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Topic: Left Rear Sagging on 87 Tbird, Mechanic Thinks Right Frt Control Arm Bent (Read 5821 times) previous topic - next topic

Left Rear Sagging on 87 Tbird, Mechanic Thinks Right Frt Control Arm Bent

On my 87 T-bird the left rear of the car sags 1-1/4" compared to the right rear. I've disassembled the entire rear suspension and have found no visible damage or other problem. I've even switched rear springs side to side. Did this thinking that if the left rear spring was weak then when switched the right rear would sag. After the switch there was no difference in the measurements. So I've taken the car to a professional mechanic and he raised the car in the air on his hoist to get a better look under the car. Only thing the mechanic found was that maybe the right front lower control arm was twisted. But he was not really sure since the spring pocket on the left control arm protruded about 1/4" more beyond the under side of the control arm than the left front control arm. The twist he also found was by using a Level and placing it on the on the under side of the control arms and parallel to the tires. The result was the under side of the left control arm was level with the ground with the spring cup was just barely lower that the lips of the control arm. On the right front control arm it was far from being level to the ground and the spring cup protruded about 1/4" lower than that of the left control arm.

My question is there a difference in the shapes of the front lower control arms on an 87 T-bird or is this right control arm twisted or damaged some how?


Left Rear Sagging on 87 Tbird, Mechanic Thinks Right Frt Control Arm Bent

Reply #2
A problem in front that would effect the rear by 1¼" should be obvious...

Jack up the LF and see how much you have to raise it to lower the RR by 1¼"...

Left Rear Sagging on 87 Tbird, Mechanic Thinks Right Frt Control Arm Bent

Reply #3
Aren't the Turbo Coupe front control arms different from the standard control arms?  Could someone have replaced and mixed/matched parts?

Left Rear Sagging on 87 Tbird, Mechanic Thinks Right Frt Control Arm Bent

Reply #4
No difference.

I agree, busted spring. If there was a pothole or other contact hard enough to tweak a c/a, there's going to be lots of other broken stuff.

One question....any rust on the car? ANY rust?

The front springs are notorious for rusting and breaking...causes all sorts of silly shiznit..
'98 Explorer 5.0
'20 Malibu (I know, Chevy, but, 35MPG. Let's go brandon, eh)

Left Rear Sagging on 87 Tbird, Mechanic Thinks Right Frt Control Arm Bent

Reply #5
Quote from: TurboCoupe50;457495
A problem in front that would effect the rear by 1¼" should be obvious...

Jack up the LF and see how much you have to raise it to lower the RR by 1¼"...

Good suggestion!

Made the following measurements with the car at a normal rest on level ground going from the wheel well lip down past the center of the wheel to the ground.
Results were:
LF = 27.50"  RF = 27.50"
LR = 27.25"  RR = 28.75"  rear side to side difference = 1.50"

Then placed jack under LF control arm spring pocket and proceed to raise LF of car.
Results were:
LF = 30.75"  RF = 28.75"  front side to side difference = 1.50"
LR = 28.00"  RR = 28.00"

From these measurements does the LR sag or is the RR to high?

I'm the original owner of the car as are the front control arms are original and frt springs. I don't recall ever hitting a pothole.

Left Rear Sagging on 87 Tbird, Mechanic Thinks Right Frt Control Arm Bent

Reply #6
If front spring was broken there would likely be a noticable difference between RF& LF...


I want to say the 27.5" is approx correct but can't remember height of mine, I know it's approx 1/4"-3/8" lower in front than one with orig engine...

I believe I've posted height of my Bird in past, maybe a search will find that info...

Left Rear Sagging on 87 Tbird, Mechanic Thinks Right Frt Control Arm Bent

Reply #7
I'm wondering if the rear end axle housing could be bent? You could check by hanging some string lines across the back and the top or bottom from hub to hub. Check dimensions from the string line to the axle tubes at various locations. If they are not consistent, that could be where the problem lies.

Left Rear Sagging on 87 Tbird, Mechanic Thinks Right Frt Control Arm Bent

Reply #8
So this is a very common problem in the Fox Mustangs so we can learn a lot from them being the chassis are very similar.  There was a TSB on the Mustangs addressing this pointing to the driver side front spring softening and requiring replacement.  I know a lot of guys that replaced all four springs and the problem persisted but thought the TSB was interesting so here it is:

90ford47
 SPRINGS - VEHICLE LEAN - APPLICATION CHARTS - EXCLUDES "SALEEN" MODELS
 Article No. 90-26-3
 FORD: 1989-90 MUSTANG
 ISSUE: Vehicles may have a tendency to lean to the left because the location of the battery, windshield washer bottle, radiator expansion bottle and engine accessory drive may cause a weight bias on the left front side. This lean condition most often appears as a lean in the rear of the vehicle rather than the front.

ACTION: Check the wheel lip measurement and, if required, install a new left front spring to restore the vehicle to a more level attitude. The front spring is to be changed, even if the lean is greater in the rear of the vehicle. Refer to the following procedure for service details.
 Figure 1

 1. Place the vehicle on level ground.

 2. Take all measurements from the ground to the body wheel lips as close to the axle center line as possible, Figure 1.

 3. Determine the difference of the front wheel lip measurements by substracting the low from the high measurement. Using the following Wheel Lip Measurement Chart. select the correct spring load change (i.e. plus 1. plus 2) within the rate group.

