05zexstang

I installed adjustable Ca's about a month ago, and I noticed that when I get to about 85 mph my rear end starts vibrating pretty bad. A couple of my buddies told me to get my pinion angle adjsuted and that would fix the problem. I was wondering if any of you guys have experience the same thing in your car.

Sleeper05

wow im not quite sure if i posted that or you...that is word for word my situation. im dropped 2in, how bout you? i get massive violent vibration above 80mph whenever i let off the gas...but never anything when im into the throttle or its engine braking, just for a couple seconds after i let off the gas. it scares me sometimes arg.

QuickShortBus

I've got adjustable upper and lower control arms on my car, I don't have any vibration but if you didn't set them to stock length then that is probably your problem.

If you are lowered significantly then that would also cause the pinion angle to change enough to have what you have happening, you will need to adjust the pinion angle in that case with the adjustable control arms.

FREAKO

I started getting the same vibration ...from about 85+mph..worse on decelerating when my ring and pinion was changed to 4.10. I had stock control arms, stock springs, stock driveshaft at the time.....I added the axle dampner kit...didnt really help.....looking to maybe use an axle dampner off a fox-body car if it will clear the exhaust.

dkano

How exactly do you adjust the pinion angle? Do I have to take the car to the dealer for that or can I do it at home? This is the same problem I have since I got the Steeda billet lower control arms installed, they's not the adjustable type.

FREAKO

pinion angle is the relationship of the pinion to the driveshaft (in degrees..which anywhere from 0 to 2 degrees in optimal or so I have been told)....the only way to correct it would be to add adjustable control arms and use an angle protractor

CrazyAl

Freako, did you lower your car?

The only way your pinion angle would change would be if you lowered your car, or if you purposely adjusted your suspension. You might be having a vibration problem, but chances are that it's not pinion angle related if you haven't changed your pinion angle.


If you want to adjust the pinion angle, you need adjustable control arms. You can either have an adjustable upper, or adjustable lowers. (Or both, but what's the point). Personally, I think the better option is adjustable lowers. They're easier to get to for adjustments. Plus, an adjustable CA is going to be weaker than a non-adjustable one of similar construction. So, better to divide up that potential weakness among two arms rather than one--the LCA's see less strain than the upper, since there's two of them to share the burden.


05Zexstang, if you got adjustable control arms, how did you set them? I'm hoping you didn't just bolt them in like they were out of the box. An adjustable part is only good if you know how to adjust it and you bother to set it correctly. Get under your car with a magnetic protractor and set your pinion angle. It should be easy as you already have the adjustable CAs.

FREAKO

nope..my car has stock springs..stock height....but now that i think of it....when i did the gear change, i replaced the upper control arm (non-adjustable).....and thats when the vibration started. If I get a chance, Ill replace that control arm with the stock unit and see how the car feels.

MusiccityGT

I put in race LCA's set to stock length, race Panhard bar at stock length (I'm not lowered) ,torque box braces and an adjustable Steeda third link. When I set the pinion angle, I borrowed a digital inclinometer from a ford dealer tech. The setting should be between 2% and 5% negative. I set mine at 3.8% and have no vibration at all. I would definately say that your pinion angle is off.