Aluminum housing and bronze worm gears? Sounds pretty fragile!
Just get a proper torque multiplier. They're $1500 at the industrial store, or $15 new at the plumbing shop.
Used it with a Snap-On 4ft long torque wrench that went to 600lb-ft. 
That is an expensive setup!Are they a similar design (worm gear) or do they use planetary gears?
I think that the proper ones use planetary gears; a snapon or proto catalog could probably confirm that.
The plumbing shop versions have no moving parts at all, of course.

I always wondered how those torque multipliers worked?
