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

Gonna be interesting to find out what you eventually nail down as the cause. But as I posted originally it doesn't seem as if you have tied down whether it is a high frequency like Drive Shaft or Tire issue. There should be a huge difference. Did you check your spindle nuts and front wheel bearings? Seems like we are all just starting to make wild-ass guesses hahaha

 

Did you remove the driveshaft and then check the universals? I have had them seem tight on car but when shaft was removed you could feel it catch as you moved them through their range of motion.

 

Yes, had driveshaft out, universals seem perfect. That's also when I checked the pinion backlash and it has a bit more than I'd like, but honestly don't think it would cause the 60 mph vibrations I'm getting.

 

It definitely seem like a driveline related problem. Is there any slop at the transmission end? Had a sliding yoke with wear in the splines that caused problems. What transmission?

 

Something got bent or loose at some point to suddenly cause this. You've got new tires, but temporarily swap out all the wheels too to eliminate a slight bend there. I like the suggestion to check the transmission tailshaft bushing. Or maybe the yoke is slightly too far out and the worn bushing is allowing the wobble. Or it probably wouldn't hurt to fix those loose kingpins now.

Then, go around tightening ALL bolts, rod ends, screws, etc. take out those cotter pins and tighten up the stuff you think would never come loose. Especially steering and suspension parts.

 

A too short driveshaft will cause a driveshaft frequency vibration when decelerating. It would feel like a bad u-joint.
The only driveshaft vibration I have ever witnessed that was bad enough to cause exhaust to blow loose was on a Peterbilt truck that someone had "repaired" the driveshafts and used .134" wall tubing instead of .180 wall. Result, was the vehicle weight and engine torque causing a twist that you could follow by the weld seam, and bends in both shafts to the tune of 1/4". And the driver brought the truck to the shop after a 150 mile drive! It's a wonder he had a transmission synchro left! The weight of the shafts shook the hood and stacks at 15-20 mph, and was tee-total hell at 45 mph!
The same theory applies to a hotrod, depending on gear ratio.
My tire problem on the front of my A hotrod was a condition that everything was great up to 65 mph. Then at 70-75, the front end would jump and shake hard enough to break the radiator support rod bracket and bend the support rods.

 

What about the motor mounts? with 39 thousand miles on the odometer a broken motor mount or a transmission mount can cause a sudden unexplained vibration.

Worn king pins can also contribute to the problem. HRP

 

Not been any mention of motor or trans mount failures thus far? Mentioned for elimination purposes!!!!!

My personal experience of such things is limited to wheel bearings, universals, tailshaft bushes, wrongly adjusted toe (after new axle and spindles fitted), engine and trans mounts but tires going bad in a short time was the most notable and rear wheel bearing the hardest to find.

Running it on stands to find the vibe still there to an extent does seem to eliminate front end issues. You could run it on the stands with no rear wheels (elimination purposes) and check the wheel bearings with a stethoscope / dowel etc.

Chris

 

ha ha, must type faster!

 

Have you checked your pinion/driveshaft angles?

 

Trans bushing at tail shaft? My son had an O/T car with 2oo4r. bad vibration at 60-65. tail shaft worn. like said above check Motor mounts.You absolutely sure its drive line related? still would check front Wheel bearings. Keep us posted.

 

I know you have changed wheels, but is there anyone around you that does strobe lite balancing? You know some one at tire store who can spin the wheels on the car. lay a hand on car while spinning.Its just a aggravating process of elimination. Again good luck and keep us posted.

 

I'm not absolutely sure of anything... I do know the shake can happen even coasting in neutral. Ordered new kingpins and bearings today, as well as a new tie rod end that had the slightest bit of play. Honestly don't think it'll fix my shakes, but needed done anyhow. Considering trying to borrow a pair of front wheels/tires from someone and try that... I know swapping rear wheels/tires didn't help.

 

I think you are on the right track with the front end parts.

I sense the problem is much more noticeable when driving than on jack stands, so that largely rules out drive train vibration.

I recently replaced kingpins that didn't seem that bad. Made quite a difference in the steering wheel feedback at freeway speeds.

Phil

 

Sounds like a bunch of stuff had "a bit of play" could be a cumulative effect of all the little bits.

 

Plastic bushings in rear suspension can fail and change the pinion angle. That would do it.

 

A few updates... Had 3 different guys (all mechanics) drive it, and 2 out of 3 believe it's originating from the front end. It's so weird, because you can feel it in the whole car... It's more of a "shake" than a true vibration, and comes on at about 60, but seems to never really go away above that speed. It's also much more noticeable in the drivers seat than it is as a passenger. You can feel it in your accelerator pedal, in the wheel, and in the seat of your pants to an extent. As a passenger you feel a little shake in your seat, but it doesn't feel nearly as violent as when you are at the wheel. It is more prevalent under load, but the shake can happen when coasting too, including during deceleration while coasting. If you never get to 60mph you'd not know there was any issue at all. I ordered a new kingpin set today, and won't get it til Friday or Monday, so hopefully next week I can get this thing sorted out.

 

Need to find a machine shop that can press the bushings into your spindles. Then align hone the bushings to fit (accept) the kingpins. Hope this helps.

