Rear End Binding Up When Slowing Down or Taking Off Slow

[SOCOMech]

SOCO,
I have to disagree with this. Has absolutely nothing to do with weight distribution. Wheel hop is caused by the pinion angle changing under acceleration.

Yes, pinion angle change will cause it but, the suspension loading and unloading is affecting the pinion angle.......and weight over the suspension will affect it's manners. If you take a Raptor as is and put it in the sand, wheel hop can be very pronounced, take the ame truck and put some decent weight in the bed and it will reduce the wheel hop. We're both agreeing on what causes it but weight over the axle will most deff. have an affect on it.

 

[JP7]

I think the simple answer Leadfoot - is stiffer springs reduce wrap. Loose springs, give you more play when flexing the truck (either slow or fast) - but the sacrifice is the increased movement of the rear end when loaded up with torque from the driveshaft.

With the HP in the Raptor, combined with gearing, the shaft wants to turn that axle sideways and spit it out every time you mash the gas pedal. Mild axle wrap can actually be of some use offroad when in mud (more on that when I have time) but it's definately not a good feeling on hard ground or pavement.

 

[BIRDMAN]

Bird,
The hop is caused by the loading and unloading of the suspension. The load/unload is caused by the movement of the pinion. Does not matter if it's a car or truck. If a vehicle has wheel hop the axle housing is rotating. It gets a little more complex if the vehicle has an IRS. For a solid axle vehicle if you have wheel hop a traction bar or linked suspension will cure the hop.

On the Raptor issue I am speculating what I believe the problem is as I don't own one yet. On the wheel hop/axle wrap issue that is 30+ years of racing and race car fabrication experience.

i'm not sure we're on the same page here but i'll take your word for it...

 

[BIRDMAN]

"Good times....... Noodle salad."

Where do they teach you to talk like this? In some Panama City "Sailor wanna hump-hump" bar, or is it getaway day and your last shot at his whiskey? Sell crazy someplace else, we're all stocked up here.

 

[JP7]

i'm not sure we're on the same page here but i'll take your word for it...

Lol I noticed there was a few pages in this book. But after a few more miles, I'm pretty sure my issue isn't wrap as much as bind - I'll check it out with the dealer next week when I have more time.

 

[warrior]

had mine at the dealer yesterday for the same problem, tech rode with me for 30 secs, "lube the slip yolk", took driveshaft off, lube and presto NO clunk/bump/wrap.

 

[Hockster]

I think the simple answer Leadfoot - is stiffer springs reduce wrap. Loose springs, give you more play when flexing the truck (either slow or fast) - but the sacrifice is the increased movement of the rear end when loaded up with torque from the driveshaft.

With the HP in the Raptor, combined with gearing, the shaft wants to turn that axle sideways and spit it out every time you mash the gas pedal. Mild axle wrap can actually be of some use offroad when in mud (more on that when I have time) but it's definately not a good feeling on hard ground or pavement.

You should include the rubber durometer.... If you changed all the rubber in the system you will reduce this problem but it sacrifices ride quality...

 

[kglesq]

Problem Solved . . .

Just picked up the truck after they lubed the slip-yoke. It cured the problem 100%. So significant is the improvement it's like a different truck. Service advisor mentioned that he has seen more than a few trucks coming in with this problem.

So while the Raptor may well suffer axle wrap, that is NOT what is causing this problem. Which is good news, as it means the problem is easily solved, and a warranty item.

More here: http://www.fordraptorforum.com/f5/25-days-later-1314/#post18231

 

[Droid]

Just found this on some other site whose name cannot be heard...apparently Ford issued an SSM on it:

21712 2011 Raptor Driveline Clunk/Slip/Bump/Chirp
Some 2011 F-150 Raptor Vehicle built on or before 1/7/2011 may exhibit excessive clunk or a chirp/slip/bump condition from the driveshaft on acceleration from a stop or when bringing the vehicle to a stop. This condition typically occurs on vehicles with less than 2000 miles. This condition is currently being investigated by engineering. In the interim, lubricate the driveshaft slip yoke at the transfer case using Motorcraft PTFE lubricant... Continue to monitor for updates.

 

[JP7]

Mine goes in tomorrow to have it done. While the sales guy Cam is great to deal with - the mechanics (only SVT shop in town) are not amenable to taking advice from customers so I'll show them this thread