When I hit the gas, my car pulls to the right... As soon as I get off the gas, it makes a dramatic correction and almost throws me into on-coming traffic... Even when I accelerate slightly, I can feel it... What should I check?
What is loose? Torque steer?!
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trinity_gt
10 Year Member
I'd start with the rear suspension: control arms, mounts/torque boxes etc. This sort of thing might happen if the rear axle is moving excessively in response to torque inputs from the driveshaft due to broken or damaged links back there.
Has the car been raced/abused (e.g. drag raced with slicks and hard launches etc)? Are the components in the rear suspension stock or aftermarket?
Upper and Lower control arms have been replaced "MAC". Eiback Pro-kit springs and shocks.. Everything else is stock... I did replace the gear with a 3:73 (ring / pinion), but otherwise, no changes... It seems to be getting worse as I drive more and more... We removed the quad shocks as well...
The car has been sitting in my garage for over a year and I just started driving it again... I did race the car a few times with drag radials, but didn't hear anything break or loosen...
The car has been sitting in my garage for over a year and I just started driving it again... I did race the car a few times with drag radials, but didn't hear anything break or loosen...
wmburns
SN Certified Technician
Quad shocks dampen axle torque yaw
Sooooo. You don't think the removal of the quad shocks might have something to do with this??????
The quad shocks dampen the left to right yaw of the rear end. Without the quad shocks, the rear end is free yaw and place additional wear on the bushings. I suspect the bushings have worn. Now the rear end is loose enough to yaw to the point of a problem.
Sooooo. You don't think the removal of the quad shocks might have something to do with this??????
The quad shocks dampen the left to right yaw of the rear end. Without the quad shocks, the rear end is free yaw and place additional wear on the bushings. I suspect the bushings have worn. Now the rear end is loose enough to yaw to the point of a problem.
My mechanic advised me that the quad shocks won't cause that dramatic of a "push / pull" during on/off accelleration, but I think your right... I'll bet since he removed them (not sure why), it put that additional side-to-side stress on the control arm bushings and wore them out... I'm going to look at them today...
Thanks guys!
Thanks guys!
trinity_gt
10 Year Member
Clarification: The quad shocks are there to dampen fore-aft motion of the rear axle on each side and are needed because the front bushings are so soft and pliant -- as they need to be to allow the 4-link to operate over its range of motion without binding.
If you've replaced the control arms with, say, Mac parts like these:
you don't really need the quad shocks because the front bushings are so stiff. But that raises another problem: binding. The control arms at the back are fixed at both ends to what are effectively rigid bodies. The uppers and lowers swing in different planes and being different lengths, they travel in very different arcs. Without compliance in the bushings to allow for these rigid arms fixed to rigid bodies at either end to swing through different planes and arc radii, you'll get binding and worse, you can put excessive stresses on the arm mounting points. You'll not likely hurt the lower control arm mounts in the frame nor the mounts on the axle. It's almost always the upper mounts on the body that get hurt because of binding. Add in the stress of drag radial launches at the strip and you may well be looking at upper control arm mounts tearing away from the floor pan. Since the upper arms are primarly the ones that give side-to-side axle location under the car, if they're going away you can get odd geometry changes in the back when you apply torque that can make the car rear-steer and be dangerous...
Get it up in the air and carefully check the upper mounts for tears in the brackets, broken spot welds and the like.
If you've replaced the control arms with, say, Mac parts like these:
you don't really need the quad shocks because the front bushings are so stiff. But that raises another problem: binding. The control arms at the back are fixed at both ends to what are effectively rigid bodies. The uppers and lowers swing in different planes and being different lengths, they travel in very different arcs. Without compliance in the bushings to allow for these rigid arms fixed to rigid bodies at either end to swing through different planes and arc radii, you'll get binding and worse, you can put excessive stresses on the arm mounting points. You'll not likely hurt the lower control arm mounts in the frame nor the mounts on the axle. It's almost always the upper mounts on the body that get hurt because of binding. Add in the stress of drag radial launches at the strip and you may well be looking at upper control arm mounts tearing away from the floor pan. Since the upper arms are primarly the ones that give side-to-side axle location under the car, if they're going away you can get odd geometry changes in the back when you apply torque that can make the car rear-steer and be dangerous...
Get it up in the air and carefully check the upper mounts for tears in the brackets, broken spot welds and the like.
trinity... Awesome exlpanation and it totally makes sense... I am going to head over to my shop this weekend and throw it on the lift. I'll let everyone know my results... The car definitely has rear-steer under accelleration and then snaps back when releasing the gas. With the amount of power I have, there is now way I can safely open it up without heading into on-coming traffic. So, something in the rear suspension is not right. I hope to find my answer this weekend.
