strange bouncing @ 50mph

My truck has started behaving oddly. At 50mph, not 49 and not 51, it will start to kinda buck and bounce a little. Like driving over a washboard or something. Drop a mile an hour, smooth ride, speed up, smooth ride. It seems to get progressively worse the longer i hold it. It's a bit more severe than annoying as 50 is about what I cruise at alot.

What could it be? Not RPM related as it doesn't do it in other gears held at the same rpm. seems harmonic in nature due to the exact speed and the fact it will get worse if you dont speed up or slow down.

i have some fabtech trac bars in the garage, haven't had the chance to put them on yet but I doubt that will do anything for it.

thanks for any things to check!

sounds like you might have thrown a wieght off your wheel. i lost a weight pulling once and on the way home i was real rough about 60 mph....but over that speed or under it the truck was smooth

that's entirely possible, i've been "playing" alot lately. didn't think about that. I'm about due for a balance and rotate anyway and the weights are the stick on type on the backside of the rim.

This is the famous 45mph bounce. Most of these trucks have it. Add weight to the rear is what Ford told me to do.

That is a tire vibration. I would get them balanced before cause any unusual tire wear. Probably rotate them as well.

how about a seperateed belt in the tire

Mooring Product said:

This is the famous 45mph bounce. Most of these trucks have it. Add weight to the rear is what Ford told me to do.

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They all have that bounce. . .mine does it but not with a load.

I'm sure his speed o is off because of the larger tires. I would bet anything that this is what it is.

Try putting a load in the truck and see if it helps before you spend money on balancing your tires.

I have the bounce at 45-48 mph

Mooring Product said:

I'm sure his speed o is off because of the larger tires. I would bet anything that this is what it is.

Try putting a load in the truck and see if it helps before you spend money on balancing your tires.

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I don't normally carry a load and it just started not too long ago. My speedo is off by exactly 25% so the speedo actually says 40mph but I know I'm doing 50.

I've got some H1 wheels/tires I can throw in the back to see if that tames it. they weigh a ton. Either way I'll take it in for rotate and balance, im due.

Thanks all!