Plymouth P-6 drag link

[atlbluz]

I am trying to get rid of a terrible shake, shimmy, vibration whatever.  I have purchased a new set of tires from that TN tire dealer and that has not helped my shimmy-shimmy shake at 35 MPH.  The old tires were 35 years old and sat for a long time, so I figured that was the problem.

We have balanced the tires off the car, on the car, with new road force equipment, still cannot get over 35 MPH.  While we were doing the road force balancing

we checked the link pins and tie rods.  They seemed to be within tolerance.  the drag link seems like it may be a little loose.  I get about 1/4 to 3/8 inch movement at the front of the tire.  So is the drag link adjustable or do I need to put a rebuild kit on it?  I never rebuilt the drag link the first time I restored the car

and it would go well beyond 35 MPH.  Greg

[Don Coatney]

Have you inspected your rubber engine mounts for and aft? Have you inspected your driveshaft and universal joints?

[Robert Horne]

!/4 inch movement on a drag link is a lot.

 

1/8 inch would be a lot also...

 

My 38 has very little movement.

[atlbluz]

Have you inspected your rubber engine mounts for and aft? Have you inspected your driveshaft and universal joints?

Don, most of the vibration is coming thru the steering wheel, do you still think it might be motor mounts?

[atlbluz]

!/4 inch movement on a drag link is a lot.

 

1/8 inch would be a lot also...

 

My 38 has very little movement.

Robert the 1/4 inch is at the tire, not the link, but is the link adjustable?

[Don Coatney]

Vibration usually comes from rotating equipment. You have replaced and balanced the tires. Drag link does not rotate. Engine mounts do not rotate but if they are severely collapsed they can cause miss alignment in the driveshaft and that can lead to vibration when spinning. Most all vibrations can be felt in the steering wheel because that is where your hands are located.

[rhelm1953]

Can we better define what you mean by a terrible shake, shimmy, vibration? Understanding what you are feeling will go a long way to rule out what is not causing the problem. When you experience the vibration does the steering wheel jerk side to side? If it does then we can rule out a driveline problem and focus on the steering and wheels. If the steering wheel does not jerk side to side but you can feel a vibration in the wheel does it change with vehicle speed or engine speed, is it the same if you go 35 in 2nd gear or 3rd gear? If it varies with engine revolution then it's in the engine and could be motor mounts or an engine driven accessory, if it varies with vehicle speed it could be driveshaft or tires.

Give us a better description of the problem and we can give better guidance on where to look. The free play you describe at the front wheels does sound like a lot and if your alignment is off could help set up a vibration, in that case you would probably feel it as a back and forth movement in the steering wheel.

Better information = better help :-)

[atlbluz]

Can we better define what you mean by a terrible shake, shimmy, vibration? Understanding what you are feeling will go a long way to rule out what is not causing the problem. When you experience the vibration does the steering wheel jerk side to side? If it does then we can rule out a driveline problem and focus on the steering and wheels. If the steering wheel does not jerk side to side but you can feel a vibration in the wheel does it change with vehicle speed or engine speed, is it the same if you go 35 in 2nd gear or 3rd gear? If it varies with engine revolution then it's in the engine and could be motor mounts or an engine driven accessory, if it varies with vehicle speed it could be driveshaft or tires.

Give us a better description of the problem and we can give better guidance on where to look. The free play you describe at the front wheels does sound like a lot and if your alignment is off could help set up a vibration, in that case you would probably feel it as a back and forth movement in the steering wheel.

Better information = better help :-)

No the steering wheel does not Jerk.  it's more like when a tire is out of balance.  It is road speed related not engine speed.  I di not pick up much of this vibration in my butt, so I have always been told that a rear end vibration or the like comes thru the seat.  As I approach about 40 MPH the rear view mirror is vibrating so badly that you can't see out of it and the side mirrors are about the same.  I hope that helps.

[Plymouthy Adams]

even new tires can be out of round....out of round tires can be balanced but never run smooth....have you also considered your rims for being straight and true...AND...check and see if by looking you notice that a brake drum may have slung a balance weight.....look for signs of detachment.....

[Robert Horne]

There are many parts to the suspension.  

If any one or more has play, you will have a problem.

Try jacking up the driver side of the suspension with a floor jack.

See if the tire will move left or right, up or down, or tilt in or out.

I changed my king pins years ago, the driver side had a little play.

[DJ194950]

Another way to check wheel/tire straightness is to jack up front of car with tire just clear of ground and take a wood block and place at side of the tire and slowly rotate tire/wheel moving the block very close to the side of the tire. Does it move in or out away from block? If so put a straightedge higher up on block to hold against the wheel bead area of the wheel rim to see if the tire is the problem area or the wheel. OK,? Then move block just in front of the tire and rotate tire and make a center line scribe with a pointer of some point and see if tire run true and then also watch from the side to see if the tire runs out of round. Really only takes a minute or two.

