I have a 97F150 XLT with 58900 miles on it. On saturday I went over a speed bump and almost immediately after I heard what sounded like a bad u-joint thunk from the rear end. The next day I checked the u-joints and they were fine. I also check to see if the brakes may have come loose, not it either. But I found there was a lot of play in the rear axle shafts in/out. What is acceptable movement for these axles. I use the truck for towing my horse trailer and other things. I bought it with 48000 miles on it earlier this year. The truck came with the heavy duty towing package stock. when I bought it I did buy the extended service contract adn they want me to take it in tomorrow. I was wondering if anyone has ever had this problem, or if they'd heard of it before?
thanx

 

when you take it in ask them to pull the cover and check it out...least of all you'll end up with fresh fluid and modifier...but if you start hearing a whine on acceleration or start smelling rearend fluid at the rear wheels after a drive you'd better take in

 

the in and out thunk is normal, (alot) that is how it is designed,

 

barf,

The design of a semi floating axle allows a little play in the shafts. These units have a pin in the center of the differential that stops the axle shaft from moving inwards, and a C- clip (looks like the letter C) on the shaft in the differential that keeps it from sliding outward. There is usually about 1/8 inch of play in the shaft, but the clips and spider gears can wear. If you feel that there is an excessive amount of movement in the shafts, then bring it in to have it looked over. These C clips can fall out (extreme case) given enough play in the shaft, and then the whole shaft can slide out of the housing. Good luck!