Rear end kick out - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 23 Old 06-25-2015, 02:01 PM Thread Starter
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Rear end kick out

Sorry about the title. I have an issue with my '91 on the rear. First, the parts: I have MM Extreme lower control arms, Ford M-5500A uppers, Koni Yellows (SA), Global West Race rear springs (don't know the rate). No torque arm or Panhard Bar.

When I go over a rough expansion gap or bump in curve especially, the rear end seems to kick out just a touch. Enough for me to be uncomfortable with. So with all of the new control arms, what could be going on?? I figured this was a locating problem? Thanks for any advice.


'91 LX 5.0 Daily Driver/AutoXer. Tremec 3550, MM RLCA, Panhard, Torque Arm, FLSC, STB and CC plates. Springs and Koni Yellow's. '03 Cobra brakes, rack, diff, Anniversary Cobra wheels. Justin
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post #2 of 23 Old 06-25-2015, 02:48 PM
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Sounds pretty normal for a stiff rear quadrabind to me. The durometer of those bushings is stiffer than stock per MM. Without a PHB, the rear end moves laterally enough to be scary. Back in the 90s, we videod a rear end moving during an auto-x and it scared everyone into selling their foxes and buying 3rd gen camaros.

Ford Mustang Rear Upper Control Arms, solid axle, 1979-04

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post #3 of 23 Old 06-25-2015, 04:47 PM
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Try loosening the rebound adjustment on the shocks
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post #4 of 23 Old 06-25-2015, 04:50 PM Thread Starter
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Thanks guys. I never figured it would be due to the stiffer bushings. I figured something was broken or starting to come apart (like my control arm bearings). Luckily, I have the MM PHB and I will be installing it, just don't know when.

MFE, I think I'm already a quarter turn from full soft. Does that sound right?

'91 LX 5.0 Daily Driver/AutoXer. Tremec 3550, MM RLCA, Panhard, Torque Arm, FLSC, STB and CC plates. Springs and Koni Yellow's. '03 Cobra brakes, rack, diff, Anniversary Cobra wheels. Justin
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post #5 of 23 Old 06-25-2015, 04:52 PM
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The correct answer is tonight hehe
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post #6 of 23 Old 06-25-2015, 07:19 PM Thread Starter
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Wait, what?! Is that from a song or something?

'91 LX 5.0 Daily Driver/AutoXer. Tremec 3550, MM RLCA, Panhard, Torque Arm, FLSC, STB and CC plates. Springs and Koni Yellow's. '03 Cobra brakes, rack, diff, Anniversary Cobra wheels. Justin
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post #7 of 23 Old 06-26-2015, 07:20 AM
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No, I mean get that PHB on there ASAP and go PM3L if you have the rear springs for it. Research your rear spring rates as well.
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post #8 of 23 Old 06-27-2015, 12:03 AM Thread Starter
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I'll see what the shocks are set on. No go on the rear springs though. I called Global West about year and half ago to ask about specific rates and all the rear springs are discontinued so he couldn't tell me what the rates were.

'91 LX 5.0 Daily Driver/AutoXer. Tremec 3550, MM RLCA, Panhard, Torque Arm, FLSC, STB and CC plates. Springs and Koni Yellow's. '03 Cobra brakes, rack, diff, Anniversary Cobra wheels. Justin
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post #9 of 23 Old 06-27-2015, 09:31 AM
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I believe if you measure the coil thickness, spring's free length, and the number of coils, you can manually work out the approximate rate. Do you have the part number?
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post #10 of 23 Old 06-27-2015, 01:23 PM Thread Starter
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They only have one part number anymore which is S-36 and I don't know if that's what mine are or not. I've looked but never seen a part number on them.

I found another site which was older info (from 2008) that said they were #160. The fronts are #800. I'll try to loosen the rear shocks some and see what that does. Thanks Casey.


'91 LX 5.0 Daily Driver/AutoXer. Tremec 3550, MM RLCA, Panhard, Torque Arm, FLSC, STB and CC plates. Springs and Koni Yellow's. '03 Cobra brakes, rack, diff, Anniversary Cobra wheels. Justin
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post #11 of 23 Old 06-27-2015, 07:32 PM
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Ok, well they are likely way too soft for TA or PM3L. You can still try to figure out the rate via the method above but I would just start looking for used TA springs here and on c-c. Usually go used for $60 or $80 a pair. Grab a pair of those and go PM3L, you can grab the spherical bushing and heim-jointed UCA for about $160 iirc.
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post #12 of 23 Old 06-29-2015, 12:44 PM Thread Starter
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I think I prefer to not run a PM3L. I thought that's what I wanted to do a couple of years ago but I know it places a significant amount of stress on the upper box. I would prefer to use the rubber bushinged Ford arm but I know the workload on it is doubled if not more and the bushings wear out fast.

I will probably do the MM torque arm when I can find a used one. People tend to hang on to those

On another note, I did loosen my rear shock all the way. They were both a quarter turn from full soft. I haven't driven it enough to tell much of a difference but I think I have noticed that it doesn't 'buckboard' or seesaw as much. Koni yellows may be a little too much for 160# springs but I wouldn't want to mismatch another color (red) on the rear.

