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Definitive Discussion: Let's talk about Axle Wrap

Discussion in 'The Garage' started by zakk, Jan 29, 2003.

  1. zakk

    zakk 1/2 ton status

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    Definitive Discussion: Let\'s talk about Axle Wrap

    OK, with all this axle wrap stuff floating around let's have the difinitive discussion on the subject.

    My understanding is too basic, so let's have a few of the resident expert answer some questions. for example:

    1) what is axle wrap?

    2) what causes it?

    3) what does it break?

    4) how do we fix it?

    5) how can we tell we have it?


    The idea is to have a archive-able type post for future reference.

    Game on!
     
  2. zcarczar

    zcarczar 1/2 ton status

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    Re: Definitive Discussion: Let\'s talk about Axle Wrap

    1) Axle wrap or spring wrap is when the pinion tips up from the torque of the engine trying to rotate the tires. Lift blocks cause a lot of axle wrap because they increase the leverage of the housing on the springs.

    2) Engine torque, soft springs, lift blocks, big tires, a lot of traction

    3) U joint, Driveshafts

    4) With an A-Tron anti-wrap bar.

    5) If you have wheel hop or you have someone watch your pinion as you power brake it to see if the pinion tips upward a lot.

    Hope that helps. /forums/images/graemlins/thumb.gif
     
  3. heavy4x4

    heavy4x4 1/2 ton status

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    Re: Definitive Discussion: Let\'s talk about Axle Wrap

    I by no means consider myself to be one of the "resident experts," but I know my stuff, and if I don't, I'm content to say, "I have no idea." Read on:

    </font><blockquote><font class="small">In reply to:</font><hr />
    1) what is axle wrap?

    [/ QUOTE ]
    Axle wrap is the result of the springs twisting themselves into an "S" shape when the engine puts a load to the axle...for example, accelerating from a stop. Picture the normal rear spring. Now, under load - if you have axlewrap - it will look like "~"

    </font><blockquote><font class="small">In reply to:</font><hr />
    2) what causes it?

    [/ QUOTE ]
    The torque transferred to the axle - then multiplied in the diff sideways to the axleshafts - creates a great amount of up-and-down force on the axle housing, forcing the pinion to waver up and down. This is a result of the tires making great contact with the road - and then when power is applied, the tires drive the pinion/axlehousing in an upwards motion before the vehicle gets moving. What helps cause axlewrap....strong power and weak springs.

    </font><blockquote><font class="small">In reply to:</font><hr />
    3) what does it break?

    [/ QUOTE ]
    Axlewrap is very hard on u-joints particularily. As these joints are spinning, the axle is forcing them to operate at varying angles. This leads to premature breakage.

    </font><blockquote><font class="small">In reply to:</font><hr />
    4) how do we fix it?

    [/ QUOTE ]
    Several things can be done. One, get stiffer springs. Two, get traction bars/anti-wrap bars (offered by A-tron). Three, there are traction lifts which are bars that mount between the spring pack and spring perch...these then continue outward and are connected to the spring closer to the front shackle via a pivoting assembly. Not the best route, but it works...as the axle is forced upward, the connection to the spring keeps it from spinning to much.

    </font><blockquote><font class="small">In reply to:</font><hr />
    5) how can we tell we have it?

    [/ QUOTE ]
    With axlewrap, especially severe cases, there is a noticeable bounce upon acceleration. This is the result of the spring finally springing the axle back down to the proper placement, with the tires still driving, which forces the whole rearend up.

    There, hope that helps out.
     
  4. BigOrange90Jimmy

    BigOrange90Jimmy 1/2 ton status Premium Member

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    Re: Definitive Discussion: Let\'s talk about Axle Wrap

    </font><blockquote><font class="small">In reply to:</font><hr />
    1) what is axle wrap?

    [/ QUOTE ]

    It is the springs creating an S-shape from the housing rotating upwards. Major side effect is wheelhop.

    </font><blockquote><font class="small">In reply to:</font><hr />
    2) what causes it?

    [/ QUOTE ]

    It is caused by the torque from the engine being transferred to the ground by the tires.

    </font><blockquote><font class="small">In reply to:</font><hr />
    3) what does it break?

    [/ QUOTE ]

    It can break U-joints, leaf springs, traction bar mounts, axle shafts (from excessive wheelhop), ring &amp; pinion, carrier, bend spring mounts, shock mounts.

    </font><blockquote><font class="small">In reply to:</font><hr />
    4) how do we fix it?

