A friend's '02 Ram 4x4 1500 won't go into park. Someone told him it is a tranny problem. True?

Check the shift linkage adjustment. Is this an all of a sudden thing or has he been having trouble with it and has he made any recent changes to the truck?

4wd?t case in neutral will cause this. Course you wouldn't have drive either.

Shift linkage seems like the logical diagnosis but apparently it has been coming on intermittently and I feel pretty certain my friend would know it if the linkage was a problem. But you know what, I did not ask him just assuming his logical progression but I think it is still a good question for him.

Ask him if its hard to pull the shift lever into drive, or put it back in park. If the shift cable is getting bad, usually park is the first thing it won't go in. When you put the shifter in park, the linkage has to push the cable through the housing all the way to the end. If the cable is binding just a bit, it won't push it far enough to lock the park pin. There is an adjustment on the shift lever end of the cable, but if the cable is going bad, that adjustment won't fix it for long. Gene

He unhooked the cable/linkage at the tranny and the lever arm will not go into the park position.

Rooster comb detent/detent ball.

the bar for the band came off, need to drop valve body, reinstall bar and adjust band.

Reverse c-clip broke into three pieces. One piece went into the pan, one piece stayed in place and one piece got lodged in the shifting mechanism preventing it from moving all the way into park. The clip breaking is not unusual but I guess the piece getting stuck in the shifter is freaky.