Nice project! That's good if the torque comes at higher revs, because it's the low end torque which kills these boxes/diffs.
And wrong kind of use, there have been blown diffs with stock engines when people try to do burnouts with underpowered engines and open diffs.. and in most cases parts have been very worn and with low oil levels. Like Foggy said, if you don't drive like an ape you should be fine.
Weakest link is the diff, small gears are prone to break in open diff with turboed 360s, but if there's not huge amounts of torque at low revs you should be fine. Also the joint between the torque tube and gearbox has been an issue sometimes with higher power setups, but apparently it can be reinforced too. But it's the open diff (small gears especially) which goes first if something breaks.
Box will handle the power, 300-series M45R/M47R box will handle the same as M46 box used in bigger turbo Volvos, only fifth gear is a bit weaker in M47 than the electric overdrive gear in M46.
In bigger turbo Volvos, torque numbers between 420 and 450 Nm have been considered to be the numbers when lifespan of the box is something between one acceleration and few weeks. So below +400Nm levels you are fine with the box.
And in lighter setup it's more easier for the box than it is in 240 or 740 Volvo.
Though Makkiver ran +400Nm +300hp from the crank in 360 for sometime before he upgraded to Getrag and BMW diff, and he didn't break anything. He had turboed 2.3l Volvo engine and power came at very high revs so that's one reason why he didn't break anything.
But 200lbs/ft (~278Nm) shouldn't be a problem if parts are in good condition.
Volvo R-Sport - Equipment for the car enthusiast.
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,what front suspension/steering arrangement will you be using?
