Today I had a clunk sound happen when I shifted into reverse it only happened one time and the truck had been driven for a little bit about 5 to 6 miles shut it off went into the bank came out started it up put it in reverse and herd the clunk sound. What could it be?

 

was it parked on a hill or against the curb? Mine typically will clunk into gear with either one of these situations and the parking brake isn't engaged before you put in park and disengaged after it's in gear.

 

No it was a flat level parking lot and I didn't use the parking brake by mistake as I use it 99% of the time when I park it the !% of the time I don't use it is when I forget to set it every once and a while when I park it for a short time like I did at the bank yesterday.

 

Might be the Ujoint if it occurs over and over.