 4. After determining the correct spring change (i.e. plus 1 or plus 2) find the three letter tape code located on the front spring of the side that exhibits the lean and select the replacement spring using the following charts.


 The following 1989-1990 Mustang Rear Spring Chart is provided for general informational purposes only. Generally, the rear springs will not have to be replaced unless there is damage or structural concerns.

 (*) Code is also in Parts Book.

 5. Remeasure the vehicle as described in Steps 1 and 2. Confirm that the vehicle is in specification per the Wheel Lip Measurement Chart. If the vehicle is not to specification (0.00" +/- 0.20"), repeat Step 3 through 5.

Within a rate group, installing a high load spring will increase the vehicle ride height. Conversely, a lower load spring will decrease the vehicle ride height. The following Spring Change Bumper Effect Chart indicates an approximate change in bumper-to-ground height for each increment of spring change.

 OTHER APPLICABLE ARTICLES: None

 WARRANTY STATUS: Eligible Under Basic Warranty Coverage
 OPERATION DESCRIPTION TIME
 902603A Replace Spring 1.2 Hr.
 DEALER CODING
 BASIC PART NO. CONDITION CODE
 5310 63
 OASIS CODES: 304000

83 351W TKO'd T-Bird on the bottle


93 331 Mustang Coupe - 368 rwhp

Left Rear Sagging on 87 Tbird, Mechanic Thinks Right Frt Control Arm Bent

Reply #9
Wanted to break this up into a couple of posts as that TSB is long.  Other issue found were worn control arm bushings both front and rear, tweaked chassis (this was a bitch if you had already welded in SFC's), tweaked control arms, bent axle housing, etc.  One guy completely rebuilt the suspension in his Fox Mustang and had the chassis checked on a frame machine and still had about 1/2" or so of sag.  He ended up adjusting it out with the coil overs on the car.  Needless to say these cars were not built with the tolerances we have now and that is still not saying much.

So check the basics and if they are all good then it may need to go to a body shop and up on a frame machine.

83 351W TKO'd T-Bird on the bottle


93 331 Mustang Coupe - 368 rwhp

Left Rear Sagging on 87 Tbird, Mechanic Thinks Right Frt Control Arm Bent

Reply #10
Quote from: Aerocoupe;457532
So check the basics and if they are all good then it may need to go to a body shop and up on a frame machine.


From my earlier investigations I knew that both of the KYB front struts had lost gas pressure. They may even be worn out since they both slowly collapse under the weight of the upper strut mount when they were unbolted from the strut tower. So after removing the brake caliper and rotor and with the sun shinning at just the right angle today I could see that the LF spring was indeed broken. Had a heck of a time removing the two lower bolts on both of the struts. I guess the heat from the Ft brakes really seizes those bolts. Anyway both front springs were broken. LF was broken at about 7/8 of a coil and remainder of spring measured 14-3/8" long. RF was broken at about 3/4 of a coil and remainder of spring measured 14-5/8" long. With both Ft springs broken at roughly the same length that would explain why there was no visible lean observed on the front of the car. Another side benefit of the broken springs is this had the same effect as having  lowering springs in the front. This would also explained why the Ft fender/tire gap measurements on my car is roughly the same as other T-Birds which have lowering springs.

But, even with the car supported by jack stands under the front frame rails at the same point from side-to-side and with the RR shock disconnected ( thinking that its gas pressure was raising the RR ) the RR was still much higher than the LR. So the chassis is probably twisted and in my case it's 1-1/4" to 1-1/2". So I'll have to get my local body guy to measure the frame when car is back together.

I have a question about the reliability of these broken Ft springs. If I was to square-off the ends of both springs so they'd be the same length. Could I use these springs the same as if I were to buy new lowering springs? I'm guessing the only reason why the Ft springs break on these Fox Body cars is because of the way the Ft control arms are designed. The same could happen to new replacement springs.

Quote
TSB Information


From this TSB I guess you could tweak the frame measurements. That is if you still had the Tag codes and if you could buy just the right spring.

Left Rear Sagging on 87 Tbird, Mechanic Thinks Right Frt Control Arm Bent

Reply #11
This is the cars original LF spring now broken.
X
And this is the cars original RF spring also now broken.
X


Left Rear Sagging on 87 Tbird, Mechanic Thinks Right Frt Control Arm Bent

Reply #13
The reason those springs broke is that they are not made well. Swap over to the SN95 springs and get some quality dampers on all four corners. Check all of the control arm bushings, sway bar frame mounts & end links, and ball joints.

If you install the new springs I would highly recommend you get the Maximum Motorsporte caster camber plates. Once you have installed all the new parts and have an alignment done see where you are at with the gangster lean in the rear. Let the springs settle a day or so before getting the alignment.

If you replace the front lower control arm bushings remember to torque the bolts only with the suspension fully loaded or you will preload them and they will prematurely wear out and cause the front of the car to be higher than it should be. Also, the strut mount bolts to the spindle have crimped nuts which make them difficult to get off.

83 351W TKO'd T-Bird on the bottle


93 331 Mustang Coupe - 368 rwhp

Left Rear Sagging on 87 Tbird, Mechanic Thinks Right Frt Control Arm Bent

Reply #14
Any updates on this fix, 87tbird?  My car has this same issue, so I am interested to hear if you found a solution.