If it is the upper control arm bushings that bound, would you replace the bushings, or would it be less work just to replace the entire control arm?
Also, do you know if it's a common issue with MAC control arms that the bushings go so quickly. I don't even have 6,000 miles on these arms. Yet I made about 15 runs at the track with them. About 10 with Drag Radials...
If it is the upper control arm bushings that bound, would you replace the bushings, or would it be less work just to replace the entire control arm?
Also, do you know if it's a common issue with MAC control arms that the bushings go so quickly. I don't even have 6,000 miles on these arms. Yet I made about 15 runs at the track with them. About 10 with Drag Radials...
trombonedemon
Well-Known Member
Damn good explanation, I was gonna take mine off until I read your post. They are squeaky as a hundred mice, guess they need to be replaced.Clarification: The quad shocks are there to dampen fore-aft motion of the rear axle on each side and are needed because the front bushings are so soft and pliant -- as they need to be to allow the 4-link to operate over its range of motion without binding.
If you've replaced the control arms with, say, Mac parts like these:
you don't really need the quad shocks because the front bushings are so stiff. But that raises another problem: binding. The control arms at the back are fixed at both ends to what are effectively rigid bodies. The uppers and lowers swing in different planes and being different lengths, they travel in very different arcs. Without compliance in the bushings to allow for these rigid arms fixed to rigid bodies at either end to swing through different planes and arc radii, you'll get binding and worse, you can put excessive stresses on the arm mounting points. You'll not likely hurt the lower control arm mounts in the frame nor the mounts on the axle. It's almost always the upper mounts on the body that get hurt because of binding. Add in the stress of drag radial launches at the strip and you may well be looking at upper control arm mounts tearing away from the floor pan. Since the upper arms are primarly the ones that give side-to-side axle location under the car, if they're going away you can get odd geometry changes in the back when you apply torque that can make the car rear-steer and be dangerous...
Get it up in the air and carefully check the upper mounts for tears in the brackets, broken spot welds and the like.
Well I just got the car off the lift and discovered some distubing damage! All of my bushings are shot! The lower control arm bushings took it the worst. One of them is actually in half. The other one is close to gone too. The upper control arm bushings are in the best shape, but they are on their way out. So, what do I do? Am I able to get replacement bushings for my MAC control arms? Or should I research a new set of uppers and lowers? Possibly change to a torque arm setup?? Any advice on where to go from here? It's clear that the MAC control arm bushings can't handle the power I have. I need something better. Thanks!!
trombonedemon
Well-Known Member
I have had this problem with my mac control arms as well. I have replaced the bushings 3 times over the few years i have had them. I would go with different control arms. You can order new bushings from mac as well but this might not be the last time you have to replace them.
I've had the control arms for about 2,000 miles and about 15 runs at the track. I don't think the bushings can handle the 500 hp I'm throwing at them. For cost reasons, I'm going to order just the bushings for now. However, I'm probably going to switch up to the MM XD lowers as they are rating at high torque / HP once I get the fundage.
Anyone know where I can find the MAC bushings? I've searched, but can't find anyplace that has them.
Anyone know where I can find the MAC bushings? I've searched, but can't find anyplace that has them.
twogts4us
15 Year Member
It's what you call rear-wheel torque steer. That's what you get when you break stuff... It's the wierdest feeling EVER when the rear of the car steers and your car starts to "crab walk"....
I've got all kinds of terms you never hear of...
I've got all kinds of terms you never hear of...
I know the crab walk feeling that you're talking about. It's pretty scary at times! That's why I bought these bad boys!
twogts4us
15 Year Member
Yeah when you break something I could see the car crab walking...or when a car has had it's frame/suspension so bent that it can no longer trac straight...I know what crab walking is. But still don't equate that to rear wheel torque steer. I could make up a term and call it whatever I like too...but it doesn't make it accurate. (I've got all kinds of terms you never hear of too)
Shiroelex - nice pics, nice parts...I'm jealous.
Shiroelex - nice pics, nice parts...I'm jealous.
What is your main purpose for the adjustable control arms. I'm just trying to find the value in getting those. That is almost the exact setup that I am going to buy once I get the cash.
I bought those exact ones because I hit the strip often, and run slicks occasionally. I like my car slammed when cruising, and wanted the adjustable spring perches so I could crank the rear end up to run tall slicks. On a set of stock 'stang springs and the perches all the way up, I cleared a 28x10x15 slick with no issues. I liked the extreme duty arms because they have spherical bushings on either end of the arm as well. The only downside I've found with them is that they have a tendency to chirp on rough terrain. I just need to get my fatass back under the car to grease them up again. Here's a shot of the car with them at about 3/4 of the way down. It can go lower in the back than this!
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