2006 Ford F150 V8 Four Wheel Drive Automatic 90,000 miles
If your going about 40mph and set cruise or push on the gas a little and let off the rear end pops and kind of bounces, this is the only vehicle I have that has done this could be bad U-Joints or something else?
Make sure you haven't been driving in 4X4. On hard surfaces.(And Didn't know it)
I am guessing you do not know how to check your " U" joints.
If you have 2WD you have 2, 4WD you have 4
Get your rig level and chock the wheel(s). In front of and behind. No can rolley either way!
Put you rig in neutral. Vehicle OFF. Crawl under
1 " U" joint is near rearend on drive shaft other 1 is at transmission/ tranfer case on the drive shaft.
4x4 is reversed, but at the frontend driveshaft.
TO CHECK: Grab the driveshaft side of the joint with one hand, and the differential side of joint with your other hand.
With " Opposing Force" with you hands, See if there is ANY MOVEMENT between the 2 yokes and at the center " +". Also look for damage at the caps on the ends of " +" (4 caps)
If there is damage or movement, its time for new " U" Joints.
I am a CJ guy and do not know your rig, your front wheel drive may not be set up like a Jeep or older 4X4s.A manual would really assist you, for this and future problems. Maintenece and trouble shooting. Step by step repairs.
This may not be your fix----this is the 1st place to start