Phil

 

I actually decided to take that potential hassle and error out of the equation as well, and ordered completely new spindles with bushings installed and kingpins pre-fit.

 

Still doesn't explain why the exhaust hanger broke. Flies are still a buzzin'....

 

Well, that MAY have been from the vibration, or may have just been coincidence, as the same hanger on other side had broken about a year earlier in the same spot. One of those rubber strap hangers that simply dry rotted from heat and let go after 10+ years. Don't think its related to the shake I have, but may have been caused by it.

Trust me, I'm personally NOT convinced the kingpins are causing all of this, nor am I even conviced for certain that the shake is totally originating at the front of the car... but they definitely have more play in them than they should, and replacing them is a good idea regardless. Hopefully when it's back together the shake will be gone, but until then there's really not much else I can think of to check. Heck, I even took it out today with the rear brake hose clamped off and no rear brake drums on it to eliminate someone's idea that it may be stemming from the drums being out of balance. (they weren't.) Also gave it a tune-up with new cap, rotor, plugs and wires to be sure the engine was running as smooth as could be. If nothing else, It's getting some 40,000 mile maintenance.

One thing I promise though, is I will follow up with my findings, and when and if I ever get this figured out and fixed i'll report back as to what it ultimately was. I hate it when I look through threads like this and never hear what the actual cause was after 1000 theories and suggestions of what it might be.

Thanks to everyone who contributed, and feel free to keep the ideas a comin'.

 

Gremlins.......for God's sake, don't ever get them wet.

 

FWIW, I once had a Pontiac GTO that had a vibration that started around 60 MPH, eventually the vibration could be duplicated by reving the engine. As the car was under warranty, I took it back to the dealer and told them I thought it was the water pump. They test drove the car and said no the torque converter was at fault. Dropped the car off as they were going to replace the 400TH transmission. When I went to pick the car up they said it wasn't ready yet as they were still changing the water pump. I said "it the water pump after all wasn't it"? They replied no it was the transmission but we're replacing the water pump as a precaution. Yeah right.

Gary

 

Woa! Re-reading what you've said previously and realise you've tried alternative rear wheels with tires and you've rebalanced all 4 of your own wheels, and on that basis you've eliminated the wheels / tires being a possible source, right? Wrong! You need to have your tires road force balanced (Hunter - look it up) which balances the wheels when moving but with the contact patch loaded - significantly different from a mere rotational balancing. This helps reveal tires breaking down internally. Or just replace the front tires.

Admittedly I have no first hand experience of this but have fixed exactly the same problem as yours by having the front tires replaced with new after having checked out seemingly everything. My shake came on quite quickly during a road trip - started out perfectly but became undriveable over 60 or so after about 6 or 700 miles into the trip. Realistically it might have come on in no more than a couple of hundred or so. It ruined about half a day on the road.
Chris

 

Doesn't this comment suggest shocks ?

 

Well, I've been struggling for 2 weeks with this, trying to even pinpoint for sure which end of the car the shake was originating for sure. After driving it 100 miles last Saturday I was certain that the shake was amplified when accelerating, and diminished when the car was in neutral, although it didn't completely go away. When accelerating up a hill from about 60 mph on, I could feel a shake or quiver in my gas pedal foot, a shake to the steering wheel, and a vibration in the seat of my pants. I was almost certain it was drivetrain related, because if it were tires or front end components, it wouldn't ever diminish in severity by taking the car out of gear. WRONG! Read on....

After debating with a buddy (who is also a mechanic by trade) he suggested I replace my worn king pins and bushings. I agreed, because they have had some play in them for several years... but I 100% did not believe this was going to fix or even have anything to do with the shake I was experiencing at 60 mph and up. The car never quivered over railroad tracks, never wobbled at low speed, and until last week, never had any sort of vibration even as fast as 85 mph. Well, long story shorter... it fixed it! I took it out for a ride this afternoon after replacing both kingpins, and it drove right up to 80 mph without a shake.

I do still have a drivers side tie rod end with a little play in it that I am going to replace tomorrow, as well as a steering universal with similar play, but the shake seems to be gone with the replacement of the kingpins...which quite honestly didn't seem to be worn any more than they've been for years...I guess they reach the point where they go from "good enough" to not so good pretty quickly... I owe my buddy a steak dinner because I bet him that replacing them wouldn't cure anything and it did!

So for future reference, if anyone tells you worn kingpins can't cause a high speed shake with no signs of issues at lower speeds, tell them they most definitely can... in fact, bet them a steak dinner on it!

 

Great to know, that is a bet I'll put in the bank. I'm sure you're one happy hot rodder to have finally found that gremlin.

 

Thank you for following up with what you found to be the problem and how you fixed it.

 

Sorry to resurrect an old post, but this may have solved my problem!! I have an oscillating shake above 60 that has gotten worse. Just checked my king pins and the passenger one has a good bit of slop. Will replace this weekend and report back.

 

Mine has the same problem and it turned out to be king pin bushings just loose enough. Seems I slipped into modern car syndrome" and forgot to lube them as often as we used to. Had a had time finding just the bushings, but Magnum Axle has them on the shelf.