1997 Mustang Convertible GT Rear End Not Compressing

Happster

New Member
May 30, 2010
14
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1
Dunstable, MA
So here's a new one. I did a complete restoration on a 97 GT convertible. When putting the rear end/suspension back together I used the stock rear end and springs, but put in upper and lower torque box reinforcements and tubular control arms. The reinforcements do not rest inside the boxes and can in no way interfere with the mechanics and operation of the control arms.. I also bought new shocks and quarter shocks. I have yet to put the interior, doors, trunk and roof back on the car. When I dropped it to the ground after getting it all together (without torquing the control arms) the suspension did not compress at all. There is about 8 inches of clearance between the tires and fender well. Saying it is "hung up" is not technically correct, hung down us more accurate. It is not compressing into normal range. It looks like something out of the 70's. Actually looks kind of cool, but wouldn't do for performance.

Given that I still have about 400 lbs. of parts to put back on, a couple friends and I stood on the rear bumper and jumped up and down...hardly budged, even with every control arm bolts only hand tight.

What else I've done thus far:

-checked the orientation and seating of the springs. They are fully seated and the pig tails on the lower ends are both pointing driver's side. I know that to be correct.

-checked the size and functionality of the new shocks. They are correct and I can compress them by hand.

-checked the specs on the aftermarket control arms - they are identical to the stock ones in every way. As noted, they are not torqued down or even tightened. I will say that they were hard to install...tough to get bolt holes to line up. But I recall that always being the case when putting control arms in. Just need to move the axle around.

-took out ONLY the springs, bolted it back together, and compressed the axle all the way up to the rubber stopper with a floor jack under the differential, no problem. Thus ruled out binding of the control arms or any similar mechanical obstruction.

-put the springs back in, same problem.

So it has to be the springs, but how? They are the stock springs with 90k miles on them that came out of this very car. When I got the donor car, there was the typical 1 inch of clearance between the tires and the fender well. Now I have 8 inches with the same body, the same springs and the same rear end. I can see the springs needing to settle a little after being removed and fully extended on my garage floor for a few months, but this is ridiculous. I'm stumped. Thoughts on what it might be, tests I can perform, etc., appreciated.
 
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Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
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Did you torque the control arms with the rear end dropped, or did you put stands under the rear, let it rest at ride height and then torque?
 

Happster

New Member
May 30, 2010
14
0
1
Dunstable, MA
Did you torque the control arms with the rear end dropped, or did you put stands under the rear, let it rest at ride height and then torque?
I did initially then remembered that they need to be torqued under load. Never put weight on it before realizing my error and loosening the bolts. No damage to torque boxes, bushings, or control arms. The torque boxes sprang right back out when I loosened the bolts.
 

Happster

New Member
May 30, 2010
14
0
1
Dunstable, MA
After reading another post I'm thinking it's the upper arms. They should not have been that tough to line up. Still welcome thoughts while I remove them, see if it settles and check alignment at normal ride height.