    [/ QUOTE ]

    Add a traction bar type setup, ranging from a single link setup from the center of the differential or up to even a 4 link setup. Ladder bars and traction lift blocks can be used as well. Kicker shocks or stiffer springs work also.

    </font><blockquote><font class="small">In reply to:</font><hr />
    5) how can we tell we have it?


    [/ QUOTE ]

    In most cases, wheelhop under hard acceleration.


    Hope this helps a little.
     
  5. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Re: Definitive Discussion: Let\'s talk about Axle Wrap

    Looks like anything I would add has been said. BTW, the principal problem with my rig eating rear springs is due to axle wrap. Luckily, I've had no u-joint breakage, nor have I had wheel hop, but you can sure see the axle rotating while braking or accelerating (particularly climbing).
     
  6. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: Definitive Discussion: Let\'s talk about Axle Wrap

    The worst axle wrap I had was during a panic stop with the huge one ton rear brakes. As the rear tires locked the pinion dived and started a vicious cycle. The pinion would dive because the springs are so soft...eventually the springs overcome the pinion dive and snap the pinion back to where it normally is. Eventually this got violent enough the the rear tires began to hop and bounce...IMO very dangerous! I almost hit what I was trying to avoid hitting because of this.

    The anti-wrap bar triangulates the housing of the rear diff so the pinion cannot rise or dive.

    The difficulty in anti-wrap design is three major factors come into play. It must stop the axle wrap, there are some bars out there that don't make it past this critical step. Secondly we don't want to inhibit suspension movement or flex. Some bars stop the axle wrap at the expense of flex. Thirdly we want to keep anti-squat sane. Jeep Wranglers are known for horrible anti-squat when lifted...the rear lifts under power (like a climb...)

    The anti wrap bar will save drivelines, U-joints and springs from premature failure.

    I know this isn't the A-tron post, but you can see there is some justification for spending the dollars in this area of the truck. Drivelines and springs can also add up quickly if you have bad axle wrap.

    Rene
     
  7. Skigirl

    Skigirl 1/2 ton status

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    Re: Definitive Discussion: Let\'s talk about Axle Wrap

    Could you explain what wheel hop is, how it feels, what happens, etc.?
     
  8. zcarczar

    zcarczar 1/2 ton status

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    Re: Definitive Discussion: Let\'s talk about Axle Wrap

    Its when the wheel is actually hopping up and down, you will know when you get it because the rear of the truck will be bouncing like crazy and making wierd and awful noises.
     
  9. Skigirl

    Skigirl 1/2 ton status

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    Re: Definitive Discussion: Let\'s talk about Axle Wrap

    Thank you. /forums/images/graemlins/thumb.gif
     
  10. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: Definitive Discussion: Let\'s talk about Axle Wrap

    Feels like a jack hammer is loose under the truck...it's a pretty unmistakable feeling.

    Rene
     
  11. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    Re: Definitive Discussion: Let\'s talk about Axle Wrap

    Even in less severe cases (no jackhammer feel) it can be damaging, like Russ said, it's a big killer of leaf springs since you can wrap the springs to the damaging point without breaking traction. Worst case scenario is a steep climb with the rear articulated. The leaf spring at full compression with a lot of traction is going to deform and overstress.

    Best way to get an idea of if you have it and what it looks like is to watch the truck in a high traction climb, or even a brisk takeoff on pavement. You'll see the pinion action and it becomes very obvious.

    Heavier axles and tire will make it worse since you have more weight cyling when it all hops.

    I've also run into situations where changing tires changed the wrap problems. On a Moab trip one time I drove a sand road to a campsite on my street tires, swapped on the swampers and drove out. On the skinnyxbaldR16's I had the jackhammer effect when I got on it in the sand, with the swamps, nothing but go when I stomped it in the sand. Basically the swampers were hooking up and staying hooked up where the baldies would push a bit and turn loose, starting the hop cycle.
     
  12. wayne

    wayne 3/4 ton status

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    Re: Definitive Discussion: Let\'s talk about Axle Wrap

    The worst I've had happen was it took the t case output shaft and housing out. /forums/images/graemlins/tongue.gif Didn't do anything to the driveshaft or u-joints. I have also seen axle wrap on a vehicle running blocks in the back and it was that bad it broke the blocks and spit them out the back of the truck.
     
