chain goes ka-chunk!!
 

man, im having drivetrain issues as of late. running a 10 speed triple with 8 speed cluster and chain, seems great 90% of the time. every once in awhile in the middle ring, the chain seems like its sticking in the back, to the point of lurching forward. i thought maybe a freehub issue, but ive gone to town back pedaling and it seems fine. im running out ideas....also the chain and cassette are a bit old. casette more so then chain so perhaps those could stand to be changed. any ideas??

try putting some oil like trifol into the freehub . sound like the grease in it is getting hard .

interesting, the guy at the shop said something similar. so as grease get hard, does that make the pawls less able to engage? would that explain the slipping? i check out the chain for stretch and its fine, teeth on the cassette look good to. it totally did the lurch thing again so much so that it threw the chain off the middle ring while under load. its a fulcrum hub if this make any difference. im going to take it apart and inspect the grease situation.....thanks for the tip.....

I doubt it's freewheel related (though it could be). Freewheel problems usually cause chain spooling forward when coasting (jammed or sticky) or delayed engagement when starting to pedal after coasting (sticky pawls). Certainly flushing and relubing the freewheel mechanism can't hurt.

But I suspect you're looking at a chain problem. There might be a stiff link or two causing the chain to skip. Or possibly there's a worn chain or worn sprockets or both. That's most likely if it skips mostly under hard load vs. more randomly at any load.

I suggest you start by measuring your chain for stretch (lots of links and threads explaining this), and if you still have, measure the prior chain. Then keep track of when it skips because the details will provide critical clues. Does it skip on certain sprockets or chainrings, or randomly on any of them? Does it skip only under load? dors it skip only on large or only on smaller sprockets? Is there any kind of rhythm to the skipping, like once every pedal revolution, more often, or maybe only once every three revolutions?

took the freehub apart and it was pretty gunked up. fulcrum uses a 3 pawl system and two of them were lying flat and flush with the hub, caked in super thick sticky grease. i cleaned it up and put a much lighter coating of grease on there. the pawls seem to spring right back into place now. it must be a hub issue. two weeks ago, it was indeed causing the chain to drop when coasting so something was sticking for sure. we'll see if this does the trick. if not, im dropping this pair of wheels off a bridge and letting them sink to the bottom of the river. i have a back of set waiting to go just in case....