by MFaulks » Wed Jul 07, 2010 8:25 pm
The box is strong the weakness are well known (5th etc), and treated with due care won't give any problem at your power level. The critical aspect is the bearing setup, and the production build appears variable at best, and some of the gear casings were not align bored very well. With a good casing, and new bearings and correctly set clearance on the two rear bearings you will not have any issue. As I have mentioned on here before, if you look at how the 5th gear oil feed has been gun drilled, it will almost certainly be offset badly to one side and wandering all over the place down the drilling - just plain crud QA and machining care. Moral - find a good one, probably all that was done for the Esprit - component inspection and selection.
There are plenty of mud hoggers putting far greater loads through this box in off-road racing, and they don't change the bearing type. I thought this was an issue but after a lot of correspondence with the Aussie fanatics they demonstrated that the bearing in the 610 is actually more prone to failure than the GTA. They also us the UN5 and this has the same rear bearing as the later box. They have some tricks in setup and rebuild where they do modifications, and they also offer gear ratios of your own choice, but the simplest tip - don't use the box for heavy engine braking when racing.
