handle. Since poly is stiffer it will sheer, instead of flex like rubber.

Why NOT to use boxed rear UCA on the street.

Reply #12 – February 27, 2017, 09:29:42 AM

From what I understand, had on my car, and currently have on my car the list is:

Stock upper arms and aftermarket lower arms - Huge improvement over the stock stuff due to the reduction in flex of the lowers.
After market uppers and lowers - Vast improvement over the stock uppers when following the manufacturer's instructions. GM A-Body uppers work on our cars as well as the CHE units and for some are necessary to dial pinion angle in when lowered.
Stock upper arm(s), aftermarket lower arms, panhard bar - The panhard bar is what is locating the rear under the car from side to side so you do not absolutely need both upper control arms, just one to keep the pinion angle. MM will not tell you to remove one but Griggs will. The trick here is that when you remove one UCA you remove the bind but in doing so you will need stiffer springs in the rear to compensate for the loss of the bind which had an induced spring rate. I ran my Coupe for three years on the street with only one UCA but I was looking to kill Camaros at all costs back then. Running both UCA's will mandate the use of rubber bushings on both ends or you will FUBAR up any benefit of the panhard bar. I actually think this would make things worse than without the panhard bar.
Aftermarket lower arms, panhard bar, torque arm - With the addition of the torque arm there is no need for the upper control arms as it sets and keeps the pinion angle and moves the instant center of the car to a more desirable location.

Why NOT to use boxed rear UCA on the street.

Reply #13 – February 27, 2017, 02:03:33 PM

I plan on adding the Maximum Motorsports panhard bar to the Maximum Motorsports lower rear arm/stock upper rear arm combo I'm running. I may try to get around to it this summer.

Why NOT to use boxed rear UCA on the street.

Reply #14 – February 27, 2017, 08:18:36 PM

Had some time to play with the car today after an extensive dist re-curve and found that after the UCA mods, the car rode better BUT noticed a blip of wheel hop. The car lauches hard in second with one quick hop. Since it's a street ride all is good.