bad vibration

[speedyb-cc]

I left work the other night, short ramp fast accel, and when I got on the freeway developed a sudden vibration at about 65-70mph, not steady but on off at about 1 second intervals, almost a shudder.
Pulled the driveline no bad joints, tried high rpm in second and it's still there,so is it coming from the trans or motor? Mounts look good reved it up in gear, no lifting, could the rear mount be broken (replaced last year)? When going from dr to rev sounds like its in the tranny. Also been hearing what sounds like rocks, or pieces of metal hitting underneath at city speeds, could be the new front tires catching rocks, nothing obvious that I could see underneath.
Any help would be greatly appreciated.
Thanks and God Bless
Bruce

 

[RedFish]

I had a crack in the front pump driver, neck on the torque converter, that seemed like hammering the floor pan under my feet. Good luck

 

[adriver]

So by high rpm in second do you mean moving at the same speed of 65 to 70?
That may be a stupid question. But we are trying to rule out tire problems.
If the engine and transmission parts are changing speeds but the drive shaft, rear and tires are not that is what I am talking about.
Look at what doesn’t change.
Does coast or power make a difference?
I had a Challenger I gave up on.
Got rid of it anyway.
Had an annoying oscillation at high speed.
Drive shaft checked and double-checked.
489 all new bearings.
I think it was harmonics or tires.

 

[djwhog]

Get up to say 70-75 shut off the motor and put her in N. Is it completely gone? If so then can you try N with the motor running, is is better or worse?

May be a driveshaft even if joints are OK, a front trans pump or output shaft bearing, engine balancer or maybe worse thrust main or other.

Kinda sounds like a tranny issue, i would pull the pan if everything else checks out OK from inspection pont of view. Sometimes once the pan is off you will see an issue if it is real bad.

 

[speedyb-cc]

Thanks for the input all, I'll try more tests tomorrow, it's always had a slight high speed vibration but this just started the other day.
Thanks again
Bruce

 

[Longgone]

I left work the other night, short ramp fast accel, and when I got on the freeway developed a sudden vibration at about 65-70mph, not steady but on off at about 1 second intervals, almost a shudder.
Pulled the driveline no bad joints, tried high rpm in second and it's still there,so is it coming from the trans or motor? Mounts look good reved it up in gear, no lifting, could the rear mount be broken (replaced last year)? When going from dr to rev sounds like its in the tranny. Also been hearing what sounds like rocks, or pieces of metal hitting underneath at city speeds, could be the new front tires catching rocks, nothing obvious that I could see underneath.
Any help would be greatly appreciated.
Thanks and God Bless
Bruce

Bruce , did you ever figure this one out? I`ve got what sounds like rocks flying up or popcorn popping under my feet accompanied by a whirring type of vibration. Seems to be under acceleration and disappears when coasting. Sort of sounded like what you experienced and I was curious as to what you found.