 

Repeat one wheel/tire at a time, front repeat steps on the rear. Less than 20 minutes total when the test is completed.

 

Just helps with this easy/quick test before moving on to other Good ideas already posted.

 

Best,

 

DJ

 

 

 

O

[TodFitch]

Robert the 1/4 inch is at the tire, not the link, but is the link adjustable?

 

If it is built like the one on my '33, yes there is a bit of adjustment. But. . .

 

There are many parts to the suspension.  

If any one or more has play, you will have a problem.

Try jacking up the driver side of the suspension with a floor jack.

See if the tire will move left or right, up or down, or tilt in or out.

I changed my king pins years ago, the driver side had a little play.

 

 

Chances are with 1/4" to 3/8" play at the tire you have a number of worn items. As Robert suggests, a careful inspection and repair/replacement of all out of spec parts may be needed, not just a drag link adjust.

[RodFru2u]

 I have run across out of round tires before, Once mounted the tires were " marked " then he brought out a machine and shaved  them perfectly round  on the rim. He ID each side and made sure we knew not to rotate. Made all the difference, could not get to 35 mph before major shake and shimmy after  was able to get up to freeway speeds ( 55 - 60 )  no problem.

[deathbound]

Here's my thread when I rebuilt my front end on my '38 Plymouth Coupe:

http://p15-d24.com/topic/26625-new-front-disc-brakes-front-end-rebuild-steering-rebuild-for-the-38-plymouth/?hl=%20front%20%20end%20%20rebuild

Been a while, hope it helps.

[BigDaddyO]

Sounds like king pins to me.

Raise the tire clear of the ground. Grab the tire at the 6 and 12 o'clock positions or slide a pry bar under the tire from the side and rock the tire in and out.... does it clunk or feel loose?

if it does ; have someone hold the service (foot) brake.... then try to rock the wheel again. if it still feels 'loose' the king pin/bushings is likely the cause. if the play went away when you applied the brakes, the cause is more likely wheel bearings... check the wheel hub for 'sparkly' oil

if you're still uncertain, have someone grasp the top of the tire (with a tire bar if necassary) and attempt to rock it inward and outward. in the mean time, you crouch down at the inboard side of the tire and watch for movement between the steering knuckle

Edited August 17, 2016 by BigDaddyO

[atlbluz]

even new tires can be out of round....out of round tires can be balanced but never run smooth....have you also considered your rims for being straight and true...AND...check and see if by looking you notice that a brake drum may have slung a balance weight.....look for signs of detachment.....

PA I am going to check for the tires and wheels this weekend.  But when the front tires and wheels were on the balance machine they did not seem to have an appreciable wobble and the Hunter 9700 did not indicate the wheels were out of round.  I did not sling a wheel weight because they still vibrated immediately after leaving the tire store.

[Plymouthy Adams]

when you do not know what is wrong...prove what is right...this is the only way to eliminate an item from the equation...many good suggestions listed..make a list...as you prove one is not the problem..mark it as such ...

Edited August 17, 2016 by Plymouthy Adams

[atlbluz]

I stated weight on brake drum...not the wheel when balanced...

OK I will check that, but I also had the fronts balanced on the car and with them 'in balance' I still couldn't get above 35 MPH.  So I thought out of round, Coker said to put them on the Hunter 9700 road force balancer.  Still 35 MPH max.  The tire store front end guys looked at the play in the front end and thought all was within spec.  So this weekend I am going to jack up the front end and put my dial indicator to good use and see if or how much the tire is out of round.

[Plymouthy Adams]

not all drums will have weights attached..just threw that out as a general overall tire/balance issue....I work more cars than just these older babies here...

[Niel Hoback]

Put the rear tires on the front and see if it still wobbles.

[BigDaddyO]

  So this weekend I am going to jack up the front end and put my dial indicator to good use and see if or how much the tire is out of round.

Dial indicator seems like overkill.

[Plymouthy Adams]

for giggles....tell us how much weight is on each tire..inside and out...and who is that TN dealer...as if I have to ask.....lol 

Edited August 17, 2016 by Plymouthy Adams

[DJ194950]

Is your "wobble" above 35mph felt in the steer wheel shaking or the whole car sensation?

 

When I redid my 50Ply. brakes I had a similar problem. Turned out to be a rear wheel running out. Traced to the rear hub was not on straight. Still very tight, but had nicks in the key /key way of the axle/ and the hub itself. Cleaned everything up reinstalled with some anti-seize and all was well again.

 

Hope it's some easy and cheap for you also! 

 

DJ

[BigDaddyO]

When did you first restore the car? What has been done to it since?

 

  I never rebuilt the drag link the first time I restored the car

and it would go well beyond 35 MPH.  Greg

[BigDaddyO]

Whatever happened here? Did you figure out the cause of your vibration?