dcfluid

I have word from my Ford source looking into my 0 to 30 kph acceleration shudder while towing with my Ecoscrew 6.5 box FX4.
Ford Canada had been trying various solutions on a dyno and has actual video of the problem while it happens.
In this particular shudder problem (unrelated to deceleration shudders or hard shifts) when the torque is applied to the axle the rear leaf springs deflect at the front mounts allowing the axle to twist enough to bind the u joints .
This is commonly know as spring wrap. Common with high horepower and muscle cars. It is why some vehicles need traction bars or similar device.
Ford is working on a fix but nothing yet that doesn't affect ride to their satisfaction.
I'm at the top of the list for guinea pig to test a fix.
I'm also thinking of machining up a traction bar device patterned after a Caltrac design that doesn't affect ride quality and attacks the problem right at the source. Ford will reimburse my costs to try it out.

So Ford knows the problem and is trying to find a solution that works for them. Probably needs to be cost effective for them to consider it as well.

My truck goes in for service next week and I'm getting a transmission reflash and driveshaft spline lube to help with other issues.
I'll post updates as they come.

I started a new thread because this acceleration shudder is spread around in 3 other threads discussing transmission problems.

EricTheOracle

I explained to my service writer that it felt like the leafs were winding up and then stated the problem can be from one of three things. binding driveline, pinion angle (again a binding problem) or the springs.

dcfluid

We've know for some time it was torque induced driveline binding. Ford pinpointed the exact spot. The front of the springs bowing up. A double wrapped spring at the front would do it. So would my Caltrac bar idea.
It will be interesting to see what fix they do come up with.

HogFan

Gonna ask a stupid question here, I see that both of you have the 6.5 ft box, will the same apply to the shorter 5.5 ft bed. I would assume so, but was not sure if the longer bed had a different rear spring set up?

dcfluid

My understanding was that it was mostly 6.5 box Screws with 2 piece driveshafts that displays this problem the most. It has to do with the driveshaft angle being different.
However Ford has tried changing driveshaft angles in several different ways with no results.
I would think an Ecoscrew 5.5 box would have the potential to wrap the springs too. Perhaps the angle is just so different.

Skandocious

This issue is more commonly known as "axle wrap."

You see it even more on trucks with large lift blocks (larger moment arm torquing on the axle) and/or small/soft spring packs. The best way to reduce axle wrap is just like you said-- using trac bars. You can sometimes also remedy axle wrap with overload springs or by replacing large blocks with lift springs, add-a-leaf's, etc.

Good luck with getting it fixed-- shouldn't be too hard. The hardest part is figuring out where it comes from, so you're past that

mello_collins

I wonder if a Roadmaster Active Suspension would help?

Merlyn

Interesting... I have experienced the same type of problem while towing our travel trailer with my truck. Just like above, it only occurs from 0 - 35 mph or so. I will have to mention this when I go in for my next oil change.




2011 F150 5.0 SCrew 6.5 Bed FX4

rocco

i had the same problem, Airbags fixed that. Might be something that ford has to consider making a factory piece.

Ford850

dcfluid,
You should see if Ford would reimburse you for a set of SuperSprings. They might solve it, plus you get the benefit of a level rear when loaded or towing.