Ok, all you pros, I need some help.. I was out at Glamis this weekend, and saw some MONSTER trucks.. I have a 2001 F350 CrewCab diesel, with a 12" Truck toys lift.. it has 4" hangers, with an actual 8" suspension lift, with FabTech leaf springs. I also have the 4" blocks in the back. My problem is this: On take off, the truck vibrates, due to the angle of the driveline, and what the shop told me was refered to as "axle wrap" The shop manager there told me that the "axle wrap" will not hurt anything, its just the axle meeting the angle of the driveline. Is this true? I sure hate feeling the vibration on a brand new truck and want to get it remedied as soon as possible, sooner if I run the risk of screwing up the gears or something else. I will eventually switch the rear blocks out for a Nat'l spring leaf 12" leaf kit, and add traction bars, but I heard the best way to eliminat the axle wrap is to reposition the shock mounts on the axle, and meet the angle of the driveline. Is this the only option, or has someone heard of doing something different? If so, any shops in California that do the work? Everyones help is greatly appreciated, as I hope to get this fixed.. Thanks!!

-Ry
2001 Monster F350 CrewCab 4X4 7.3 PowerStroke, Bright Amber Metallic, 12" lift, 39" Mickey Thompsons on Weld Typhoons..

 

There are a few things you can do to eliminate axle wrap. First off, axle wrap is what happens on takeoff, and stopping. The torque created when you put power through the tires and onto the ground causes the springs to bend in an S, which changes the driveshaft length. This also happens when stopping. Your lift blocks are only adding leverage against the springs, so the sooner you replace the blocks, or stop the axle wrap the better. Severe axle wrap will tear up a u-joint, and could destroy a drive line as well. (Under severe conditions)

One option you have to reduce the axle wrap is to move the shocks. However, this doesn't help a lot. I am not sure about the new Fords, but my 82 has both shocks in front of the axle housing, pointing forwards. The 70's Chevy's had a design where one shock pointed forward, and the other faced rearward. This helped reduce axle wrap, but not eliminate it.
Another option is to put ladder bars on it, but this could be costly, and since they mount things solid, dune running it could break things (such as mounts, bars, housings, etc).
Rancho makes a kit to help reduce wrap called kicker shocks (I think). This kit comes with mounts and 2 shocks. One mount is welded (or bolted) to the frame just behind the front spring hanger (on the rear of the truck), and the other is bolted to the u-bolt plate over the housing. A shock is placed between the mount and the u-bolt plate. When the axle twists, the shocks help dampen the wrap. This seems to work pretty well.
I welded a bracket on top of my rear pumpkin which sticks up about 6". I also welded in a bracket to my crossmember under the bed. I then installed a shock between the two, and my wrap is not as noticable. The shock works because you can see where the dirt have been worn off about 2" up the piston rod.
Another option to look into is a special bar that is built specifically to eliminate axle wrap. It is the same idea as a ladder bar, except it is not mounted solid. This mounts to the housing like a ladder bar would, but at the other end of the bar, there is a shackle that mounts to the frame. This keeps the housing from rotating but still allows it to flex side to side, and up and down.

Sorry for the book, but I hope this helps.

Chris
cmercer@auxserv1.unco.edu
http://www.mountaineers4x4.org/mercer
'82 F-350, '53 Dodge PU, '85 4Runner
Proud enough to stack hay, crazy enough to eat it.

 

No, the book is fine, I appreciate the time.. I will have to explore a few options, and scout out some places that are capable of doing the work here in California. Just to clarify however, under normal conditions, the axle wrap should not affect anything other than a little vibration.. Every time I feel it I cringe that something it just waiting to grenade..

-Ry
2001 Monster F350 CrewCab 4X4 7.3 PowerStroke, Bright Amber Metallic, 12" lift, 39" Mickey Thompsons on Weld Typhoons..

