Suspension question

jtl · May 8, 2011

I've got an 87 GT with stock suspension and I'm wondering what might fix what feels like lateral movement of the rear axle during cornering. It feels like the rear end sways to the side under cornering and if I quickly move the steering wheel back and forth at speed it feels like a slithering snake. I think the movement I'm feeling is in the rear but I'm not totally sure about that. I thought some urethane rear control arm bushings would help but then I've read that they can wreak havoc on the torque boxes, is that true? What about a panhard bar, would that help? Any help would be appreciated. Thanks!

Mustang5L5 · May 8, 2011

Go to the back pf your car and push the quarter panel above the rear end to rock the car side to side. Take a look at your rear rim, in relation to your fender lip. Does the rim move in and out? Or is the only side to side movement the tires sidewalk flex?

What side tires do you have on what size rims?

84Ttop · May 8, 2011

We are talking about 23 year old suspension here. I good upgrade to your stock suspension would be new upper and lower control arms with polyurethane bushings and well as new poly bushings in your rear housing. As far as torque boxes go, it depends on your driving style and how hard you are on this car. they are pretty tough and will hold up to some abuse; however, slicks or even drag radials and racing in general can and will destroy your torque boxes. Don't worry, they sell re inforcment kits that can be installed in a matter of a weekend but it ultimately depends on you and your driving style. As far as a pan hard bar, I have never seen the need on a fox to install one, then again I've only drag raced, not auto crossed I can't see where there would be harm in having one, just don't think it's necessary.

stang&2Birds · May 8, 2011

jtl said:
I thought some urethane rear control arm bushings would help but then I've read that they can wreak havoc on the torque boxes, is that true?

A stock LCA can (and often does) ruin the torque boxes. So, any "upgrade" to the rear suspension will put more force on the torque boxes, and greatly increase the chance of them ripping the **** out from the body.

IMHO, the first rear suspension upgrade MUST be to the torque boxes. I like the Battle Boxes - very heavy metal, great kit!

jtl said:
What about a panhard bar, would that help? Any help would be appreciated.

Panhard bars are nice. But, have you read the MM instructions? To do it correctly, it gets involved. Also, for a street, a Panhard bar may be an overkill. But, I know how some curves and on/off ramps are. Otherwise, it is hard to justify the need for a panhard bar for driving safely on the streets.

Also, unless you have sub-frames, that's the first thing to do before any suspension upgrades. Fox Stangs have MEGA POS uni-body frames that have very poor stiffness and resonance frequency. I doubt that even the cheapest car made today has a frame that is worse than the Fox.

Good Luck!

reldla1996 · May 8, 2011

Lateral motion of the rear factory suspension on a Fox Mustang is mainly controlled by the rear upper control arms. I would look there first. The rear upper control arms do not bolt to the torque boxes, so you're not worried about those with this problem. A panhard bar will control lateral motion, but can introduce other issues. As Mustang5L5 suggested, have someone push sideways on the rear quarters while you look underneath to see what is moving. Unless you're going to convert to a new style suspension, e.g. torque arm, you should fix your existing problem before you introduce new elements like a panhard bar.

jtl · May 9, 2011

Mustang5L5 said:
Go to the back pf your car and push the quarter panel above the rear end to rock the car side to side. Take a look at your rear rim, in relation to your fender lip. Does the rim move in and out? Or is the only side to side movement the tires sidewalk flex?

What side tires do you have on what size rims?

That's a good idea. I will try that. For tires and wheels I'm running 225/50/16's on pony wheels.

Thanks for your input everyone!

MFE92 · May 9, 2011

Yes, the rear upper control arms DO bolt to torque boxes...the upper ones.

New FRPP uppers with new bushings for the differential end (sold separately) would probably make it feel like a new car. If you want to eliminate that slop altogether, spring for a panhard bar

Sharad · May 10, 2011

An upper and lower control arm kit like this one from UPR Products will dramatically reduce the slop in your rear axle's movement: 79-98 Mustang Elite Chrome Moly Urethane Control Arm Suspension Kit

The control arms are tubular chrome-moly with polyurethane bushings so they are very durable, and they have a lifetime guarantee.

If your torque boxes are damaged they can be repaired, here is the kit to reinforce them: 79-04 Mustang Heavy Duty Upper/Lower Torque Box Kit

Mustang5L5 · May 10, 2011

With as fragile as the torque boxes are, in unreinforced state, i'd stick strictly with rubber bushings in the upper arms. Ford Racing HD arms and new rubber bushings are all that is needed there for most street driven applications

Of course...identify the problem first. It doesn't make sense to throw nice new expensive parts at an issue without at least trying to attempt to discover why you are having a problem.

$600+ in new control arms is not going to do you any good when you crawl under there and find a torque box is tearing out.

jtl · May 10, 2011

Mustang5L5 said:
With as fragile as the torque boxes are, in unreinforced state, i'd stick strictly with rubber bushings in the upper arms. Ford Racing HD arms and new rubber bushings are all that is needed there for most street driven applications

Of course...identify the problem first. It doesn't make sense to throw nice new expensive parts at an issue without at least trying to attempt to discover why you are having a problem.

$600+ in new control arms is not going to do you any good when you crawl under there and find a torque box is tearing out.

I know the Torque Boxes are OK right now but I would like to reinforce them in the future. I'll never have anything but street tires on this car so I think I can hold out for a little while. In the meantime I may install some urethane bushings in the axle housing end and maybe reinforce the stock control arms to see if that helps.

Suspension question

jtl

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Mustang5L5

That is…until I whipped out my Bissell

84Ttop

They make new pistons every day, so why worry?

stang&2Birds

reldla1996

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jtl

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MFE92

Sharad

ALWAYS choose the V over the P!!! Wait... what?

Mustang5L5

That is…until I whipped out my Bissell

jtl

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