shifting/ indexing gremlins in low range, gggrrrrrrrr

philcube

hi all,
i'll try to keep this as short as poss. while giving as much info as i can, so please bear with me-
i'm having trouble with shifting in my low gear range (biggest 3 cogs), i'm getting- no shift atall, or chain shifting 2 cogs with 1 click, long hesitant shifts, and loud rattling when pedalling. the shifting through the rest of the range is all good- quick, quiet and accurate.
the chain has no stiff links, and the mech/hanger are both straight, and the cable is not sticking in the outers.
my set up is- deore shadow m592 mech, hg50 cassette, kmc x9 chain, sl590 deore shifters. i have read an mbr mag article called 'sorting your rear mech' and followed it to the letter, still got the problems, this is what i did-
shifted to middle chainring at front/smallest cog on back,
undid the cable clamp bolt on mech, adjusted hi-limit screw
screwed barrel on shifter right in, then back off 2 turns, tighten clamp bolt on mech while pulling cable tight.
shifted up 1 click and fine tuned with barrel- all good so far,
shifted to largest cog and tried to adjust low limit screw, but the top pulley on the mech wont go all the way inline with the largest cog (about 2/3mm out) even with the screw fully 'undone'. as for the b limit screw, there's a 5/6 mm gap between the top jockey and largest cog, mbr says this is correct. im guessing the gremlins could be from the (slightly) out of line top jockey, but as i say- i cant get it 'dead on' no matter what i do with the low limit screw (it sits slightly towards the secoind cog by about 2/3 mm). any ideas wuold be welcome, thanks for your patience.

Koiler

is the mech aligned properly? if you wind the b screw all the way out, there should be no gap between the mech and the hanger. if there is, loosen the axle bolt, and with the b screw all the way out, rotate the mech so it sits flush up against the 'ridge' (where the b screw should touch the hanger) tighten it up, and index it again.

it could also be crud in the outers which may not be noticeable.

is the mech a new one? if you've fitted a shadow, where previously you had a normal profile mech, then you normally have to remove a small amount of cable from the final loop before it enters the mech. i had this problem and couldn't get it to index properly until i shortened the outer cable.

Koiler

also, thinking about it, are you SURE nothing is bent?

philcube

thanks koiler- i'll double/triple check that nothing's bent, sorry- should've mentioned the fact that everything came as stock on the bike (2010 rockhopper), nothing's been changed/upgraded and the bikes only done 70/80 miles tops.

philcube

thanx again koiler- i checked the mech for alignment like you said, seemed ok, but i thought i'd undo the bolt and re-tighten anyway. i then tried the indexing process again, and hey presto!!! gear shift heaven! low limit screw lined up perfectly, all gears working lovely

cooldad

Hallelluya It's a miracle