there were 4 different ratchets in the pedal box, white, red, yellow and black and because it's been such a long time since i stopped fiddling with sierra's i can't be sure what colour is the correct one for the clutch that you need to use
it all depends on which pressure plate and friction plate you use, i'd recommened the large turbo escos one but then you have to ensure you have the correct release bearing to go with it, some are plastic and some are metal
back to the box though
you need to break down all 3 boxes and use the rear casing and gear selector from the dohc, insert the diesasal countershaft and 5th output shaft into this and use the input shaft and front casing from the xr version with the v6 bellhousing pattern
this is also where things get confusing because you need to use the flywheel AND FLYWHEEL BOLTS from the manual engine (you may need to buy new bolts if you can get them and you have to put threadlock on them, the auto ones have smaller heads, 16mm i think as opposed to the 17mm ones for the manual box, but more importantly they are longer) but more importantly there are several different starter motors, some with 8 teeth and some with 9 and some with 2 bolts and some with 3
DO NOT USE the 2.0 dohc starter as they ONLY fit the dohc 4wd engine/gearbox/flywheel as the gear is offset but as they will only fit the dohc 4wd it may be worth keeping as you can recon them
once you have bolted everything back together you will be able to fit a 2wd mt75 gearbox to your 24V engine AND use the 0.75:1 5th gear to replace the standard 0.83:1 5th which should be good for around 30mph/1000 rpm which, when i did it, had my speedo going way off the clock with revs still left to go (before i blew it up
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i think i had 8 or 9 boxes in my time, one lasted a whole 23 miles before it went kaput so what i would advise is to make sure you are able to drop the lump and box in one go as it's much easier to remove it that way that fiddle about trying to put 15 foot worth of extension on to get some some of the bolts at the top