 

If you are just driving on the pavement, not towing anything, and son't take it off-road, then you are fine. However, I am sure that since you have put the time, money, and work into your truck, I am sure you are going to use it. If you were to stand on it off of a light, and the tires start spinning, when they stop spinning and aquire traction, it is going to wrap the axle. This can cause the springs to wrap, which rotates the 3rd member, which very well could explode a u-joint or bind and twist a driveshaft.

I'd try to eliminate (or at least reduce) it as soon as possible.

Chris
cmercer@auxserv1.unco.edu
http://www.mountaineers4x4.org/mercer
'82 F-350, '53 Dodge PU, '85 4Runner
Proud enough to stack hay, crazy enough to eat it.

 

Let me describe what I think axle wrap is, and have you flame me about how wrong it is, heh.

Ok, when I rev it up to 2k RPM, drop clutch and go in straight line, the tires spin for about 15 feet, then truck starts to buck, bounce and shudder, but if I do the same thing and turn hard left or right truck doesn't bounce at all and does donuts till I take foot off the gas...is that bouncing because of axle wrap??

1995 F150XL - Reg cab/bed, 4.9L, 5-speed, Metallic Navy Blue/Gray int.
Mods: Tanno cover, bed liner, 1200 watt amp, 2 10" Rockford Punch Subs, sony cd, K&N Filter, Flowmaster 40 series (no visible exhaust exit) BFG A/T 31"x10.5"R15 & Rancho RS5000 shocks

 

the bucking and bouncing could be your differential seeking traction as tires break loose under acceleration. do you have locking differentials? this could also explain why turning left and right eliminates the bucking because you are loading the axle as you turn and this causes differential to change amount of power to one sideto prevent tire wear.
if you have ever driven a posi-traction rear you might have felt the effect of the lack of different rotating speeds of tires when turning. they squeel real nice!

 

I'm pretty sure I dont have locking diffs, but I do leave marks like I have posi. The door code says I have axle 12, which is a 2.73 rear end, but the truck also has the tow package, which is usually 3.55's, LoL I have no idea, but 75 mph on freeway is 1800 RPM


1995 F150XL - Reg cab/bed, 4.9L, 5-speed, Metallic Navy Blue/Gray int.
Mods: Topdeck bed lid, protecta bed liner, 1200 watt amp, 2 10" Rockford Punch Subs, sony cd-player, K&N Filtercharger, Flowmaster 40 series + custom exhaust (no visible exhaust exit) BFG A/T 31"x10.5"R15 & Rancho RS5000 shocks

 

Yes, the bouncing is the springs wrapping. You may also notice a shuddering feeling while taking off from a light, or stopping for one. I notice it on my truck mostly when I am in the snow. When the tires are spinning, there is no stress on the springs. But when the tires gain traction, they no longer spin. However, since there is a lot of momentum from the tires spinning, when they gain traction, the momentum is transfered into the axle housing, which will twist and wrap the springs.
As for why it does it while going straight, but not when turning, the axle still wraps, but when you are doing donuts, the tires are continuously spinning. If you were to spin a few donuts, then drive straight out of it, you would notice the bouncing when the tires gained traction again.

Chris
cmercer@auxserv1.unco.edu
http://www.mountaineers4x4.org/mercer
'82 F-350, '53 Dodge PU, '85 4Runner
Proud enough to stack hay, crazy enough to eat it.

 

An easy way to cure axle wrap is with an axle wrap bar. Get 2 male end heim joints and the screw in cap and weld it into a 1" id black wall tubing. The make a bracket and weld it onto the top of your axle housing and the frame crossmember. Then bolt it in. This will eliminate the wrap and allow the rear end to twist up.

 

 

That last option you was talking about being similar to the ladder bar, what is it exactly?

 

Welcome to FTE.

Tagging on to 19 year old threads won't get you a lot of answers. None of these guys have been on the sight for years.

Ladder bar:

https://www.jegs.com/i/JEGS/555/64672/10002/-1