I have had a vibration in my car since buying it. It vibrates really bad at around 65mph. I have had the wheels balanced 3 times. I took the car to tire discounters and they told me the front rim was bent. I took the car straight back to the dealership who said the wheel wasnt bent. I have done a test on the drive shaft by getting the vibration and changing down a gear and coming back up to 65 and it still vibrates. I check the rpms at 65 and brought the car back up to that rpm in a different gear. Everything I do shows the vibration at 65mph regardless of rpm, which tells me it's not the driveshaft. What symptoms would the bent rim give you?

 

Why does this tell you it's not the driveshaft?

The driveshaft spins at the same RPM at 65mph regardless of engine rpm. I would have the shaft inspected.

My truck has the same problem and it ended up eating the crap out of the pinion bearing becasue the drive shaft vibrated so badly at 55mph for so long while I spent hours trying to figure out what was wrong.

Check the driveshaft!!!

 

It tells me it's not the driveshaft because when you change down a gear and you bring the car back to the same speed the driveshaft is spinning at a different rpm. This is the way you test to see if it is a driveshaft or not. Taken from the camaro workshop manual.

 

Well for what its worth when I had my vibration it would do it about 70 and it would happen if I was in third or fourth and it was the driveshaft.

 

The driveshaft spins relative to the wheels. Regardless of what gear/engine speed, the driveshaft spins at the same speed as the output shaft of the transmission and at the same speed as the wheels, less their gear ratio. So if you have 3.42 gears, the driveshaft will always spin 3.42 times for every 1 rotation of the wheels, regardless of transmission gear. At 65mph your 26" tires/wheels are spinning at 14.01 spins per second, and if you have 3.42 gears, your driveshaft is spinning at 47.9 times per second. That is independent of engine speed or transmission gear. If it is in fact your driveshaft, you should hear/feel the vibration at 65mph at aproximately 48hZ.

The engine speed may vary but if the vehicle speed is the constant it tells me it's something AFTER the transmission. 65 mph in 2nd, 3rd or 4th gear has the same driveshaft rotational speed as the previous gear.

I had the same problem in my truck - it did it at the same speed, regardless of engine speed or trans gear, and it turned out to be the driveshaft out of balance & a bad pinion bearing, allowing the pinion yoke end of the driveshaft to move up & down 1/4" each direction

Good luck!

-Mike

 

Taken from the haynes repair manual, Quote "" 55 VIBRATION " Install a tachometer inside the vehicle to monitor engine speed as the vehicle is driven. Drive the vehicle and note the engine speed at which the vibration (roughness) is most pronounced. Now shift the transmission to a different gear and bring the engine speed to the same point.
If the vibration occurs at the same engine speed (rpm) regardless of which gear the transmission is in, the drive shaft is NOT at fault since the driveshaft speed varies.
Anyway, what sort of price you looking at to get the driveshaft balanced?
Paul

 

That's talking about engine speed - aka RPM, not vehicle speed.

Most shops I've talked to want $45-60. I've gotta do that to my truck before winter still yet.

Let us know what it ends up being.

-Mike

 

He's right the repair manual is talking about engine speed and the camaro's (including mine) had a driveshaft problem. You must check your driveshaft if you are certain it is not your tires. Please don't take offense but it definately sounds like you are misinterpreting what the manual is saying here.

Chase