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Vibration 50 to 65 mph


Hi Everyone, 

 

i have a 72 LeMans that has a vibration I can't seem to fix. It starts around 50 mph but gets worse up to around 65 mph. After that it does smooth out a bit but it's still there. It gets so bad the steering wheel will shake violently and the seats shake as does pretty much the whole car. It seems to be felt more in the seats and shifter but it's hard to tell since the whole car shakes. I have rebuilt the front end completely, had four new tires installed, BF Goodrich TA's 245/60R15. The tires are mounted on factory Rally II rims. The tires were rebalanced twice, and the driveshaft was rebalanced. The transmission was rebuilt last summer, and the driveshaft has new u-joints in it. I also installed new brakes all around (four wheel drums) and new wheel bearings front and rear. I even brought the car to a reputable driveline shop and they can't figure it out either. I have also tried switching tires and that didn't help either. Has anyone else ran into this sort of thing before? I'm at a loss and can't seem to figure it out. I should also note the vibration is there even when you shift the car in neutral and let it coast. The engine is a 400 small block Chevy, with a TH350. Any help on this issue would be awesome thanks. 



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I had a similar problem to this, but coupled with a mild growling noise, worst at 60-65 mph.  After doing everything you did, new tires, wheels, balancing, u joints & shaft balance, ...even new front end parts twice etc.... Still had it even after a change of trans from TH350 to 700r4.  

The solution in my case:  Found the right (old school type) shop and they solved it by a fourth balance and straightening of the drive shaft with high quality U joints - improperly done the previous 3 times.



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65 Custom Sport Convertible

Southern Alberta



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I am actually getting a new driveshaft made next week, the mechanic at the shop I went to figures that's the problem. I hope it is since i have invested a lot of time and money trying to fix this. That's awesome though the guy was able to fix yours.



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Have you thought about removing the shaft and having someone tow you? Risky, I know but it would definately tell the tale...



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Vincent Jr.



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Having operated a Green & Ross Tire for 12 years under the orignal owners.

The company claimed bankruptcy in 1979, so the  Active Tire is not the same, they just bought everything at the auction. 

I am getting carried away....

Find a shop that does on the car balancing.   It is likely only one or at the worst case 2 tire wheel assembly's that are the problem. 

 

We had a car come in for a wheel balance.  It had Quebec plates on it and he complained of a bad vibration.   We brought the car in and pulled the wheels and balanced 4 of them with our Hoffman Balancer.

No noticeable problems as the tire rotated on the balancer...  wheels were straight and no tire hop. 

The customer returned within a half hour and indicated that nothing had changed. 

We put the car on the alignment rack and every part possible had been replaced in the front end.  Something was amiss...

We put the car back on the hoist and used the on car balance and the right front bounced violently to the point it was about to jump off the hoist.  

Took the assembly off and dismounted the tire only to find about 2 quarts of water inside the tire.

As the car got up to speed the centrifugal force kept moving the water to a different place to compensate for the vibration. 

We came to conclude that the customer had added air to his tires from a compressor tank that had not been drained.  He got mostly water and a little air..

Road  tested the car and all was fine.   Our shop was a block away from the 401 so it was easy to get the car up to speed to verify that we had corrected the problem.

One of the most challenging jobs that we got.... 

Keep checking ... you will find the culprit.   Let us know what it was. 

  



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Cliff



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put car on jackstands on rear and run in gear.is it still there then?

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Poncho Master!

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Bent axle? Have someone drive behind you to check the car is not crabbing etc?



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cutting a roof off a four door is NOT a convertible.....

65 Parisienne convertible project.



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67Poncho wrote:

Have you thought about removing the shaft and having someone tow you? Risky, I know but it would definately tell the tale...





I'm sure you have done this when you were a GM tech, we have done it on occasion at the dealership too. Sometimes it's the only way...

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1966 Strato Chief 2 door sedan 283 "survivor"


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Both axles are brand new, since the rear wheel bearings were bad and wore grooves into the axles. So I ended up replacing both the wheel bearings and axles. I did run the car up on jack stands and the vibration was still there. Even the Driveline shop did the same thing and that's why the only thing they can think of is the driveshaft. I will keep you guys posted next week since I am bringing my car in Tuesday to get a new driveshaft built.



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A Poncho Legend!

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Before spending the money on a driveshaft, I would certainly do as Vince suggested, pull it down the road with no driveshaft on it. What if you spend all that money on a shaft and the vibration isn't gone? It's an easy enough test to do and could save you a pile of money.

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1966 Strato Chief 2 door sedan 283 "survivor"


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I just went through the EXACT same thing.

What fixed my issue was an "old school" on the car balance. Worked wonders.

 

Scott



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Poncho Master!

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Bad Trans Mount ?

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Trans mount is new

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Do all garages carry the on the car balancing tool, or is it specialty shops?

