Changes make a noise (sounds like a hammer hitting) when engaging the d (drive) or or (rear) changes

First check your battery is fully charged. A starter motor takes a lot of voltage to spin an engine over. Usually around 9 volts on a 12 volt system. Do you get any other noises like clunks, 'machine gun' style clicking?
The sound your describing is possibly the starter motor spinning but not 'catching' the flywheel. You'll need to remove the starter motor for this to check why it's not engaging. It could be a worn starter motor or the drive teeth to turn the flywheel could be worn.
How old is the bike? Starter motors do wear out, especially if they are used regularly.

doesn't mean the transfer case isn't still trying too engage.even with the front drive shaft out.

you probably need new starter but if you can hit the starter with hammer or something it might start

seat now you talking here i answer questions about big yank tanks i do not know about very much but a nice decent car like a seat ? well its simple but it will cost ,firstly check the linkage ,all them plastic bits are a pain in more ways than one ,if they appear ok then you lower the gearbox down a bit by removing the end mounting and putting a jack under it then remove the metal cover on the end and the 5th gear is exposed then look to see whats wrong from this point ,could be the fork broke or a baulk ring and without a look i couldnt tell you

no it should not spin when is in 2wd thanks

when i hit a curb with my 97 cavileier and bent the center hub its made a noise something like the one you are describing i changed it to a new one and there was still a slight noise i took it back of and took a closer look and the new hub had a slight warp to it so i took it back got another one and no noise i think that your hub maybe faulty as well dont mark my words but it worked for me

yes i believe that you are right with the strut diagnose. i bet you hear a loud hammering noise also

My 1994 Vanden Plas makes the same noise. I know I need rear shocks. You do also!! Have the rear shocks replaced. Bilstein part number B46 1858 or Koni part  number 30 1377. Actually the Bilstein is the better shock and less expensive.

quick way to tell... next time it won't crank and just clicks... hit it gently with a hammer as you have someone attempt to start it... if all of a sudden it cranks.... it's the starter... replace it before it quites completely.

Robert

damage is possible if driveshaft does not have room for movement and slams in transmission. sounds like your pump is going bad