My 65 has a serious shake throughout the entire car (fenders, windows...everything) at about 53 MPH. It's developed over the last 9 months. Today I took the driveshaft out and had someone pull me with my engine off and it still shakes. I assume this eliminates engine, trans and driveshaft. Since this started I have replaced the tires (balanced 3 times), rims, front suspension, all wheel bearings, had the differential rebuilt, axles checked. Assuming something hasn't been missed (axles aren't straight etc), there's not much left that actually spins. The only thing left that I can think of are the brake drums and EVERYONE is telling me that it can't be them. They don't pulsate when braking, but to me there's still potential they aren't balanced. The back drums have weights, but the front drums don't.

I've had both rear tires in the air with the speed up between 45 and 60 and get minimal vibration. Nowhere near what I get on the road. Did the same with one tire down and the other spinning with the same result. Even did it without the drum and got the same. Tested both sides.

So, I'm here hoping that someone can give me an idea as to how to further attempt to diagnose this, or give me a clue about something I've missed. Maybe something's loose as opposed to out of balance? I really don't know at this point.

Any help is appreciated.  

Check the front brake drums.  The wheel studs are mounted on them and a front wheel could be wobbling because the hub in the drum has gotten whacked.  Also, have the rear axle bearings at the end of the axle housing been checked?  Check the leaf spring mounting at the front and the shackles at the rear.  If the rubber in the leaf spring mounts has failed, it could allow the rear axle to move around.  Good luck because you have done a lot already.  

If it only happens at that speed and not before or after, then most likely it is a wheel balance problem.  Try to find a wheel balancer guy who has one of those balancers that checks the balance while the wheel is still on the car.  It used to be called "speed" balancing.  That way, it will take into account your wheel, tire and brake drum.  If you only check the wheel and tire for balance, then you are not balancing the "whole" wheel area.  If the problem was wheel bearings, or U-Joints or any of the other drive train items, it would shake at more speeds than the one you indicated
But, just for grins, and this won't take but a few minutes, try jacking up your engine and see if both motor mounts are still connected and not one or both broken.  

soaring3 - Thanks for the info on the balancer. I've checked a couple of places about the "on the car" balancing and have a few more leads. Checking them that way would really allow the issue to be isolated to the exact wheel. I'll check the motor mounts just for fun.

pkbkfcw - Your hub comment triggered something. When I checked the front left bearing race I noticed some unusual wear and attributed that to the local tire guys greasing the bearings and not properly tightening things up (wheels on both sides were loose). After replacing the race the shaking continued so I eliminated that issue. However, maybe a whacked hub is causing the unusual wear and is now wearing the new race...Hmmm...I'll take the drum back off and look it over. If the unusual wear is back you may be on to something. I'm also wondering if the race is seated properly.

Now to your leaf spring comment. I replaced the shackles and the front bushings so I think those are tight, but could weak springs cause anything (other than the rear of the car sagging and poor handling)? After the new shackles were put on, the mechanic told me the new ones were 3/4 inch shorter than the original. <sigh> I called the supplier and he assured me the new ones were correct (not sure about that one). After checking I found the rear to be 1 1/4 inch lower than the front...so leaf springs are on the list.

And finally...Yes about the axle bearings. I had them replaced when the axles were checked.

Sorry for the long-winded post.  

Jack the car up and spin the tires individually to see if the tire shop bent any rims when they put on new tires (it happens-i've done it and seen it)otherwise its in the tire balance.  

More information.... I checked the front hubs and one looked odd so I replaced it. I also replaced the rear suspension (since the back of the car was sagging anyway). While doing this I noticed two things. The left rear frame rail that the shackle attaches to was rusted out so that's getting replaced today (I'm hoping this might do it, since I can't image the axle is completely stable with little support at the rear left leaf spring....) When I put the leaf spring into place and lowered the axle housing to meet it, I noticed alot of play where the "nub" on the leaf spring didn't fit snuggly into its counterpart on the axle housing (not even close). I could move the axle housing about 3/4 inch back and forth before tightening things down. So maybe I'll take it to an alignment shop and have them check to insure the rear axle is aligned properly. The saga continues....  

Yeah, if that shackle mount is rusted out, then don't even attempt to drive it until a new chunk of iron is welded in there to replace the cancer and the rear shackle mount is stabilized.  I can imagine seeing that car going down the road and the rear end is swinging back and forth more than a woman breaking in a new set of high heels.  

Check your tires too.  I had a similar problem, car only shook on the freeway.  At one point, I noticed the tires seem low (but not that low).  Brought them up to pressure and went out on a drive.  Problem was better but not gone.  Then, going around a bend in the road, at about 40mph, and POW, I blow the front driver's side tire, the tread basically peeled off all the way around the tire.  The tires had been on the car for some time.  Tread was fine, but on inspection, found small cracks in the sidewalls.  5 new tires and it rides nice.

Jeff  

Well...after fixing the leaf spring/axle perch issue as well as the rear frame rail...it still shakes. Had the rear axle housing alignment checked to make sure it was running down the road straight. All looked good. I'm going to replace the left hub just for kicks and probably the front drums since I've learned that they are cheap (stamped) after-markets.

Thanks for the comment Jeff. These tires are new and the shaking existed with the original tires prior. However, these could be bad too. You never know. I found a local car dealer who has a machine that can true up a tire that may be slightly out of round. I may try that too.  

I also found one other thing that seems odd. On both spindles, at the back round plate which the inner bearing presses against (and the dust cover goes around), there is a thin groove about 1/8 inch wide and deep enough to catch a thumbnail on. It seems to match the diameter of the inner bearing casing (although I have to confirm that). I'm trying to figure out if this is normal and maybe came from the factory this way, or if this is abnormal wear. It almost seems too consistent to be abnormal wear and weird that it would have done it on both sides. I found a picture on MustangMonthly that showed the same thing on a spindle, but since the article was not about spindles it's hard to know if the spindle was good or bad. Anyone else seen this or know anything about it?  

I have seen wear marks on the inner spindle in the area of the large machined surface due to the seal rotation and as long as it's not too deep and a new wheel seal doesn't leak, it's ok to use.  If you are seeing wear on the spindle in the area that the inner bearing rides, (the area immediately outboard of the seal) that's not a good thing and may possibly lead to catistrophic bearing failures due to whatever factor is causing the groove.  

Just want to make sure we're talking about the same area. I'm not talking about the area that the bearings and hub slide over, but the back part of the spindle that the inner bearing would butt up against. The dust cover goes around this part. The wear caused by the seal would show on the outer edge of this area. I'm talking about the flat surface facing the back of the inner bearing. Are we talking about the same spot?  

It sounds as if you have narrowed it down to the shaking is happening from a default in the front suspension.  Is that the case?  

Take a good look at the idler arm. A worn idler arm can cause a wicked shimmy however it's usually at a lower speed.

Good luck  

sbwils:
Just want to make sure we're talking about the same area. I'm not talking about the area that the bearings and hub slide over, but the back part of the spindle that the inner bearing would butt up against. The dust cover goes around this part. The wear caused by the seal would show on the outer edge of this area. I'm talking about the flat surface facing the back of the inner bearing. Are we talking about the same spot?

Yeah, i understand. It's not really normal to see machining there cause the inner bearing is supposed to be limited in it's axial range based on the diameter of the spindle to the diameter of the bearing's inner race.  It's possible that your bearing's inner race is not correctly sized(cheap option-replace the bearing and race) or the spindle is undersized (not so cheap option). I would assume that the other side does not have this same marking.