Trying to track down steering wheel shimmy .

[Canadian1968]

My 68 R/T had the entire front end totally torn down and put back together. Brand new bushings , tire rods , ball joint. Rebuilt factory steering box, shaft and coupler.  Tires just re balanced.

I am getting shimmy in the steering wheel as I approach 50-60 mph, inconsistently.  Depending on load , and drive time.  So if I take it for a drive the first 5 -10 mins the car seems to drive perfect.  As I drive it longer  I start to feel a shimmy in the steering wheel  and can be felt threw brake pedal when slowing down, this seems to get worse the longer I drive it.  If I accelerate harder I don't feel it at all.  The car is a factory disc brake car. New bearings and races where installed, and the disc were cut fresh.  I tired re tightening the wheel bearings, going a little tighter on the torque before backing off 2 slots in the lock nut. This seemed to help a lot, only a very slight shimmy could be felt.  But after about a 30 min drive. I got out and felt the front hub, its is pretty damn hot , I can touch it for about 3 secs before I have to take my hand off.  I let off the lock nut 1 more notch, shimmy is more noticeable and hub is still very hot.

The car has a slight pull to the left.

And when re balancing the tires we noticed a slight skip in one of the rims but it did balance out fine.

Thoughts ?  I am thinking of pulling he rotors and checking the bearings.  

[cdr]

backing off 2 slots is WAY to loose.

[Canadian1968]

those are the instructions as per FSM

[PlainfieldCharger]

Are you sure you got the bearings seated correctly?       

[charger Downunder]

Front strut rod bushes are they tight. You didn't forget to grease/ pack the bearing before install.

[TommyGun]

A sticking caliper can cause this, or a brake hose that wont release.  The longer you drive the worse it gets. When you come back from a drive jack up the front end and see if you can spin the tire with ease or is it hard to turn. It would explain the pull to the left also. Also I have found that once a rotor is warped, even if you turn them the pulsation can come back.

[Canadian1968]

Are you sure you got the bearings seated correctly?       

I am wondering if I never got then seated correctly the firat time.  Best way to make sure is to pull the rotor completely off check and reinstall ?

[PlainfieldCharger]

This is what I do...jack up the wheel in question so the tire is off the ground. Take off the hub cover remove cotter pin and locking star washer..Get a wrench or socket that fits the nut ready to go. Spin the tire and tighten the nut nut until the tire stops with resistance.  Back off nut until tire spins freely again. Spin tire again tighten nut and just when you see some resistance Thats is where you lock in the star washer with the cotter pin. Your up and down wheel end play should be barely noticeable. when compared to a fixed point.   

[Canadian1968]

I was worried that I had them to tight...  Its ok if the hub , get pretty hot?

[PlainfieldCharger]

They should not get hot..I would say warm is ok after 5 miles....I would put my hand on both hubs to make sure they are about the same. You should be able to touch them...  
Depending on how hot it got you might want to re-grease the bearings....

[Canadian1968]

well pulled the rotors. Everything looks fine , grease does not smell burnt at all. Brake pads wearing even. I Packed the bearings again and  put everything back together . Borrowed a nice digital torque wrench. Spun the rotor and torqued down to 10 ft lbs . Backed off half a turn , spun the rotor and torqued back to 8 ft lbs . I put on the star nut and dropped in the cotter pin.   Installed everything , everything spins very nice . Will see how she drives !

[WhiteOnGreen]

Service manual say no preload to 0.003 end play 

[375instroke]

Is caster near zero, or negative?  Could this be the problem?  Perhaps toe, also.  If it's right on the edge of pushing the tire in one direction or the other, I would imagine it could shimmy.  The stock settings suck.  Go for as much positive caster as you can get, and definitely no positive camber.

[bakerhillpins]

I was going to bring up a broken belt but since you have tried re balancing again I don't think that's the issue.

backing off 2 slots is WAY to loose.

Agreed! adding another is even worse. I'd be thinking about replacing the bearings at this point.

A sticking caliper can cause this, or a brake hose that wont release.  The longer you drive the worse it gets. When you come back from a drive jack up the front end and see if you can spin the tire with ease or is it hard to turn. It would explain the pull to the left also. Also I have found that once a rotor is warped, even if you turn them the pulsation can come back.

I'm with Tommy on all of his points. As he mentions, brake hoses can fail internally where the interior liner collapses and can lock the brake on. I wouldn't ignore the rear drums.

Nothing against PlainfieldCharger but I go with the manual specs of 90in-lbs and back off one hole as shown in attachment.

[Canadian1968]

well I finally got a chance to take the car out again. And it felt great , no signs of a shimmy at all. Not quite as long of a drive as before but if it was still there in would have noticed it. The hub was MUCH cooler when i got home, outside temp was a bit.cooler than last time as well but not enough to make that much of a difference .

So the problem seems to be gone , I cant say exactly what I think the problem was but bearing related