Vibration in Camaro

[David Tx]

Hey people,
I have a 69 Pro touring Camaro that I bought off of ebay and I know yes I got stung
I have had the entire drivetrain out of car looking for Vibration and figured I found it when it had a 350 flywheel instead of a 400 fly wheel
went through drivetrain cause the workman ship was like the car was built by monkeys.
well got it back together and it vibrates the most at 2000 rpms in 4th gear but at 2000 rpms in fifth gear its smooth as silk.
Im no novice mechanic 35 years doing it for a living but this is driving me crazy and any ideas anyone may have will be greatly appreciated.
the car was a mess when I got it I have been through the rear end rear suspension had the engine half way apart to make sure the wrong flywheel didn't damage the bearings and this is my 14th first gen camaro so I know them pretty well.Im wondering if I should have kept my prostreet 69 it was flawless but you couldn't travel much over 75 miles one way in it with the price of gas lol.
please help if you can with Ideas.
Thanks David @ Corvettes and Customs
opps i forgot 406 engine Viper 6 speed mini tubs ford 9 inch rear sub frame connectors Competition engineering slider bars 4 corner Willwood disk tubular front control arms with coil overs

[BonzoHansen]

edit: reading failure at night, lol.

"well got it back together and it vibrates the most at 2000 rpms in 4th gear but at 2000 rpms in fifth gear its smooth as silk."

[Tom Welch]

driveshaft? flywheel not balanced?

[Vegas69]

It can't be engine related because it's not present in both gears. It's doubtful it's driveline angles because it gets better at a higher speed. I'd be looking at the driveshaft.

[MrQuick]

It can't be engine related because it's not present in both gears. It's doubtful it's driveline angles because it gets better at a higher speed. I'd be looking at the driveshaft.
That would be true with the balance. Also check your universal joints....and engine/trans mounting? Are they solid?

[TT302Z28]

I've had this same problem in the last 2 cars I bought. One had a driveline that was too short and another out of balance since the mufflers were allowed to get too close and knock off the balance weight.

[JEFFTATE]

Sounds like the driveline angles That's very common with lowered vehicles.
( or the driveshaft balance.)

[Jim Nilsen]

It seems that the driveshaft is out of balance and then at a higher speed of rotation it smooths out . It is common to have it cycle.

You are running a higher driveshaft speed in 5th, if you slow down in 5th ,how much does the vibration come back? This little test will help isolate it if you go by the drive shaft speed for observation.

[GRNOVA]

Make sure if your running a balancer with a weight on it that it is not on the same side as the weight on the flywheel. This can cause the same kind of vibration you are talking about.

[nc69rs]

I was thinking about your flywheel, what if the motor was internally balanced? You would have a 350 balancer on the front and a 350 flywheel with no weights. I used to run a 408 that was internally balanced, that's why I thought of it.

[tonykim]

driveshaft is my vote. I've even had them rebalanced in an attempt to get rid of just such a vibration.

[killer67]

Driveline angles or U-joints