Driveline vibration

[Royce]

My 61 Starliner has a resonating drive line vibration . The frequency leads me to the drive train... So far I have replace U joints,balanced the drive shaft,  inspected the axle bearings, and even changed out the gears.. No change... The vibration is rpm related and is worse under power and less if you let off the gas..I am 95% sure it is not coming from the engine compartment..  I would have put my money on the drive shaft but the shop said it was perfect.

Any ideas

RB

[shady]

Tranny output shaft bushing or bearing? Torque converter?

[jayb]

Which engine and trans?

[machoneman]

Has a clutch fan gone south?

Have you considered running the engine and drivetrain on a very well blocked up car? 

[C6AE]

"Hunting" gear set in the differential?

[gt350hr]

   Royce ,
      Look at your pinion angle. It could be pointing up too much and under power it rises even more creating a vibration. You may have already done that . It happened to me is why I relate it. Same MO , balanced , checked for straightness , new U joints etc. Bad angle.
    Randy

[chilly460]

Following as I have same issue, not terrible but I’ve fixed all the other nagging items so will look into this over the winter.  Mine has a specific speed it occurs and it rolls in/out

[Royce]

Randy  Pinion angle passes the eyeball test but I will put a angle finder on it..

 Jay, I so want to say a 292 and a 3 speed... But it is a 390 and a C6  Trans output bushing is tight.. Pray it is not the torque converter.. It was replaced about 1000 miles ago with a higher stall unit.. Does not have a clutch fan.. Getting a the vibration to come and go by getting on and off the gas keeps me thinking somewhere between output on trans and rear gears

[jayb]

Royce, is this a new development or has the car always had this since you've owned it?  If its new, what changed around the time that it started vibrating?  I think it would be worth looking at the torque converter and flywheel.  Maybe somebody stuck a 428 flywheel on the 390, or a balance weight fell off the converter, loose converter bolts, loose flywheel bolts, or something in that area...

[Royce]

I barely drove the car when I bought it before pulling the motor for a detail job and a makeover to 390 375 horse dress.. I don't recall if vibration was present.. Since then it has a new converter but original flex plate. I put it all back together. (Definitely a possible source of error)  I'll check the converter bolts and see if I can see anything on the flex plate or converter..

Maybe Brad Ford  knows of some gizmo that can isolate sources of vibration

[thatdarncat]

...Maybe Brad Ford  knows of some gizmo that can isolate sources of vibration

BradFord is actually very good at diagnosing driveline vibrations, he’s helped me a couple times. Sadly no gizmo involved, you need the actual BradFord. A phone call to him might get some suggestions though. I haven’t been able to get him to check the forum on a daily basis yet.

[badcatt]

Does it do it in Neutral or Park? I'm chasing a vibration in a fresh 351C. I too thought it was drive line. But after R&Ring U-joints it still did it. I then checked in Park and it was there. Currently I do not have a diagnoses.

[66FAIRLANE]

Had a vibe many years ago I couldn't find. Very subtle & only at higher speeds. One day a mate was driving behind me and when we stopped he said "I think your left axle is bent". I put a clock on the wheel rim & sure enough there was wobble, wasn't much, but was enough. Changed the axle, vibration gone. Just something else to check if its only there on road.

[cattleFEeder]

Just had the same problem on my 63.5 galaxie ended up being a wobble from an aftermarket rim that wasn't welded strait at the factory.

[e philpott]

Sounds like pinion angle to me too