63 Front end shimmy/shake

[Harry S.]

Greetings all, Ive been fighting this shimmy/shake in my front end for the past 18 months. I've listed below what I have done and what I could possibly still do.

It was really bad between 57 and 64, now it's there pretty good at 62 mph.

Any ideas/suggestions would be helpful.

Completed Changes

• Front wheels balanced
• Front wheels balanced on car
• Rear wheels balanced
• Borrowed four wheels and tires from a smooth running 65 convertible, same problem
• Replaced front bearings
• Replaced front drums
• Replaced rear drums
• Replaced rear trailing arms & bearings (they were bad anyway)
• Front wheels balanced again
• Align front end
• Replaced front shocks
• Replaced tie-rods and ends - 8/31/2008
• Replaced idler arm - 9/1/2008

Changes still to do?

• Replace lower ball joints
• Replace upper ball joints
• Rebuild steering box
• Replace front springs
• Align front end
• Slit my wrists

[Martin N.]

Re: 63 Front end shimmy/shake

HARRY-
Front wheel bearing torque was checked? Any changes to the drivetrain over those same 18 months? U-Joints, Axle Joints, Clutch, etc.

Marty

P.S. I don't think the wrist thing will help,even if your car is red on red.

[Donald T.]

Re: 63 Front end shimmy/shake

Have you checked to see if a balance weight has fallen off the driveshaft? Have you tried orienting the driveshaft 180 degrees from the present position to see if it is out of phase?

[Joel T.]

Re: 63 Front end shimmy/shake

Harry;

I would check the driveshaft as well.... What rear axle ratio do you have in there?? I changed my 1963 from a 3.36 rear to the correct 3.70 rear. The car started shaking like crazy. Scary bad... Found a guy here in NJ who balances drive shafts. Spent like a $100 on getting the drive shaft rebalanced and now she is as smooth as a baby's behind! Drove the car about 120 miles yesterday, averaged about 70 MPH, and it was SMOOTH! (passed a 396 Chevelle, and a 1964 Vette in the process)...

Hope this helps,

Joel

[Harry S.]

Re: 63 Front end shimmy/shake

Marty, Don and Joel, no changes to anything in the last 5 years. I felt around the driveshaft today and it does not appear that anything is missing.

I'll do the ball joints next, since I have them, then maybe it's time to pull the driveshaft and have it looked at.

[Donald T.]

Re: 63 Front end shimmy/shake

Marty, Don and Joel, no changes to anything in the last 5 years. I felt around the driveshaft today and it does not appear that anything is missing.

I'll do the ball joints next, since I have them, then maybe it's time to pull the driveshaft and have it looked at.

Harry,

Since the vibration occurs at a certain speed, it sounds like an harmonic vibration. This would tend to indicate a balance issue somewhere in the drivetrain. Since it is speed related and not RPM, it would indicate an issue after the transmission. Since you have already eliminated wheels and tires, that leaves the most likely culprit of an unbalanced driveshaft. Just rotating the driveshaft may put it back in phase, and if the vibration changes then you will know you are on the right track.

Here's a question that I don't know. If you replace the driveshaft with a new one, are repro driveshafts already balanced? If one replaces the slip yoke and the driveshaft, is it still necessary to have the assembly balanced as a unit? Seems like just replacing the driveshaft ($135 at LICS) wouldn't cost much more than having the old one balanced.

[Werner R.]

Re: 63 Front end shimmy/shake

follow-up question:
i have the same shakes between about 60 and 65. however, mine keeps shaking even if i put it in neutral and let the car coast at same speed. that sounds to me like the engine and everything behind it are out of consideration. am i correct on this??? would this indicate front wheels or suspension?

[Harry S.]

Re: 63 Front end shimmy/shake

Werner, I have to try that and see what happens.

As soon as you disengage the clutch and put it in neutral, the engine is eliminate as well as the clutch and most of the trans internals from the driveshaft. The driveshaft will continue to turn.

[Duke W.]

Re: 63 Front end shimmy/shake

Make, model, size of tires?

Out of balance or round is almost always the cause of these problems. Worn suspension components can make it more sensitive, but are not usually the root cause.

Have you had the wheel/tire assembies checked for runnout on a Hunter 9700?

My SWC was always very sensitive to wheel balance and runnout. The slightest amount would cause the front end to shake.

When I had my body off the frame the front end fiberglass seemed very flexible in torsion. Further investigation revealed that the bond of the RH inner fender panel was mostly broken - or never took hold.

Repairing that bond stiffened up the front end an amazing amount, which considerably raises the natural torsional freqency of the front end fiberglass, making it much more resistant to shake with the slight residual out of balance/round that is inherent to all wheel/tire assemblies.

Given that the other set of wheels/tires that ran smooth on the other car caused the same problem on yours, this might be something to look into.

The natural frequency of the front suspension corresponds to the rotational frequency of the tires at about 60 MPH, so this is where any slight unbalance or out of round will resonate with anything else that has a similar natural frequency. In my case it was "loose bodywork".

Duke

[Stuart F.]

Re: 63 Front end shimmy/shake

My second set of tires (Goodyear 7.75 x 15's) apparently had a broken belt and it drove me and a few shops nuts trying to find it. It would only show up at around 50 to 55 MPH. They were new too, so who would expect it. When a friend tried a spin balance on the car, I thought it was going to jump off the jack. He pin pointed the tire and I finally got Goodyear to replace it.

Stu fox

[Gerald L.]

Re: 63 Front end shimmy/shake

I second the Hunter 9700 balance. I am a former Miata driver, and solo enthusiast; those cars were notorious for tire induced issues at a narrow speed range. First advice was always find a shop with a Hunter 9700 machine, no other machine considered; then test the car again.

[Harry S.]

Re: 63 Front end shimmy/shake

The tires were done on a Hunter. There is something else going on. I swapped all for wheels and tires with a 65 smooth running vette and I had the same problem. I do not believe it's the wheels and tires.

[Chuck R.]

Re: 63 Front end shimmy/shake

Harry, is the wheel shaking side to side or more of an up and down bounce?

Do you feel it more in the seat of your pants or more at the steering wheel?

[Al S.]

Re: 63 Front end shimmy/shake

Harry,
I'd pull the drive shaft first and at least check the u-joints, it's easy enough to do. (before you go ripping into the ball joints)
It seems you've eliminated many of the items you'd normally go to first.
A stiff u-joint will give you a vibration also but usually in the seat not the steering wheel. Again, that can easily be checked along with some of the other members suggestions while the shaft is down.
I'm assuming you feel the problem in the steering wheel according to your first post?
Good luck.
Al

[Harry S.]

Re: 63 Front end shimmy/shake

Chuck and Al, the shaking in the steering wheel is more up and down vs. side to side. You can see the front-end shake as well as the rear view mirror.