Axle Wrap ?s
 

I tow a 12k 5th wheel with my 2010 250 with 3.55 gears. Ill be installing airbags after xmas (please wifey.) Ive heard airbags can worsen the effect of axle wrap. Is that true? I do have some shake under acceleration from a stop and Ive been told that axle wrap from the torque being applied to the ground when towing a large load. Any truth to this and would ladder bars help? Im planning a trip out west from Mi doing about 2k mi each way this spring. I want my truck set up in the best possible way. Without buying a f 550 what can I do to make my truck ride smoother.
Thanks
STM

I believe this shudder or vibration is due to the angle of the driveline when loaded. Consider the amount you are lowering the rear when you hook up that 5er.

Now add in all the torgue and it will do that vibration and shudder when getting on it. Mostly at the lower speeds under a hard acceleration.

Air bags will help with this by bring your truck back up to level. Airbags will also help with your suspension by absorbing some of the dips in the road as you move along.

I can watch my air guages go up and down with the road as i am traveling. It also will help to keep you from hitting the bumpstops if you go thru a pothole or something.

So I am sure there is a big of axle wrap as well but don't think that is your symptoms.

Thanks Senix,
Ive learned a lot from you since getting this 5th wheel. Makes sense about the angle. Can you get your truck back to level (stock looking) with the airbags? My wife will be ordering them for me for the holiday. Part number 2450. Is that what you have. Also I was going to run the lines to the rear of my truck and install a t fitting so both bags fill up together with the same psi at once. How does that sound to you? One more thing!
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This the 1230volt compressor I want to use do you think it will be adequate?
Sorry for all the questions. This whole thing is new to me.
STM

STM,

I am sure others will have some input as well. I can get mine to level very easy. I have them set at 5 psi emtpy, hook up and adjust as needed. I raise mine just enough that the lowest leaf spring has just a little left before is would completely join the rest of the pack...if that makes sense. Seems to ride great there for me.

2450 is what I have as well. I also have a 1gal onboard tank and compressor. I have dual guages for mine.

That compressor should be more than enough to air them up. I think 100 psi is max for each bag and you won't need near that. maybe 30 psi in each is my bet.

I have been using 5000lbs air bags with a on board compressor for years, I run ours at 55 to 60psi with our trailers 3200 to 3400lbs pin weight. Truck rides level and it makes for a superior ride over stock, I'm also running Monroe Gas Magnum shocks to help with rebounding on rough roads. If you are having shake under acceleration it may not be axle wrap but the limited slip rear end unloading. I would try a tube of friction modifier and see what happens. I changed my gear grease last year and had to add another tube just the other day to stop my limited slip from jumping on take off under load. It's the same thing that happened when the truck was new 10 years ago.

Denny

I dont think that your having problems with axle wrap. Axle wrap much more often accompanies lift blocks and the extra torque applied when your in low range, as well as large tires. However, you cant go wrong with ladder bars. They will improve the feel of acceleration and get rid of the small amount of axle wrap thats always present.

If you do decide to get ladder bars, make sure you get ones that have the shackle at the frame end. because as the spring compresses and decompresses the axle move forward and back, and you dont have a shackle there, then it will bind and cause problems. Most cars dont have to worry because they dont have near the travel of trucks and dont carry differing loads.

There is a TSB addressing this issue # "09-20-5 shudder or vibration on acceleration - especially loaded". The info is up the top under Full Text TSBs.

It's caused by too much "sag" in the rear end, when loaded, which ends up changing the operating angle of the drive shaft resulting in a vibration on take-off.

I have the same problem and, like you, plan on installing air-bags in the spring to keep the truck in it's unloaded height when the 5th wheel is hooked up.

Okay guys, what the heck is axle wrap? Never heard of it. Is it a fifth wheel thing?

I don't think you want to tie the two sides together with a tee fitting. You want each bag to be independent of the other. If you use a tee fitting to air them both up at the same time it allows the air to flow back and forth between the bags when going around corners and such allowing the truck to lean, i.e. the air flows to the air bag on the side of the truck with lower load.

Best way to describe it as the amount of movement in the rear axle, pinion and stuff, leaf springs when you put power to the driveline.

Never thought of that but makes total sense. Ill just route both airlines to the rear of truck and air each bag separately to needed psi. I cant imagine those bags take too long to air up. Anyway Ill be very curious to see the differences having the truck leveled makes in reducing vibrations.
Thanks for all the help above.
STM

Axle wrap is where the leaf springs allow the axle housing to turn a bit due to the torque being applied. When unloaded, it becomes wheel hop, but when the wheels can't lose traction, it can get bad enough to damage universals, and even the driveshaft itself.
The softer a leaf spring rides, the worse this can get, since the spring flex is what does it.

It's very common in drag racing not so much in pulling loads but it can happen. If it's happening to the OP then air bags will probable stop it by changing the pinion angle under load. If not and he has a LS rear end I would suggest adding friction modifier to solve the problem before he spends a lot of money solving a simple problem.

Denny

Everybody has explained this very well but while I was surfing the web a few minutes ago, I found this diagram of axle wrap. Basically, it's when torque / power is applied and the axle begins to "wrap" in the leaves as shown in the diagram:


http://www.axlewrap.activesuspension...s/Axilwrap.jpg

Hope this helps fz1dave.

Thanks powerstroke72. A picture says a thousand words. :)

Hopefully I'll never have that problem.