I've got a post somewhere down in the list on my issues with truck hop at 49-50 mph if the truck is held at this constant speed for a continuous time (several minutes). The hop gets progressively worse. I've had the truck to three different shops. One shop did another road force (I believe the factory road force balances the tires). No change after any of the shops did their thing. I don't believe it is the Michelins. Hop is also bad at 75mph but that could be from everyone F'ing with the balancing. It's going to a specialist tomorrow or wednesday (a Ford dealer in Nashville that specializes in 3/4 ton and up trucks - they started asking me the right questions when I called them).

One of the shops mentioned the drive shaft (balance?). I thought I'd look at mine (knowing there is no way to tell anything from eyeballing it). This photo is the drive shaft coming out of the transmission housing. It has some oil splatter on the bottom of the truck from the shaft spinning and the oilywear pattern on the shaft appears to make it look like the shaft can move in/out of the housing about 2.5".

Normal?

 

Question Was the truck on a lift?

 

Truck has not been on a lift and it has not been modified in any way.

 

No sorry was the pic taken while the truck was on a service rack.

 

Here is a picture of my driveshaft for a reference for you to look at. Your driveshaft appears to be moving alot more then mine. Hope this helps!

 

My driveshaft looks just like Champ's. Exactly like it. Nothing like Big Sarge's.

The driveshaft travels in and out of that primary transmission yoke relative to the amount of rear end sag caused by weight (trailer tongue weight). Before I installed air bags my rear end would sag 3-4 inches, then even more as I drive over bumps/dips in the road. This joint in the pic is where the suspension travel and geometry changes required for travel is necessary. (If I am wrong, please correct me).

Thing is, I have absolutely NO driveability issues. No vibration or strange feeling at any time at any speed. Now that I have airbags I assume that the range of motion for my driveshaft is going to be a little less.

Seems to be a normal condition in my opinion.

 

I haven't had a chance to pull my fifth wheel yet so I am wondering if the drive line shudder that was present in previous year models when heavily loaded has been corrected?

 

ruschejj, thanks for the info!

 

I pull a 14000# (loaded) fiver and have *accidentally* done as much as 85 mph, without noticing any driveline shudder. Maybe even faster than that... the truck has so much torque that I didn't notice the increase in speed until I looked down and saw the speedo. I let off the throttle and coasted to a more sane 70 mph . No shudder through any of that.

 

The shudder when loaded or towing isn't present at speed. It's noticed during acceleration from a stop or when climbing inclines. Look up "axle wrap" to read more about this.

 

The 6.4 I had would chatter a LOT biggziff. From a stop with a trailer, dash would shake as the transmission would put power to the ground, would go away once the initial energy required to get moving would ease off.

On my 6.7, nothing yet. Just smooth and even power unless I really go wide open, then there is a little more of a delay on the boost (very little). But never a shimmy of any kind. I only have 16K on mine so it's early yet. My '08 really started the shimmy later in its life, over 80K or so.

 

My '08 would shudder real bad when taking off from a red light with my Fiver in tow. I hope to find out Friday how the new truck does pulling the Fiver.

 

Is the truck of the OP a long LWB or SWB. I remember reading somewhere that a LWB will hop, so to speak, on the interstate because of the way some of the roads are laid out. Can't remember where I read that but it might be that.

 

Truck is a short base. Yesterday I got feedback. I insisted that a tech from my local ford dealer ride with me. I wanted to give the local guys a shot first. The truck hopped at 50mph. He said that is a characteristic of the truck and springs. He said he could road force check the tires but we both agreed that there was no vibration characteristic of a balancing issue. He then said there was probably nothing he could do. He told me I needed 200lbs in the bed. I told him that it already had 100 lbs in the underbed 5th wheel bracket and my 5th wheel hitch weights 198lbs when it is in the bed and I still get the hop. Both him and the service manager rolled their eyes and pointed to other Fords especially the F150's and said that I should see some of those trucks hop. At that point, I knew I was wasting my time with these folks. I said it was unbearable after a couple of miles at that speed. I thanked them for their time and left. I'm not accepting the fact that I can't cruise through town and not be "hopped" all over the place. I've noticed that hitting bumps and potholes will cause some bounce, but the hopping is incredible. I'm taking it to another shop later in the week if I can get up to Nashville soon.

 

My wife had a 1999 F250 on the F150 body style. It had a terrible vibration at 52 MPH. below or above that speed was smooth as glass. The dealer tried everything, balancing tires, changing tires and wheels, changing the drive shaft. Nothing worked to fix the vibration. The truck developed an oil leak at 29,000 miles and in the process of fixing that, they changed the torque converter. The vibration was gone after that. The vibration felt like the truck was trying to hop at 52 MPH. Something else you can maybe get them to try.