kevin_pianoman

Hey guys. I just had lowering springs put on my 98 Mustang GT today. It looks awesome but when I started driving it now it's making a nasty noise under hard acceleration. What I the world has happened now? Driving normal it makes no noises but under WOT it makes a very odd noise in the drive line. Not the engine. Please help.

DillonInCO

Need some more info...firstly, what kind of springs did you put on, and did you do shocks or or other suspension mods too? Second, what kind of noise is it (like a whining or a clunk)? Does it do it constantly under WOT or just when you get on it? And what part of the car do you think it's coming from (front, back, center, etc.)?

ModBargains

Have you brought it back to the place who installed it? If you installed it yourself, I think it's time to bring it to a local shop to get looked at, sounds worrying if you ask me, hopefully it isn't too bad.

I'm thinking the pinion angle isn't set up right, often times on lifted trucks you can get the same reaction if you lift a car up in the air too much the pinion angle isn't set right, so at WOT it can cause noises, that might be it, but get it checked out.

kevin_pianoman

The springs were bought from American muscle. They are designed for my car. The total drop was around 1.5 inches front and rear. I replaced my stock rear shocks and put new quad shocks on the rear as well. They are heavy duty KYBs. Front struts I left for now because they were fine. When I bought the car 4 months ago I had the rear end rebuilt so I know it's not that. It only seems to do it from a dead stop going through 1st and 2nd under hard acceleration, or when I hit a hard bump. The sound is like a chattery grind. Almost like if metal was dragging on the ground but it's not. There is plenty of clearance. A couple friends of mine say its the universal joints making that noise. Could they do that under hard acceleration or when driving and hitting a hard bump? I jacked the rear of the car up and moved the wheel back and forth with the car in neutral and it's making a clicking/slight clunk. Any thoughts before I take it to the shop today? Just seems weird that this noise wasn't there until I dropped the car. My friend said by the looks of it the joint had been bad for a while. Help.

kevin_pianoman

Also why would dropping the entire body down 1.5 inches change anything on the drive line? The car isn't sitting any different just lower. The drive shaft shouldn't have changed any, right?

LilRoush

Drive shaft rubbing exhaust now? It will have changed angles.

kevin_pianoman

I had it on the lift today. Nothing anywhere is touching or hitting. When you give it hard acceleration and the rear sets down there is a grinding noise around where the drive shaft goes into the transmission. Why? Only when you accelerate hard and the rear sits down or when a bump is hit. What do I need to change? control arms? If the control arm bushings are weak could it be causing the rear to twist and make the transmission and drive shaft not line up right and grind? Help please.

DillonInCO

Could be U joint, those generally tend to cause clunking or vibration though, not necessarily grinding noise. But I wouldn't rule it out. The click / clunk could also be wheel bearings.

The axle is bolted to the body, right? When you lower it, the axle is sitting closer to the body. Changing the height of the diff relative to the body changes the pinion angle. I could be wrong about that, but it makes sense to me---you can even watch the pinion angle change as you raise the car on a lift. However, a 1.5" drop shouldn't be enough to make the pinion angle so out of whack that it would cause something like this.

Did you put a load on the rear wheels / diff to simulate what it would be like if it were on the ground? Keep in mind that the way the suspension behaves off the ground is completely different than how it behaves on the road.

Last but not least, if you could post exactly which shocks and springs you went with, that'd be helpful. Unless the KYBs you bought are the AGX model, I think it's entirely possible that they're not stiff enough to handle the lowering springs.

antwaan

Yeah what exact parts did you get? I got the Ford "B" springs on my 96 with KYB gas adjust shocks/struts/quads with MM C/C plates a year ago and am extremely pleased with them. I get some creaks in the rear but that could just be not enough grease or my worn out control arms that I'm planning on replacing soon.

hawks05

Did you purchase isolators with your springs?