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MikeNZ

CCKW steering shakes at speed?

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Hi All

 

At between 35 -45mph my 1942 CCKW gets a bad case of the shakes - Violent shuddering side to side. Hitting a expansion joint produces such severe motions that it is difficult to hold the wheel. A side to side motion is the best way i can describe it.

 

Thus Far:

 

New Draglink

Balance & Alignment.

 

It only occures at 35+ - Below this & the trucks handles correctly and drives true & straight,

 

Any Ideas?

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Hi All

 

At between 35 -45mph my 1942 CCKW gets a bad case of the shakes - Violent shuddering side to side. Hitting a expansion joint produces such severe motions that it is difficult to hold the wheel. A side to side motion is the best way i can describe it.

 

Thus Far:

 

New Draglink

Balance & Alignment.

 

It only occures at 35+ - Below this & the trucks handles correctly and drives true & straight,

 

Any Ideas?

Sounds very much like 'Wheel tramp' can be caused by a combination of components associated with suspension or steering or a combination of ware in both areas.

The 'death wobble' which is the colloquial term for this problem has attracted the name for good reason. causes casn be any one or a combination of the following some of which you may already have covered, either way if it's as bad as you imply in your post it needs sorting quickly.

 

Flat spots on the tyres

mismatched tread pattern

uneven or badly worn tires

Out of balance wheels/tires (for what ever reason also see combination of above)

Worn spring shackles in frame/spring eye/ bush

Loose spring saddle / U bolts loose/broken

Broken spring leaves

worn/missing shock absorber bushes

Failed/frozen or empty shock absorber on one or both sides

Worn king pins/ failed carrier bearings

Worn track rod joints

Bent track rod

Worn/bent drag link

Bent/worn drop arm

Steering box/linkage out of adjustment

Worn components in the steering box

 

Pete

Edited by Pete Ashby
missing word

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In my experience under inflated tyres will give those symptoms at those speeds. Because the side walls are so stiff the tyres won't appear to be under inflated. In my opinion a good quality tyre pressure gauge is an essential part of a tool kit.

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I'm wondering like Degsy about tyres. You say it only happens at high tempratue? The only thing that comes to mind that would change is tyre and pressure. What type , age and condition are they maybe a sign of a tyre wall failing?

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Tony, you need to visit Specsavers or get yourself a white stick and a Labrador,:n00b: there is no mention of temperature in the thread.:-D

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Often the cause of wheel shake on a 4x4, or in this case 6x6 is worn bearings in the swivel housings on the ends of the front axle, these bearings have to be tightened to a determined preload using shims so the swivel bearings are under pressure and offer resistance when moving the steering swivels, they have a damping effect, if they are worn and there is insufficient resistance then wheel shimmy can occur

 

Previous post about a GMC with same steering shake problem and new swivel bearings which cured the problem

http://hmvf.co.uk/forumvb/showthread.php?3453-GMC-Truck-Steering&p=35373#post35373

Edited by Nick Johns

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Tony, you need to visit Specsavers or get yourself a white stick and a Labrador,:n00b: there is no mention of temperature in the thread.:-D

 

looking at 35+ thought in NZ that might be tempeture rather than speed. :-D Funny place for temprature New Zealand, the only place you can walk up a glacier in a rain forest!

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Hi All

 

At between 35 -45mph my 1942 CCKW gets a bad case of the shakes - Violent shuddering side to side. Hitting a expansion joint produces such severe motions that it is difficult to hold the wheel. A side to side motion is the best way i can describe it.

 

Thus Far:

 

New Draglink

Balance & Alignment.

 

It only occures at 35+ - Below this & the trucks handles correctly and drives true & straight,

 

Any Ideas?

 

To rule out misshaped tyres or a buckled rim , swap the fronts with the best pair of equal looking tread you have on the rear end , that then will either prove it's tyres or rims , but if shuddering still persists then it will be mechanical wear.

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Hi All

 

At between 35 -45mph my 1942 CCKW gets a bad case of the shakes - Violent shuddering side to side. Hitting a expansion joint produces such severe motions that it is difficult to hold the wheel. A side to side motion is the best way i can describe it.

 

Thus Far:

 

New Draglink

Balance & Alignment.

 

It only occures at 35+ - Below this & the trucks handles correctly and drives true & straight,

 

Any Ideas?

 

Has the shake suddenly started or has it been getting worse until it is now a violent shuddering?

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Often the cause of wheel shake on a 4x4, or in this case 6x6 is worn bearings in the swivel housings on the ends of the front axle, these bearings have to be tightened to a determined preload using shims so the swivel bearings are under pressure and offer resistance when moving the steering swivels, they have a damping effect, if they are worn and there is insufficient resistance then wheel shimmy can occur

 

Previous post about a GMC with same steering shake problem and new swivel bearings which cured the problem

http://hmvf.co.uk/forumvb/showthread.php?3453-GMC-Truck-Steering&p=35373#post35373

Agreed with Nick about swivel pin preload.

 

To assess this, jack up the front of the truck and disconnect the drag link and both ends of the track rod. Then swivel the wheels back and forth to see how freely they move.

 

- MG

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Thanks All for your replies.

After examining your suggestion and isolating, The fault has been traced to a slightly warped wheel rim.

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Pleased you've got it sorted

the GM box is one of the better wartime steering systems and usually performs well providing all the bits hanging off it are in good shape

Pete

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If I am right in my thoughts, when the civilian GMC's were designed they had a new revolutionary steering box design, the re-circulating ball system. Much much better than the older type of worm and peg. When you think that the size and weight of the GMC's and once they are moving you are able to steer them with one finger thats quite a feat.

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If I am right in my thoughts, when the civilian GMC's were designed they had a new revolutionary steering box design, the re-circulating ball system. Much much better than the older type of worm and peg. When you think that the size and weight of the GMC's and once they are moving you are able to steer them with one finger that quite a feat.

 

That's right Cubed, it was a GM design feature found on GMC and US and Canadian Chevrolet, it never fails to surprise me just how light the steering is even with a winch hanging off the front. There is no comparison in performance and handling of a recirculating ball box vs worm and peg or even worse worm and nut, the experience of having to drive a Morris CS8 for a number of miles still haunts me nearly 30 years later :drive:

 

Pete

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