should i use cruise control when descending?
When descending -- as in traveling down a grade? No reason not to use CC. The exception to this would be a steep grade, simple enough to tap the brake, the CC will turn off. Then if necessary, kick it out of overdrive until back on flat or relatively flat roadway. Then just 'resume' CC
As for the 'clunk' you might want to 1) check trans fluid 2) have a look at your U-Joints
What year was you F-150? Does it have a two piece drive shaft? My 2010 had the "clunk" from the day I purchased it new. Took two years for the factory to find the problem with a seal and special lubricant. Fixed at dealer expense and have not had a problem with the clunk since.
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