Hot Rods '32 Roadster Shake/vibration at 60-65 mph out of the blue

First off, this car has 39,000 miles and is driven lots. 32 Ford Roadster, tube front axle with 4 link, 9" ford rear with coilovers. No vibrations or issues at all previously, at any speed.

About 2 weeks ago I noticed a slight vibration on the highway at about 60-65 mph. When I got to the cruise in I was headed to, someone noted that one of my tailpipes was hanging down, and that I had a broken rubber hanger. "Great" I thought, that dangling pipe explains the vibration I was feeling... Except I got it fixed the following day and the vibration as still there. I then drove it to Columbus this past weekend, and put about 500 miles on it. The vibration was not constant, but seemed to happen around 60mph, and seemed more noticeable under load. Even when put into neutral you could feel it slightly. hard to determine where it was coming from, almost felt like the whole car was shaking.

When I got home I checked the universals, both were good, with no noticeable play. Pinion has a bit of slop, but likely always has. Tires were firestone repop bias ply, and I just so happened to have a brand new set ordered, so I had them put on, hoping maybe that would help... it didn't, in fact it seems worse now if anything, but the shake is still at the 60mph area and higher. Below that the car seems to drive nice, like it always has.

I do have some play in my kingpins, but could this cause the whole car to shake at 65 mph and still drive fine below that? No changes to pinion angles or anything like that, and as I said, the car drove perfect prior to last week. I even took a pair of rear wheels/tires off something else and tried them, and the same vibration comes on at the same speed. I'm at my wits end trying to figure out what it could be... any ideas?

 

Wheel bearing?

 

Don't think so... no noises or anything, and it's perfect under 60 mph.

 

Can worn kingpin(s) cause a vibration or shake that doesn't appear until highway speeds? I have no "death wobble" or anything like that over RR tracks, bumps, etc... at any speed.

 

Put he car up on jackstands, start the engine, pull the transmission into low gear. Get out and look at what the tread and sidewalls of the rear tires are doing.
If you can see anything that doesn't look smooth as butter, or square with the world, you will be observing what needs to be corrected. If you hear a noise that doesn't match how you think it should be. then it could be a bearing or axle problem.
My bet is tires. Reason being, I've test driven many vehicles for customers, and watched dozens more with separating tires. If that is the case, separating can cause many odd sensations, to include shaking a vehicle to death, exhaust hanger being the early sign. Some of my co-workers performed old style front end alignments, and wheel on vehicle tire balance. I worked some of the service desk functions during the last 5 later years, car and big truck.

 

You got mud in yer tires....

Do you notice it in the steering wheel or in the seat of your pants? You pretty much eliminated motor/trans when you still had it in neutral. Tires would vibrate around that speed... But you changed tires and tried a couple of different wheels. Did you try those on the front or rear? If it was a king pin or in the steering linkage you should feel it more in the steering wheel.

All a matter of the process of elimination.

You got mud in yer tires.

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Stand off to the side of the tread, and spin the rears at that 65 mph on stands. Rocks sling off if there. Bet you see a disformation.

 

Or, swap rear wheels with mounted tires to see if you make a change.
I save the radiator on my car because of diagnosing separating front tires that looked new, I I knew when I had purchased them.

 

Go read his first post.... He changed tires.

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You never expressed the frequency of the vibration. If it's the drive shaft transmission engine Etc the vibration will be a multiple of your rear end ratio not if it's tires are bearings or alignment the frequency will be much lower so is it a high frequency or low frequency? So is it like a hum or a roar or a bump bump bump?

 

Car shaking in neutral at stopped or rolling?
And FWIW, of my 25 years of building, installing, diagnosing may kinds of driveshaft repairs, I've seen very few driveshaft induced vibration problems that shook enough at 20 mph to make you even have the desire to drive 60 mph. Shaft angle repairs and mods included.

 

I'll bet your keys rattle while your Coca Cola gets thrown out while going down the road.

 

Did that. even tired a known good pair of balanced wheels and tires off my buddy's Torino that drives as smooth as silk. Still had the same 60 mph shake. Balanaced and rebalanced all 4 of my own new tires and they're all as perfect as they're gonna get... and the real kicker is that this whole thing started with my OLD tires... so basically I've eliminated tires and wheels as a cause.

 

I notice it everywhere... in my gas pedal foot, the wheel, my ass, everywhere... yet its as smooth as silk up until 60 mph. Doesn't matter if you flog it to 60 or ease it to 60, as soon as you get there... the hippy shakes start.

 

My buddy who took it for a drive said it felt more like a "shake" than a vibration.. so I guess that would qualify as a bump bump bump. To me it feels like a shudder.

 

No, car idles smooth as silk. Drives smooth as silk to 60 mph....even if you flog it. No misses, no shaking, nothing.. til 60.

 

I actually had that problem30 years ago and it turned out to be front shocks.

 

Pinion slack isn't good for reasons not involved with this problem.
Could it be a twisted axle like one of my problems that I had to fix? Back to runout observations.
Speaking generally, as I have been, wheel speed is what most folks feel. I had to learn powertrain speeds for diagnosis and repairs.

 

Not the shocks... they're brand new So Cals and I actually drove it 40 miles home once without one of the front shocks on it at all and it didn't shake like this.

 

You mention that the pinion has some slop. It should not have any slop at all. I would address that issue and test again if only to eliminate this from the list of possible causes.

 

I could go along with shock problems, as the shocks absorb to keep the tires planted to the road. Back to tires.
I've seen more than one car and truck to come into the shop for front tire balances, with new tennis shoes on the front, to have the vehicle kicked out the door for the explanation to the tire shop to why the new tires that had been installed and sold are bad.

 

I don't think so. As I said, this car is driven pretty much daily... I don't beat on it, and it worked fine one day and the next it started this vibration. Its just a 260 hp bone stock 350 crate engine and an open rear with a 3.00 gear and 820-15 tires... so it shouldn't have twisted or bent any axles recently.

 

it did this with 8 completely different tires, 10 actually.. because as mentioned above, I tried another pair of rear tires/wheels... all with the same shake at 60.
It's not the tires.

 

If you put the car on stands with the 8.20 tires, spin it up, feel it, and watch, I believe you will see.
The wheel speed will be in the neighborhood of 700 rpm. Gear ratio determines everything behind the transmission.
Drive it with duct tape on the rear tire tread across in one line. See if the offending vibration doesn't match the noise......

 

Take the rears off and spin it.
I forgot something, brake drum....and I can tell stories about that, while diagnosing and repairing.

 

I appreciate the advice, but we took 2 wheels/tires off the back of my friends car that are perfect, his car rolls down the road at any speed without vibration of any sort. Put them ont he back of my car and took it for a ride and the same vibration came on at the same speed.

 

I read you checked U joints, but make sure there weren't any balancing weights that may have came off the drive shaft.

 

Did that too... balancing weight still in place. I'm totally stumped with this... May put a new rear universal in anyhow just to verify... but the one in it now sure feels perfect to me.

 

Following this thread out of curiosity to see what the problem is. Sometimes it's something small. It might be interesting to take video of the wheels, drive shaft and other assorted rotating bits at speed and see if anything shows up. Does the vibration show up at the same speed range if you run it up on jack stands or is it only under load on the pavement?

 

You seem to be able to feel it slightly on jackstands, but way more pronounced when actually rolling. On the 4 lane highway it shakes pretty violently as soon as you get to 60/65 mph.