mgreen

Regardless of engine RPM or what gear I'm in (6spd), I have a vibration that begins at ~45mph and increases with speed from there.

I've swapped rear wheels, so I know the wheels aren't out of balance.

So now I'm down to the rear & DS.

The rear is a stock 10bolt w/ girdle & 4.10s. The 4.10s have no whine and are holding up well.

The DS is a stock Aluminum.

Any thoughts or ideas??

Thanks
Mike

kp

iTrader: (34)

I assume you feel it in the shifter but dont rule out the front tires if you havent swapped them..

It can be something in the trans or driveshaft/u-joints. You could also have a bent axle so matter what wheels you put on the back it will vibrate.

Easy enough to get the driveshaft checked for balance, sometimes the weights come off. Just going to have to start eliminating things one by one if it bothers you.

mgreen

Thanks Kevin (weren't you banned for a while!? )

Anyways, I feel it in the back half of the car and then the whole console begins to vibrate a little. . .but I really don't feel it in the shifter (although it's really hard to tell with hotcam, LT's, no cats, and a straight through muffler. . .and the poly trans mount since everything seems to vibrate a little.

I'll be putting it up on the lift tonight, so we'll see if any weights appear to be missing from the DS.

Would a bent axle make any other strange noises?? Also, if it's that bad, wouldn't a person be able to drive next to me and see the wheel moving in an abnormal fashion?

Mike

kp

iTrader: (34)

Wasnt banned, just a time out for typing when I should have been reading

you could just spin the wheel on the lift and see if its running out or not. One of my new moser axles runs out about .030 on the flange and moves 1/4 an inch at the wheel rim. I have so many vibrations between the converter, exhaust and rod ends on the t/a and LCAs I dont even notice it..

If you can put the car in neutral and shut off the car off and it still vibrates at those speeds then look at tires/axle driveshaft, u-joints/pinion angle. You can also put it on a lift and support the rear end and run it up to the speed it does it at. There are so many things, including the exhaust, that can pick up and amplify small vibrations from something else, it makes finding it pretty rough unless you have spare parts to swap around..

mgreen

yeah, I thought about that after I posted. . . I can just lift it a couple inches and drive it up to speed. . .

well, we'll see about it tonight

mgreen

ok. . . swapped DS's, and vibration is still evident.

removed wheels, vibration still evident. . .

looked at wheels, no movement.

Drove car on lift w/ no DS in place. . . vibration not there.

On the ride home, the vibration was nearly non-existent.

My Dad & I are thinking my Carquest (Made in China "upgraded" ) brake rotors, which we installed last week, may be out of balance. . .

So, final question(s). . . if the output shaft of the tranny was bent, would I still feel the vibration at the reported 50+mph even though the DS was not in place??

And, what are the chances of the brake rotor(s) being unbalanced??

Thanks in advance to you wonderfully knowledgable LS1Tech people!
(thanks kevin)
This place has just been a WEALTH of knowledge for me with these types of issues!

btw, I gotta get me some of them LS1tech shirts!

mgreen

ok, the problem is gone 100%.

I'm writing it off as unbalanced brake rotors.

kp

iTrader: (34)

glad you got it fixed, I could have sworn I posted a reply last night but i must have hit the wrong thing

Glad its fixed.