usually when you turn your wheels it will make a popping sound over & over, if its really bad grab the suspected axle & try to move it if its bad the axle should have some play in it. hope this helps

 

There is a good 1/4" of movement When I move the spline up & down. Lots of play. It clunks when it moves. It doesn't rotate smoothly.

 

You shouldn't have any play or clunking sound & it should rotate smoothly so I'd say its bad but I'm not sure if its inboard (inside near differential) or outboard (outside near wheel) though you should be able to tell by the play or when you take the axle out.

 

The outboard one is the with movement. Do I need to replace the whole assembly? The manual says that the outboard CV joint cannot be disassembled.

 

manual says that. so does my honda dealer. but i went and bought a gorilla outer CV joint for both sides of my 450 when it broke and i can tell you they do come apart and you can replace the outer CV joint.
it was not easy to come apart but it did and the new outer CV joints fit perfect in the cup. The race or cage was much beefier on these new joints.

this link shows the part in question. i didn't have to break the cage as mine was already broken. the gorilla replacement slid into place over the snap ring and onto the shaft. Disassembling an outer CV joint the hard way on a 1986 TRX350 - Honda ATV Forum

 

Gorilla Duty Outer Rebuild Kits

this is what i bought. i run 12" wide outlaws on the front of my 450 and havent had a problem since i changed to these CV's
changed them about 6 years ago.

Mike

 

oops. sorry wrong link

here ya go

Gorilla Heavy Duty Front Outer Rebuild Kits for Honda

 

I wasn't sure if it separated or not but what ever is cheaper is what I would do I'm not sure if you want to beef up your axles or not but I've seen the whole axles both joints & snap ring for $108 for the '13 models on eBay I'm not sure if the axles are the same or not though