Thanks for all the great info. I have the grinding noise in 1997 250 Trail Boss 2wd and have tranny open. Replaced gears and dogs but shift fork discontinued. Ready to buy silent chain. Curious how the two largest different diameter drive gears work for fwd and reverse as they seem connected. Which gears does the silent chain go on? Any advice on assembly is appreciated.

Follow up. Put things back and saw how it works. Rev being gear to gear as noted in posts. Noted that silent chain middle teeth are slightly cocked in different direction. Is that normal?

 

Look at the sprocket teeth.Large tooth one for the chain,reverse is gear to gear with the other larger gear.

 

Thanks, just noticed the middle rows in the silent chain move freely from the outer rows. Going to get a new one as it likely stretched over 17 years. Thanks for your contributions to this forum.

 

So, haven't posted in awhile because I haven't had time to work on my project quad. I replaced the silencer chain and checked for any wear inside the transmission in the gears and dogs. Didn't see any messed up teeth and there was no loose medal shards. Put it all back together with new fluid and it still makes a grinding noise under a heavy load. Where should I go next?

 

If you've eliminated an outer sprocket or chain causing this,then possible you over looked an internal bearing that's worn. Some of the bearings in different model gear cases were Russian and Chinese mixture with Russian bearings being the worst to fail.I had to replace a few in some Trail Blazers that were junk.

 

What is the best way to tell if the bearings are bad? No obvious damage was visible. Should I just see if they spin well? I have replaced both outer sprockets and the outer chain in hopes to fix this problem. Thank you for your time.

 

Best way would have been to have inspected them closely when you had the gear case apart. Roll each bearing slowly,feeling for any roughness from the ***** or any noisy bearing,any discoloration from getting hot, feel how tight the inner bearing race was to the outer race of the bearing plus how tight the bearings were fitting in the cases.Before you tear back into the gear case I'd double check the clutches to see if the noise could be coming from there.Especially the rear clutch,ramp buttons and possibly the belt.