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Vehicle crabwalking?


PNWguy
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Was driving home tonight and was behind an early 70's Ford F100 2wd and I noticed that the rear wheels were offset about 4-6" from the front wheels.  I've noticed that phenomenon on a few old pickups over the years and always wondered what caused it.

Frame damage?  Messed up front end? 

Anyone have any idea?

Thought I'd find lots of pics on the internet of it, but no.  Here is an extreme example...

See the source image

Most examples I've seen over the years have been 4x4 pickups from the 70's.

 

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Broken or missing center bolts on the rear leaf springs are the usual culprit. Notice that the right side rear wheel is forward of the left wheel? That's because it's the 'torque-side' of the differential.

That wheel typically is the one that spins when you do a burn out - unless you've got traction control of some sort - either mechanical or electronic. This wheel also has the greatest thrust on it at that time, so the center(ing) bolt can fail there easier then the one on the left side.

Even 4-wheele driven vehicles aren't usually 'true-4-wd' in that the differentials are 'open' and not traction controlled. They still put most of the power out through the passenger's side of the rear end.

All things taken into consideration, it could be a broken spring hanger too - or Pinto springs on the right side.

 

BTW: we call it: "Dog Tracking".

Edited by JoeIsuzu
added thought.....
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7 hours ago, PNWguy said:

Was driving home tonight and was behind an early 70's Ford F100 2wd and I noticed that the rear wheels were offset about 4-6" from the front wheels.  I've noticed that phenomenon on a few old pickups over the years and always wondered what caused it.

Frame damage?  Messed up front end? 

Anyone have any idea?

Thought I'd find lots of pics on the internet of it, but no.  Here is an extreme example...

See the source image

Most examples I've seen over the years have been 4x4 pickups from the 70's.

 

Somethin's broke.

 

Could be lots of things but damage to the frame or the rear suspension is where I'd start.

I've seen less extreme examples where it appears that the rear end slipped on the leaf spring a little bit (ie wasn't mounted in the right place).

 

 

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Frame damage that wasn't repaired. What causes this is what is called a diamond. A diamond occurs when one frame rail is either pushed forward or rearward which causes the vehicle to dog track.

Truck frames are a ladder type construction. Imagine the results from pushing one side of of your extension ladder forward while leaving the the other side in place.

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8 hours ago, JoeIsuzu said:

Broken or missing center bolts on the rear leaf springs are the usual culprit. Notice that the right side rear wheel is forward of the left wheel? That's because it's the 'torque-side' of the differential.

That wheel typically is the one that spins when you do a burn out - unless you've got traction control of some sort - either mechanical or electronic. This wheel also has the greatest thrust on it at that time, so the center(ing) bolt can fail there easier then the one on the left side.

Even 4-wheele driven vehicles aren't usually 'true-4-wd' in that the differentials are 'open' and not traction controlled. They still put most of the power out through the passenger's side of the rear end.

All things taken into consideration, it could be a broken spring hanger too - or Pinto springs on the right side.

 

BTW: we call it: "Dog Tracking".

Yup. 

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We always did measurements of four points in the front and rear of damaged vehicles, to determine if they were "out of square" and if so, we continued to measure the vehicle to determine if it were in the running gear or body/frame structure.  It's simple to do, but sometimes the driver doesn't know.  And sometime the repairer doesn't care.

Watch when you follow someone. carefully center your view on where a trailer hitch would be located on the front vehicle, and see if you see equal amounts of front tires relative to the rear tires at the road.  Interesting to do.

Edited by janice6
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12 hours ago, PNWguy said:

Was driving home tonight and was behind an early 70's Ford F100 2wd and I noticed that the rear wheels were offset about 4-6" from the front wheels.  I've noticed that phenomenon on a few old pickups over the years and always wondered what caused it.

Frame damage?  Messed up front end? 

Anyone have any idea?

Thought I'd find lots of pics on the internet of it, but no.  Here is an extreme example...

See the source image

Most examples I've seen over the years have been 4x4 pickups from the 70's.

 

That is how my 03 Z71 drove after I was hit at a red light. It bent the frame behind the cab and pushed the driver side of the rear axle forward.  

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