right then here goes

ive fitted new chain (correct length) new cassette and new chainrings. all indexing works sound but under heavy load say a short sharp uphill the chain jumps like its trying to jump onto the next smaller cog down.

ive fiddled with the cable adjusters back and forth but it still happens. it rides fine everywhere else but slips under heavy load

no stiff links in chain either. cant find the problem any idea ?

ta

bent gear hanger?

mech hanger bent???

damn to fast for me

I concur

oh meant to say lol mech hanger fine and on tight and and btension screw seems set right

Although the indexing is works under no load, perhaps it isn't indexed centrally? (exaclty below each sprocket, rather than a little to one side of each sprocket?)
Try re-indexing it?

Have you checked the hanger alignment or does it just look ok?
what frame is it? poor cable outer set-up on a full sus bike could lead to problems under power.
cruddy cables.

8 speed chain on a 9 speed block is the only other thing i can think of in the drive train??

the frame may be twisted/bent

broken axle?

cassette lockring loose
bent link in chain
freehub wobbling

im gonna fiddle with the indexing some more problem i have is i cant make it do it on the stand ;-( so its hard to fix.

the cables are pretty new only a couple of months anyway but i may undo them and give a service

mech hanger just looks straight but may be out i guess i have a spare so can try that . its a turner five spot

problem is tho i didnt have the problem before i swapped the drivetrain so im thinking it may be the indexing

must try harder lol

cable housing too short under a linkage. When you compress the suspension, it pulls the gear cable?

shouldnt be anything other than the new stuff ive put on or the indexing as i adjusted them when i changed the stuff ? its an odd one its like a big quick crunch and then its normal again. a lad looked as i forced it to do it on a climb and i said it was as it crunched it was trying to move to the smaller cog

i thinking it must be the indexing somehow

double check for one link with a damaged sideplate

would jockey wheels have anything to do with it ? as everything else is new