  13. big pappa b

    big pappa b 3/4 ton status

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    Re: Definitive Discussion: Let\'s talk about Axle Wrap

    Here's a link to a good article about axle wrap:

    Axle Wrap
     
  14. BorregoK5

    BorregoK5 1/2 ton status

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    Re: Definitive Discussion: Let\'s talk about Axle Wrap

    Quick visual reference - The left side top is at rest, the left side bottom is wrapping up under load-

    [​IMG]

    The wrap can be hard to feel until it unloads (loss of traction or shift of gears) and the pinion snaps back down.
     
  15. hardcore_rob

    hardcore_rob 1/2 ton status

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  16. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    Re: Definitive Discussion: Let\'s talk about Axle Wrap

    Wheelhop (as stated) is not good for u-joints, driveshafts, and suspension components, but it is also tough on axles and differentials. Bigger meats and/or bigger motors make it worse, especially with lighter duty axles. Axle shafts can fatigue and snap or twist splines, carriers can crack or fatigue. The worst part is they usually totally crap out when driving to the grocery store and not during abuse, but it was the previous abuse that lead to it.

    As the my username implies, I am very heavy on the skinny pedal. I use kicker shocks (which I believe only help marginally), but the biggest improvement to stopping my wheel-hop was taking out the 4" blocks I had and replacing the springs with a slighter higher rated 4" arched spring pack.

    With mucho power under the hood, locked 14FF, and 33" street tires (can't seem to stomach roasting the larger ones....$$$$$), I can put on a sweet smoke show with virtually no hop. Whereas before, it would rattle the fillings out of your teeth, and I'm sure wasn't good for the drivetrain.

    This is in a fullsize pickup designed for truck pulls so I can get away (and actually desire) a stiffer suspension, but for a trail-rig (or even an on-road/off-road rig), I would definitely consider A-trons anti-wrap bar. After hearing testimonials and looking at pics, it may be a few coins to buy, but in the end it's cheap insurance and won't limit articulation or flex.
     
  17. Twiz

    Twiz 1/2 ton status

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    Re: Definitive Discussion: Let\'s talk about Axle Wrap

    4) how do we fix it?

    Several options avalible,
    Something I haven't seen mentioned in-awhile. Stiffing up the front of the leaf spring pack.
    Drag-raceing "sleepers" would attemp to make thier cars look as bone-stock as possible, no ladder-bars, no traction enhancing gimmicks, nothing that could be "seen". What they did was stiffen up the front half of the spring-pack, by useing "half-leafs". Meaning, the front section of the leaf-spring might have 3 or 4 leafs in the pack, while the rear section might only have 2. This kept the spring from wraping and helped prevent wheel-hop. Some went so far as to clamp a half-pipe to the front section of the leaf spring.

    Carried over to something meaningful to us,
    It might be in our best intrest to keep the front section of the leaf-spring clamped tight or at-least kinda-tight. Doing so, will keep the front of the pack stiff and prevent it from wraping up, yet still allow the rear section to be free and flex as needed.

    Another item that is often over-looked is to keep the shocks staggered as they are stock.
    It doesn't matter wich one is in front of the axle and which is behind, just as long as they are not on the same side.
    Probably the most famous example of the staggered shock system in use is the '68 camero.
    The '67s used a single leaf and a paried shock set-up, this system exprianced exsessive wheel-hop even under slight throttle in-put. (le' me tall ya' /forums/images/graemlins/grin.gif)
    In '68, Chevy reengineered the rear suspension and used a 3-leaf pack with stagered shocks. End result, far-less wheel-hop than before.

    Just some thoghts to keep the ol' gray matter active.
     
  18. ZonkRat

    ZonkRat 1/2 ton status

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    Re: Definitive Discussion: Let\'s talk about Axle Wrap

    Bringing this back to front for other post. /forums/images/graemlins/thumb.gif
     
  19. blueturd

    blueturd Registered Member

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    Re: Definitive Discussion: Let\'s talk about Axle Wrap

    Ur, my 68 camaro had mono leafs, where in the hell did the three come from? I thought only SS, RS, and Z28 had multi leafs. Much confused! /forums/images/graemlins/usaflag.gif
     
  20. ChevyCaGal

    ChevyCaGal 3/4 ton status

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    Re: Definitive Discussion: Let\'s talk about Axle Wrap

    Rene, the A-Tron axle wrap bar you installed, what have you noitced as far as it afecting things like flex and such. I finally decided to go with the 57" springs in the rear for flex, but will this change things for me, or really anyone who installs one?
     

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