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I had mine done at a "TireCraft" here in London. It's a busy tire shop with lots of experienced techs.

The guy who did mine, says it's an "old school" process and not many shops do it anymore.

Might be worth making some phone calls around your town. I'm sure someone will still do it.

 

Regards, Scott (LandShark ...)



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Poncho Master!

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Have you tried popping it into neutral at that speed? Have you done any changes to the rear suspension to alter the driveline angles? And it's definitely speed related not RPM?



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'68 Parisienne 2+2 Convertible Matador Red (Resale Red but not for sale).



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I ran a tire shop for 35 years    one of the key things you said was that it had/has a speed in which it runs well

The suggestions are good ones      running it to speed and putting in neutral can help checking out driveshaft

lots of time a vibration at a certain speed is a "balance" problem  

If you try a set of  "known smooth running " rims and tires, do not change all 4    install one at a time..   when/if the vibration disappears you found the offending rim/tire  

IF thats the problem

 

you have a 400 SBC   is it running a externally balanced ring gear ?



-- Edited by 427carl on Friday 19th of August 2016 08:15:16 PM

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427carl 

 

 

you have a 400 SBC   is it running a externally balanced ring gear ?



-- Edited by 427carl on Friday 19th of August 2016 08:15:16 PM


 Good point  Carl. And that's where I was going with the RPM thing. These engines are externally balanced. I have seen it before with wrong flexplate. Should vibrate in neutral same RPM. 



-- Edited by JC2+2 on Friday 19th of August 2016 08:32:46 PM

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'68 Parisienne 2+2 Convertible Matador Red (Resale Red but not for sale).



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Just another wild guess, but years ago I bought a Chevy 1/2 T with a bad shake.

I had another truck the same so I could easily swap parts to isolate the problem.

After swapping everything back and forth, and it still shook, I noticed the rear brake shoes were installed incorrectly.

I don't know how this caused the shake, but it was fine after reinstalling the brake shoes.

That's the long and short of it!!!

Thanks
Randy







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Sherwood Park
Alberta, Canada

1981 Parisienne 400



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The engine does have an externally balanced flex plate, and as far as I can tell the harmonic balancer looks good. I forgot to mention that I did switch tires over before. I borrowed a set from a buddy of mine who had a 69 Olds Cutlass. The vibration was still there. Also when you are driving on the highway the vibration is still there even if the transmission is shifted to neutral, and you cost in neutral. Thanks for all the input really good ideas.

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As Carl said try switching one tire at a time.
Ciiff


You need to isolate the problem.

It is a bit of work, but I believe you will see results.

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Cliff



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One last thing I would try is take about two or three 4" hose clamps and put them all side by side in the middle of the drive shaft. Once snug take it for rip. Did the vibration change? Move the "weights" hose clamps about the length of the tightening screw and retest. Do this until the vibration disappears or you have gone full circle.

This procedure will eliminate or prove the drive shaft is the culprit of the vibration.

Another test I would do is jack the car up so a tire can spin freely. Place an item close to but not touching the tire. Spin it to so if there is any runout. Even with new parts something may still not be true.

Best of success in your trouble shooting.

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Eric - Regina, SK

The Projects:

1935 Chev 3 Window Std Coupe

1967 Mustang Convertible

1969 Firebird 350 HO Convertible

1969 Camaro X11-V8 car

1969 GTO

1969 Parisienne

1969 2+2 was a 396 car

1978 Chevy Short Box Step Side 4x4

1980 Harley FXWG

1986 CJ7 Jeep

 



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lotsa great suggestions another check that comes to mind is removing the fan belt and run in park at crusing rpms or drive around block and check but not too far lol

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Hey Guys,

So a quick update on the vibration issue, did a couple things over the past few days ie: switched tires around to try and isolate the wheels, however I did notice that when I brake that there is a slight vibration as the car slows down. So I am wondering now if maybe a wheel cylinder may be sticking, not allowing the shoes to fully retract. Switching the tires around didn't cure the vibration unfortunately, I also did notice that the tires do not run true as well, when I had the car up on jack stands. So now as a result I am suspecting the tires and or brakes to be the culprit for this vibration. Will update further if I can fix the vibration.

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If your tires aren't running true, I'd focus on that. Narrow it down to wheel, tire or hub and work on the root problem. Out of round drums might cause a problem - especially if they were warped and then machined. They might be true inside on the wear surface, but if they were badly warped before being turned, they may have significant variation in thickness which would throw off the balance and they would likely warp after a heavy use.

The on-vehicle balance would solve out-of-balance drums/rotors, but you'd have to reinstall the wheels back on the same axle, with the same orientation or the balance would be ruined.

Off the wall suggestion: make sure the mating surface between the wheel and hub is clean and flat. I've seen bits of slag or rust embedded into the back of aluminum wheels or stuck to steel wheels/hubs.

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