[Steve Shively]

My 1971 Lemans has always had a vibration issue, kinda seems worse. Thinking driveshaft was not correct, I pulled it & measured, 551/2 " thereabouts. Seems tight in car, not much end play. Other suspicion is torque converter bad. Any ideas? I know it is hard to diagnose on the internet!

[Sirrotica]

Drive the car to the speed it vibrates at , kick the transmission into neutral and shut the engine off being careful not to lock the steering column. If the vibration is still there during coast down it's in the drivetrain, not the transmission or engine. Revving the engine in neutral with the car sitting still will isolate the engine/torque converter vibrations.

Very likely a bent driveshaft or one of the welded on weights flew off the driveshaft. putting the car up on jackstands and running the rear wheels will differentiate whether it's in the front or rear axle. While it's in gear you can also look at the driveshaft to see if it's running true.

Other sources are a bent wheel, shifted belt in a radial tire, usually more noticeable at reduced speeds you can feel the thumping just barely moving.

These are the common areas to look for vibrations in most cars.

[Steve Shively]

I will look into ASAP,

[Steve Shively]

Looked at the driveshaft, as it is out of the car. There are two weights tacked on at both ends of the driveshaft. There is no weight on opposite side of each weight..

[Sirrotica]

The only way to tell absolutely if the weights have fallen off is to have a driveshaft shop balance it and check that it hasn't been bent.

Binding U joints, worn needle bearings cannot be discerned by just a visual inspection.

[Eric71T37]

I had my driveshaft balanced and it got rid of a nasty vibration at highway speeds.

[pggto]

Do you feel the vibration in the car or do you feel it in the steering wheel? The easiest thing to check for first is a loose wheel or wheel balancing weight. A radial tire may have a belt separation, inspect the tires for any bulges. As mention above have the driveshaft checked. I think it cost me about $125 to have new u joints installed and the shaft balance at a driveshaft shop a few years ago. Inspect the suspension bushings to see if the rubber has dry rotted away causing the rear end to possibly be out of line. Same thing with the trans mount.

[Steve Shively]

A lot to look at, lol! Been raining for 14 days & more coming, ugh...

[Scott Thelander]

rain in Kansas city ?

https://www.wunderground.com/cgi-bin...kansas+city+ks

looks like youlle have lots of dry time comin up............... to get 'er dun ........

Must be two 2 diff Kansas's .............

[Steve Shively]

Kansas City

[2002Z4CSS]

Put the back of the car up on jack stands and run it in gear. If it shakes the vibration is in the driveline. Get a spirometer from a local small engine repair company and measure the frequency of the vibration and the RPM the engine is running and speed you are going, That can be calculated to what order the vibration is. 1st, 2nd, 3rd.