'91 LX 5.0 Daily Driver/AutoXer. Tremec 3550, MM RLCA, Panhard, Torque Arm, FLSC, STB and CC plates. Springs and Koni Yellow's. '03 Cobra brakes, rack, diff, Anniversary Cobra wheels. Justin
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post #13 of 23 Old 06-29-2015, 01:05 PM
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I just installed a battle box on my p/s UCA torque box and all of the scary noises went away.

You can run yellows front and rears red, that's what I did for years before I went PM3L and jacked up the rear spring rates accordingly. You want the dampener to match the wheel rate, that is the main consideration.
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post #14 of 23 Old 06-29-2015, 06:39 PM Thread Starter
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Well I didn't know you could run two different colors like that. I do know when I bought the car it had SA Koni reds on it but talked to a MM tech several years ago and he recommended running the yellow. I guess the red is a better match for the rear with that 160#rate.

I do have a battle box kit in lower and upper. I don't remember the brand. I'm not too overly concerned about doing any damage to the upper but I know it's a possibility. Not to mention the NVH that transmits into the cabin.

What would be a good rear rate spring to go with the 800# front springs? With the quadrabind of course. I want to say that MM rear springs (Super Race) are stiffer than that.

'91 LX 5.0 Daily Driver/AutoXer. Tremec 3550, MM RLCA, Panhard, Torque Arm, FLSC, STB and CC plates. Springs and Koni Yellow's. '03 Cobra brakes, rack, diff, Anniversary Cobra wheels. Justin
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post #15 of 23 Old 06-29-2015, 08:42 PM
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I wouldn't mess with the spring rate until you move away from the quadrabind but, imo, you probably want as soft as possible in the rear, depending on the rear sway bar. I used to run 4-banger rear springs when I was quadrabind, no idea what rate those were. Had the C springs in my previous car, a convertible, no rate what those were either. It's all crap until you get rid of at least one rear upper control arm.
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post #16 of 23 Old 06-29-2015, 08:56 PM
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The problem is the binding uppers. Even with a PHB, so long as the uppers stay in place they will add wheel rate to the suspension until they bind at which point the rear will kick out. This is especially true if your spring rate is too high for the current suspension. It is imperative for you to learn the rear spring rate in order to find a workable solution.
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post #17 of 23 Old 07-02-2015, 01:05 PM Thread Starter
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Thanks guys. I've learned a lot by reading posts from you guys but I know there is much more to learn. Like I said before, I really wanted to do a PM3L about 2 years ago but I just don't know for a daily driver. I think I would rather bide my time and install the PHB with a MM torque arm.

Does anyone have a guess (approximately) what would be too high a spring rate for the rear with a good funtioning quadrabind? (that sounds like an oxymoron)

'91 LX 5.0 Daily Driver/AutoXer. Tremec 3550, MM RLCA, Panhard, Torque Arm, FLSC, STB and CC plates. Springs and Koni Yellow's. '03 Cobra brakes, rack, diff, Anniversary Cobra wheels. Justin
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post #18 of 23 Old 07-02-2015, 05:08 PM
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I ran my rod-ended PM3L on the street for nearly three years. Never suffered any failures or breakage. I will say that the single sheer fastener on the axle end required some regular checking, but nothing failed. It was noisy; lots of gear noise transferred into the cabin through the PM3L. Despite the noise, the system worked and transformed the handling characteristics of the car.
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post #19 of 23 Old 07-02-2015, 11:20 PM
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I too drive my rod ended, sperical beringed PM3L to events. Roads here are turrble though, would not daily. I don't really hear gear whine over everything else though (no sound deadening). Car is probably at least 3 seconds faster on 60 second auto-x course over quadrabind.
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post #20 of 23 Old 07-03-2015, 12:33 PM Thread Starter
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I drive about 30-35 miles a day. It's 30 round trip to work and 75% of that is interstate which is where the uneven expansion gaps are that tend to kick the rear out. So if I wasn't driving daily I probably would have gone PM3L by now.

An aside from that, I don't know how to make one and I don't want to have to buy two drag race adjustable type arms just to get one

'91 LX 5.0 Daily Driver/AutoXer. Tremec 3550, MM RLCA, Panhard, Torque Arm, FLSC, STB and CC plates. Springs and Koni Yellow's. '03 Cobra brakes, rack, diff, Anniversary Cobra wheels. Justin
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post #21 of 23 Old 07-03-2015, 12:59 PM
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I think I found the spring rates
Rear Coil Springs- Mustang
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post #22 of 23 Old 07-03-2015, 03:41 PM Thread Starter
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Quote:
Originally Posted by school boy View Post
I think I found the spring rates
Rear Coil Springs- Mustang
Thanks. I've seen that but couldn't make sense of the generic description. Unless they are saying something about the rate without directly stating the rate?

'91 LX 5.0 Daily Driver/AutoXer. Tremec 3550, MM RLCA, Panhard, Torque Arm, FLSC, STB and CC plates. Springs and Koni Yellow's. '03 Cobra brakes, rack, diff, Anniversary Cobra wheels. Justin
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post #23 of 23 Old 07-04-2015, 01:08 AM
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You can buy just one UCA and spherical bearing from Rear Suspension Product Categories these guys, I did. Then you just have to press out the stock axle-side bushing using MM's tool or similar.
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