i had that clicking sound once too but all it was was the stock dogbones sliding a bit because i was missing the rubber washers that goes in the cups well hope everyone figures out those problems and 46u my dogbone doesnt slip out anymore and i havent change over too my new cups yet my shocks i had installed were not on the end mount hole where they should have bin i had put it on the hole just before the end but since i installed them on the end mount no more problems slipping out
ORIGINAL: 46u
If I am not mistaken the RTR comes with the largest spur HPI makes 52 teeth. The thing I keep going back to is he says it makes a clicking sound! Check the clutch, pull the slipper all the way apart and check it out. Then if you do not find anything go to the differentials. When you did like I said hold 3 wheels and turn the 4th did you use a little pressure on the 4th wheel when it go to point the wheel felt like it would not turn any more. Being I do not have the truck in front of me I am still guessing the diffs as he said about the clicking noise but I could be wrong. If I had in front of me I could tell really quick.
Good Luck