I would have to say its a clutch issue, but if your concerned its the trans you can drop the oil pan with the engine still in the frame and inspect the trans with out having to remove the engine and split the cases.

 

Hi, thanks for the info! Is it also possible to change parts in the trans by just taking the oil pan off? I believe my 4th gear is worn down and needs replacing, and would also replace other stuff if needed. Thanks again!

 

If the gear needs to be replaced you have to remove the engine and split the cases. Only the shift drum and shift forks can be serviced without pulling it.