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Discussion Starter #1
My father in law has a 68' gt mustang fast back 4 link car that has a wicked deceleration side to side wobble, let me know your thoughts on where to start figuring out what the problem could be, don't need the ol man getting hurt,, ill answer all the questions you have and get more info if needed. Here is the car... Thanks for any and all comments and help.. I'm thinking its something in the 4 link but I'm not versed as much as I should be with this set up, does not have arb... Thanks again...-SL



 

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Bump steer or maybe excessive preload in the 4 link could do that. Was it good and suddenly got bad or has it just progressed slowly or what?
 

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Discussion Starter #3
Was good and got bad, went through all the shock settings, tire pressure front and rear etc... We won the race but still, cars not right
 

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Check the u-joints.also did you make any rear suspension changes lately? Could the pinion angle have changed? have you checked all the front suspension component for wear?
 

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check your heim joints and the wish bone just my thoughts have had them go bad and created the same problem for me put new joints in the four bars and wish bone and solved my problem good luck killer70 nova
 

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aka hulk
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sounds like maybe corner weights are shifting on decel,..like when you lift going through the traps,...maybe too much spring preload on rear shocks?
 

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Discussion Starter #9
Thanks for the input, we will start checking it this weekend and ill post up what we find...
 

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Any updates? Im having the same issue. I do mostly 1/8th mile which I have no wobble at all, straight as an arrow. Raced 1/4 this weekend lifted after the finish and the rear was wobbling side to side, felt very uncomfortable. Talked to three other guys at the track they all said oh ya that's normal mine does that too, it's the track. I don't particularly like that answer. Checked my suspension , everything seems to measure perfect side to side, shocks set even side to side, bump steer was mentioned but I do not feel it in the front end/steering wheel, alignment seems good, wobble feels all in the back to me. I'm puzzled, I'm searching for possibilities..

Car is a 69 Camaro, four link, stock front suspension with aftermarket rack and pinion, 3000 lbs, traps 136-138mph
 

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Front end felt in steering or body roll side to side?
 

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If it has an anti-roll bar in it make sure it doesn't have any preload. I put 1/2 a flat of preload in my upper bar during time trials one time and didn't re neutral the anti-roll due to time constraints. It felt like it was going to swap ends on me as soon as I got out of it at the stripe.
 

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"Shocks don't matter"
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Any updates? Im having the same issue. I do mostly 1/8th mile which I have no wobble at all, straight as an arrow. Raced 1/4 this weekend lifted after the finish and the rear was wobbling side to side, felt very uncomfortable. Talked to three other guys at the track they all said oh ya that's normal mine does that too, it's the track. I don't particularly like that answer. Checked my suspension , everything seems to measure perfect side to side, shocks set even side to side, bump steer was mentioned but I do not feel it in the front end/steering wheel, alignment seems good, wobble feels all in the back to me. I'm puzzled, I'm searching for possibilities..

Car is a 69 Camaro, four link, stock front suspension with aftermarket rack and pinion, 3000 lbs, traps 136-138mph
This might be helpful, think of it like this ... wrap up on 4 link bars on acceleration, wrap down on deceleration . Depending on wheel speed on deceleration vs torque converter & gear on deceleration it could be like hitting the rear brakes just lifting of the gas pedal. The real fast cars drive into the chute for this reason. I can't give you the exact answer because I don't know enough details BUT it most likely revolves around the aforementioned. Could be just a bad heim though as well.
 

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I would check all control arm mounting points to make sure a bushing hasn't worn out, bolt bent, or something just got loose.

I had stock type rubber bushings in my rear at one point and would get a weird wobble/shake at the top end of the track under power and off the power. Turned out the rubber bushings weren't good at those speeds, too much flex in them. Switched to solid bushings and no more issues.
 

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This is simply the body swaying over the rear end - the chassis is tracking straight - but the heims at the bars allow the body some side to side movement. A panhard bar will solve this condition.
 
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