Axle wrap?
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Joined: Dec 2008
Posts: 49
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From: Alaska
I would say it's definitely axle-wrap.
I noticed this on my truck since new.
Soft leaf springs.... well... good load carrying capacity in the verticle plane... but compared to the old days, they are LONG for ride quality. Such long springs are easy to twist... "easier" anyway.
No offense, but no one who posted in here really nailed what axle wrap is.
Axle wrap is all about twisting forces (torque).
As the driveline twists it's 'driving' the pinion gear against the ring gear. That 90 degree change in direction of twisting force means the tires get turned.
But wait, the tires need resistence... not from the road, but from some counter-acting force on the truck.
That first component is the leaf-spring. The leaf spring(s) "locate" the axle housing... meaning they position the axle housing and hold it in place.
In addition to "locating" the axle housing, the leaf spring is providing more or less a vertical movement of the axle.
But when quick bursts of torque are applied, the tires grab traction and the twisting force of the axles wants to propel the truck, right?
First, the "torque" (twisting force) must be arrested and controlled to provide forward motion. It's the job of the leaf springs to do this.
Eventually the leaf springs arrest the twisting force of the axles and tires and transfer that torque into the frame and propel the vehicle forward.
But in arresting the force, it give somewhat... "WRAPPING" in a weak "S" shape before the strength of the spring overcomes the weight of the vehicle.
You feel this on pavement by going from a stop or slow speed to stepping on the gas. The truck will lurch, or jump, or squat momentarily. Then it relaxes and you're on your way.
Ultimately, the drive shaft pinion gear is trying to twist the ring gear, but due to wheel resistance (traction) the drive shaft momentarily "rides up" the ring gear. This appears as though the pumpkin (differential) rotates upward under applied torque (or power).
Imagine you are holding a powerful portable drill in your hands as you prepare to drill into a piece of metal with a 3/4" bit. There's going to be resistance at first. If you're a big tough guy you can counteract the torque (twisting force) at the beginning, right? I know I can.
The only solution to both "Axle-Wrap" and drilling a powerful drill with a large bit is to "brace off". Brace the drill against your leg or something.
On a truck, such companies of the like (Pro Comp) provide rear axle locator/torsion bars (whatever they like to call their product) on their lift kits to reduce or eliminate axle wrap. It mounts one end to the frame and the other to the low side of the axle so as to assist to take over the springs work of counter-acting twisting force.
This prevents your vehicle from jumping, loading up and relaxing which can really be felt and actually stresses varying components of the drive line system.
My aim is to go a mild lift or no lift but find a way to get some anti-axle-wrap bars for my truck so it rides better and stresses out the truck less.
I noticed this on my truck since new.
Soft leaf springs.... well... good load carrying capacity in the verticle plane... but compared to the old days, they are LONG for ride quality. Such long springs are easy to twist... "easier" anyway.
No offense, but no one who posted in here really nailed what axle wrap is.
Axle wrap is all about twisting forces (torque).
As the driveline twists it's 'driving' the pinion gear against the ring gear. That 90 degree change in direction of twisting force means the tires get turned.
But wait, the tires need resistence... not from the road, but from some counter-acting force on the truck.
That first component is the leaf-spring. The leaf spring(s) "locate" the axle housing... meaning they position the axle housing and hold it in place.
In addition to "locating" the axle housing, the leaf spring is providing more or less a vertical movement of the axle.
But when quick bursts of torque are applied, the tires grab traction and the twisting force of the axles wants to propel the truck, right?
First, the "torque" (twisting force) must be arrested and controlled to provide forward motion. It's the job of the leaf springs to do this.
Eventually the leaf springs arrest the twisting force of the axles and tires and transfer that torque into the frame and propel the vehicle forward.
But in arresting the force, it give somewhat... "WRAPPING" in a weak "S" shape before the strength of the spring overcomes the weight of the vehicle.
You feel this on pavement by going from a stop or slow speed to stepping on the gas. The truck will lurch, or jump, or squat momentarily. Then it relaxes and you're on your way.
Ultimately, the drive shaft pinion gear is trying to twist the ring gear, but due to wheel resistance (traction) the drive shaft momentarily "rides up" the ring gear. This appears as though the pumpkin (differential) rotates upward under applied torque (or power).
Imagine you are holding a powerful portable drill in your hands as you prepare to drill into a piece of metal with a 3/4" bit. There's going to be resistance at first. If you're a big tough guy you can counteract the torque (twisting force) at the beginning, right? I know I can.
The only solution to both "Axle-Wrap" and drilling a powerful drill with a large bit is to "brace off". Brace the drill against your leg or something.
On a truck, such companies of the like (Pro Comp) provide rear axle locator/torsion bars (whatever they like to call their product) on their lift kits to reduce or eliminate axle wrap. It mounts one end to the frame and the other to the low side of the axle so as to assist to take over the springs work of counter-acting twisting force.
This prevents your vehicle from jumping, loading up and relaxing which can really be felt and actually stresses varying components of the drive line system.
My aim is to go a mild lift or no lift but find a way to get some anti-axle-wrap bars for my truck so it rides better and stresses out the truck less.
I knew there was a reason I paid attention in physics
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Joined: Jan 2010
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From: Land of small dogs
Ok, now I am confused, is this happening only under acceleration or is this happening when you are driving on the freeway and hitting expansion gaps or both???
Here is what I want you to do and then report back. go find a place that your truck does this consistently. Do it with no load in the bed. Then put about 250lbs in the bed, toward the rear, something solid, not liquid, a fat friend will do (sorry I can't volunteer).
If you are getting this at consistent highway speeds, then it is more than likely not axle wrap and something to do with your shocks/springs or the fact that you are driving a truck and not a Cadillac. You have an XLT, what cab and bed setup, 2wd or 4wd?
Also, if you are not an aggressive driver (as in your post) then I find it highly unlikely that you are dealing with axle wrap. Some drag racers really do not have to deal with this until they hit 300+hp and are really hitting it at the track.
Here is what I want you to do and then report back. go find a place that your truck does this consistently. Do it with no load in the bed. Then put about 250lbs in the bed, toward the rear, something solid, not liquid, a fat friend will do (sorry I can't volunteer).
If you are getting this at consistent highway speeds, then it is more than likely not axle wrap and something to do with your shocks/springs or the fact that you are driving a truck and not a Cadillac. You have an XLT, what cab and bed setup, 2wd or 4wd?
Also, if you are not an aggressive driver (as in your post) then I find it highly unlikely that you are dealing with axle wrap. Some drag racers really do not have to deal with this until they hit 300+hp and are really hitting it at the track.