weird vibration

[70challengerrt]

The Roadrunner I restored for a guy is sold. The old owner is waiting for shipping. He drove it home and it was fine. He took it out for a run the other day and said it has a vibration in it. The driveshaft was balanced, rearend rebuilt so it not those. He said he thought it felt live the torque converter. I thought from his discrition it sounded like an exhaust rub. Is there different torque converters for steel and cast cranks? He has a cast crank in a 72 440 (I know it wasn't the right crank). The thing it just picked up the vibration. The motor, 727 tranny, rearend were all rebuild and have less than 50 miles on. I need some suggestions on what to look at.
Thanks
Todd

[Chryco Psycho]

440 cast cranks need a balanced converter

[tactransman]

The torque converter should have weights like this one:
Cast crank 440

[MEK-Dangerfield]

This isn't the optimum test, but let him put it in drive, and nail the gas with his foot firmly planted on the brake pad. If he feels any vibration before the car starts to move, it's the torque converter.


  Mike

[ntstlgl1970]

It would be pretty weird for the torque converter to suddenly start vibrating unless it threw one of the weights off or one of the spot welds on weight broke and caused to weight to move. And if it lost a weight, the weight would still be contained in the trans bellhousing I bet (unless the cover wasn't reinstalled). You need more info from this guy. When does it vibrate? will it vibrate out of gear? Will it do it in reverse? If it vibrates when you take off, does the vibration change? I'm kinda suspicious of anyone that can immediately identify a torque converter as a source of a vibration. Unless it's someone like tactransman or chryco.

[tactransman]

I assumed that the vibration might have always been there ,he just started to notice that it was there. If it doesn't vibrate when you rev it up in park ,it isn't the torque converter.

[70challengerrt]

I called him this morning and told him to run it in first gear to the same rpm that he gets the vibration in drive. That way you can narrow down the search. I found out that he got the car back home and when he went for the ride he beat it pretty good (couple of hard accelerations and a power stand) and considering the motor and tranny have less than 50 miles may be something loosened up. I personally thought it was a bad decision on his part to run the car hard or at all considering it is sold and waiting pick up but its not my car or decision.

[moper]

Sounds more to me like a skip...maybe he melted a wire or fouled a plug... I agree. Once sold, leave it parked. I have a friend who bent a pushrod beating on his sold car. So he had to scramble to get it repaired before the transporter showed.

[ntstlgl1970]

 

things like ignition issues or maybe a broken motor mount would be more likely

[ShelbyDogg]

I run mine hard sometimes too.  What I found is that the tires rotate on the wheels.  I mark my tires to my valve stems and know right away that the tires moved.  I had to stop at a Walmart halfway through the 2006 Power tour to have a quick rebalance, to fix a vibration between 85 and 95 mph.  It fixed it.   I'll have to drill and screw my wheels to stop the rotation. I even tried to glue the bead to the wheels, but they still move.

Did he say it vibrates while moving or in idle revving?

[70challengerrt]

Only when driving. Its like a pulsing drone he said. I a going to take it for a ride this weekend to get a first hand experiance.

[tactransman]

Make sure the u-joint caps are tight in the rear end yoke and that they have the clips on them to center it in the yoke ears.

[ShelbyDogg]

If you have another car that is smooth to 100 mph, throw the wheels and tires on your car for a quick test. If it's the driveshaft, it would vibrate on jack stands with the rear wheels off.