I have 2400 miles on new 2008 450. At highway speeds or better, I loose significant control when driving on grooved surface. This always happens when the grooves go with the road, such as tire ruts of any size, or cuts in asphalt from resurfacing. This truck feels like I am driving on ice. Ford had the truck for a week and said nothings wrong. I have the 19.5 Continential ribbed highway tires. The wife won't drive it, say's it is dangerous. Is anyone else having these problems?

Nonprocutter

 

I haven't but then most dually trucks you will drive will act that way. My GM C5500 does the exact same thing on washboard style roadways.

 

How hard are the shoulders on your front tires? If they are still sharp, it may improve as the shoulders wear a bit. I do assume that you are running radial tires ?? I can't imagine anything else this day and age except for strickly trail rigs.

Have you modified the suspension at all, IE installed a leveling kit and then actually used your truck as a truck, with a load in the rear and with rear end squatting down? These trucks are picky as to frame slope, as that has a drastic affect on Caster, which can directly affect not only the recovery from turns (the steering wheel returing to center) but also directional stability. There is a reason why the rear sits higher on a truck (except those such as class 7/8 trucks with adjustable air ride) and that reason is to keep the frame slope proper, IE you never want the frame to slope to the rear for best handling.

And I have to add that blown65stang brought up a good point, most dually light and medium duty trucks tend to drive this way as a function of how the front axle is set up. Basicly you have a triangle going on, with the outer duallies wider than the front, so when you get into grooves or such, the front and rear of the truck is trying to climb up and out of the grooves at different times. Modern class 7/8 trucks have a much wider front axle, width the same as, or very close to the rear axle so they will hold the road much better than the smaller trucks, at least in grooves.

Nature of the beast to a certain extent, and way back when I was married, in all of my 16-1/2 years of marital bliss, my ex would not drive any of our dually trucks/motorhomes either because she felt it was unsafe. So I feel your pain.....

David

 

One last thing, depending upon the tire tread pattern, you may have to go to a different "ribbed" tire on the steer axles. You may have to try several differnt brands and or tread patterns. I have had good luck with Michilins (sorry for the spelling)myself, although the price is a bit much. I find the Toyo tires tend to wander more. I have no experience with the Continetal brand, other than on motorcycles.

David

 

Just a little food for thought... the 450 is just a little bit different from other duallys in the sense that the front end is much wider than traditional ones. The front tires actually line up closely with the outside duals.

 

I have an 05 dually but i dont really notice any loss of control type situations going over rough surfaces. I am also running stock tires.

 

I've noticed similar issues with my 450 as well. It also appears to be unstable above 75 mph. If you let off of the gas at those speeds the rear end will fish tail back and forth as if it had a flat tire. On highways with less than ideal pavement, even speeds of 60 mph can be a bit unsettling.

 

Tornitron, if you're running 4.88's or whatever the other gear setup is (4.30?) at 75 MPH while the engine is roaring at probably around 2400 or 2500 RPM, the engine braking will slow that beast down which could cause the rear end to sway back and forth as you describe.

 

This I would find unusual. Makes me stop and think a bit. Even with a jake slowing rigs down, or dropping a gear or two, I have not experienced anything like this on dry pavement on any rig large or small that I have driven. Hmmmm

I have had many experiences of hard sprung trucks bouncing all over the road when unloaded, but I have only experienced that when the road surface is rough...

I have some questions, any suspension "upgrades", whats the loading of the truck, are there roll (sway) bars front and rear, or trailer towing when this happens?

David

 

The truck is completly stock with no load or trailer attached.

 

Very interesting Tornitron, wow this one has me really thinking / stumped. hmmmm I guess I am going to have to do some research in exactly how Ford sets up / builds the suspension on these 08 F450's in relation to the older F450's that we have at work.

 

It might be the tires, I'm pretty sure that they are G load rated. That's a stiff tire and the tread dosn't flex as much with the pavement. Also, which tires did you get from the factory? The off-road tires that ford has avaliable for the 450's are not reccommended for highway use.

 

I have the traction tires in the rear. I wonder if perhaps that could be it. I haven't found anything stated that they aren't recommended for highway use.

 

I was told by a friend that works as a mechanic at Ford that the traction tires they put on the rear are just hard on the highway and can cause irregular handling. A few people w/ 450's had come in a said they had vibrations in the back and a "loose" feeling on rought pavement, and they all had the traction tires. Ask around and see if anybody else is having a similar problem and what tires they're running in the rear. Can't be positive, just second hand info.

 

I have spoke with a few F-450 owners who are reporting this issue with both the standard and max traction tires. While it may not totally eliminate the problem, reducing the pressure of the rear tires to 70 psi when not hauling/towing has helped in making the truck more stable.

This issue has also occured when towing/hauling, and in most cases a reducing rear tire pressure to only what is needed for the load has helped out. For this you will need your loaded rear axle weight and a load/inflation table to determine the proper psi.