[CNHSS1]

to be fair, in terms of what power they will take, i dont think theres a great deal in it. Most seem to think they are made of cheese, but id disagree. Shaun ran 300+on a mk1 box which arent supposed to be very strong and yet the sxoc boys seem to lunch s13 and s14 boxes at less than 300-350 all day long.

the later the box, the better the bearings and oil manangement imho. the last s14 boxes have a sprung loaded baffle on the centre steel plate to stop the oil all ending up in the tailshaft area under herad acceleration and starving the bearings and gears of oil.
the earliest boxes (mk2 s12 and s13) have lots of large holes on the centre steel plate, and the later boxes have poregressively smaller or fewer holes until you get to the s14 boxes.

My breakages have been shifter related, the 5th/reverse selector fork is a cast ally item and wont take abuse! the other two selectors are huge chunky steel jobbies! since changing to a B&M shifter (genuine one) i havent even broken a selector. The B&M has its own detent springs in the shifter so stops the gearlever slopping all over the gate and putting side loads on the selector rods. Ive beefed up a spare selecore with JB weld to try and make it stroger but its in a box i havent fitted yet.

i clutch kick and give it the 'big 'un' on a launch in the hillclimbs and thats with 280hp, 10.5" wide slicks and a paddle clutch, so they arent as bad as soem make out.
I use cheap gearbox oil and replace it very regularly in an effort to help.
for lots of miles use ie road, ide use Redline Shockproof heavy duty oil as a great way of protecting the box further.