Technical Vibration at 85, 1962 Mercury

I have a vibration that Ive not yet figured out on my 1962 Mercury Monterey. It becomes intrusive at 85mph but is noticeable at about 75mph. It’s speed not rpm related and it’s driveline not front end, as if I run it on axle stands it’s still exactly the same as on the road. Here is the bit I can’t get my head around. Run it without wheels and brake drums it it still there, put the wheels back on and it is worse, put a different set of wheels on and it is just the same as the other wheels, both sets of wheels have been balanced twice.

The thing I can’t get is why putting the wheels back on changes the amplitude of the vibration but the frequency and point it happens is the same.

UJs are new, no nasty noises or play in the driveline. There is a small amount of play in the wheel bearings but not outside tolerance. It’s a stock early 9 inch.

Any thoughts??

 

Drive shaft balance?
Dan

 

Thats one of the things I was thinking of but I can’t understand why putting the wheels back on makes it worse.

 

It might be rear axle run-out. To test put a bare wheel on a front hub to check the wheel for run-out, if the wheel tests good try it on the rear hubs. Also, if you use drum brakes one of the brake drums can be out of balance.

 

I’ll try that.
I did check the drums, on or off no change.

 

One easy thing to do is use a hose clamp on the drive shaft. You can clamp tight drive if vibration is worse or same move 1/4 turn and try again, repeat until the vib is gone.You also can clamp the hose clamp snug but not over tight, the theory is that the clamp will find the spot with lowest vib. I’ve never done the second method, the first method does indeed work sometimes requires more than one clamp.
Dan

 

Drive shaft or bent axle. Where are you allowed to go 85?

 

@Oneball is in England,
In Wisconsin have you ever driven in Mad city or Milwaukee anywhere on 94.
I live in the sticks where the owls do unspeakable things to the chickens.
I see the sheriff on my road maybe once/ year he he ha ha
Dan

 

I would pull the driveshaft and take it to a shop that specializes in driveshafts and u-joint replacement. Have them test it for balance. That will either be a cure or eliminate it as the cause.

 

I had a vibration at about 60 once, I fixed it by getting up to about 90 on the freeway to catch up with my buddy. the vibration was gone after the driveshaft flew out. saw it in my rear view mirror with a big bend in it about 10 feet in the air. cracked all 4 mounting ears on my 4 speed.

 

Just trying to keep the traffic flowing, officer

My dad actually used that line when I was a kid with him in the car, the copper let him off too

 

Officer..... Your eyes are red, have you been drinking? You to officer..... Your eyes are glazed, have you been eating doughnuts? And that's when the trouble started.

 

It gives the rotating pieces more m*** which increases the amplitude of the vibration.

 

You can refine this by using a piece of chalk to mark the heavy spot while the shaft is turning and vibrating. Back in the day I had access to a Stewart-Warner strobe wheel balancer. It worked quite well to determine the heavy spot on a drive shaft.

 

"Run it without wheels and brake drums it it still there, put the wheels back on and it is worse, put a different set of wheels on and it is just the same as the other wheels, both sets of wheels have been balanced twice."

maybe a bent axle ??? sounds like something in the rear end.... pinion bearing???

 

I had a similar problem in my old street/drag truck. Vibration developed at 55mph and increased with speed.. Pulled the 9" apart and I had slightly twisted (not bent) the driver-side axle shaft from too much "squirreling" around. Replaced the axle and bearings...vibration gone.

 

If you can drive through the vibration it’s the drive shaft. If it gets worse the faster you go it’s wheels, axles and hubs. Had a bent rear end housing in a 75 Oldsmobile Cutl***. Only way I found it was I finally got pissed off and just replaced the whole thing. After replacing axles, all bearings and posi carrier and gears. Expensive lesson learned the hard way.

 

Gets worse and worse to the point it’s so bad you have to slow down.

 

Thanks
Learn something everyday.
Dan

 

Start looking for a bent rear end housing. The one I had was only off 1/8”. That ****ed to finally figure out. It was a 10 bolt 8.5” Olds rear end.

 

What is the speed limit in England?

 

Speed limits?
Usually I’m limited by HP and aerodynamics lol
Dan

 

Depends on where the cops are?

 

One possibility may be a two piece driveshaft that some of the more expensive cars were getting
with RWD supposidly to keep vibrations down.
The inner shaft was in a rubber cushion from the outer shaft.
Found a few in later year donor cars. Easy to check by looking closely at the tube.

Detroit automakers began experimenting with and implementing rubber-inserted driveshafts and rubber driveshaft couplers in rear-wheel drive (RWD) applications as early as the 1960s, primarily to dampen vibration, reduce noise (NVH), and account for drivetrain flexibility.

 

30 in town, 60 on single carriageway, 70 on dual carriageway (central divider). Obviously I was on a closed road with a professional driver.

 

Measured the run out at the wheel rim and it appears to be in the range of 0.02-0.03 inch so I don’t think it’s a bent axle shaft. Will try the hose clamp on the driveshaft next.

 

All this speed limit talk in England reminds me of a cab ride I once had in London. Pretty sure we saw 140 mph between where he knew where the cameras were. I at first through it might be kph, but verified it was mph. Anyway, it was all caused by a mix-up of what airport we were flying out of. We stayed real close to the airport we thought we were flying out of. However, we were wrong... We did give him a HUGE tip for getting us to the other airport in time to catch the flight.

Back to the problem at hand, sure sounds like driveshaft especially since you have verified run out at the wheel.

 

I’ve put some hose clamps on the driveshaft and it makes no appreciable difference. The only thing Ive noticed is the right wheel bearing sounds grumbly but there’s no apparent play. I guess I can change the wheel bearings and see what happens

 

A wheel bearing can cause vibration, hopefully that’s it.
Dan

 

Although there doesn’t seem excessive play at the wheel, the bearing is appreciably knackered.

https://oneball.smugmug.com/Cars/Merc-Original/n-5ZtcCv/i-XF3XtsN