I have been through it and back with my f150 the past few days. I've got a 2009 5.4L XLT screw with 116k (bought it brand new in 2009). Last night my driveshaft fell out at the rear end. The u-joint was so mangled from the break and from dragging on the asphalt it was difficult to decipher how it actually broke. but then again my truck has 116k, mostly highway. I had factory 18s when it was new and I had aftermarket wheels 20x10 on 33x12.50 mud tires and all terrains from 23k to 110k and recently switched back to factory 20s with toyo open country mt 295/65r20(35.4"x11.8") so im sure the heavier wheels and tires added stress. I have a K&N cold air intake and a superchips flashpaq tuner with the recommend K&N program that I purchased from superchips. Does anyone think this idea is crazy or is anyone on board with me here: I think overtime the added power put more than normal amounts of stress on the drive shaft causing the assembly to fail. So now am i not only $700 in the hole for new struts, rear shocks, and spark plugs, but i also had to prepay for the $690 driveshaft assembly. already ordered the new assembly and of course because its a special order it won't be in until wednesday. So does anyone think this problem will occur again? (i doubt ill have this truck for another 115k)

 

You should buy an aftermarket greaseable driveshaft and it won't ever happen again.

They are usually a lot cheaper by about $350 than fords parts.

 

Typically U-joints don't fail/go-out/drop-the-driveshaft without SOME forwarning noise (usually LONG before the event).

Did you just fail to heed it?

As for the added stress ... (lift assumed) Would suspect pinion angle and mileage were the major contributors.
.

 

u-joints fail, like other said there are warning signs. first sign is vibration and or noise. if you got over 100k you were running on borrowed time. just replace with a spicer, not that expensive if you do it yourself. everything you mentioned was past due to replace.

 

I'm interested too, seen to many fellow jeepers with lifts and no slip yoke eliminators, over flex and pull the shaft out of the tranny..