Reply to "How to increase the power handling of a ZF? (850 newton/meters or 627 foot/pounds)"

I agree, David. FWIW, with a very high torque engine, it's well known that the aluminum ZF cases 'spread' under load, moving the ring and pinion apart a bit and unloading the differential side gears- which usually fail. Originally, the GT-40 ZFs had cast aluminum side covers, no crossbolts in the access cover and no bellhousing brace-bolts. Those parts and more were upgraded to steel or cast iron in an attempt to stiffen up the ZF cases for LeMans, at the strong suggestion of Ford engineering. Ford went with a Collotti transaxle for the 427 GT-40s and had even more trouble with that POS.

IMHO, if you're going to go pro racing, use a pro racing transmission and put up with the fitment adaptions, shifting ills etc. The unsynchronized Hewland DG 300 (& others) was a popular replacement back in the day for F-5000, Can-Am etc, and the boxes wore out very fast but worked. Hewland is still in business in England and a quick Google search shows a few Hewlands for sale at ZF prices. There's no synchronizers because the gears are wider- which makes them stronger but requires even more care in gear-speed-matching than with the ZF.