As these are plain helical cut gears, not hypoid like a car differential, you aren't going to set the preload the same way. The process for that is different now anyways; while we used to have to calculate shim stacks and offset the pinion based on gear clearance and correct contact region, most manufacturers have moved to a much simpler single shim based on contact area between ring/pinion, then the actual bearing preload is handled with crush sleeves. It's been decades since I last rebuilt a Detroit Locker and had to calculate shim sets...
Anyhoo... you're working on a rovatti T-series, right? T-80 size or somesuch?
http://rovatti.ricambio.net/site/pagece5.wplus?ID_COUNT=ce_5_home&LN=2&CEPV=Rovatti001&CELN=2&MP1=CE_3062&NDS=CE_3062&PRC=|R|CE_3076|CE_2|CE_3058|CE_3062&PRF=4#CE_3062
I tried looking up the exploded view so I could see the preload mechanism; that will usually give you some indication of whether it is intended to have actual preload, or cold endplay. Unfortunately, all the pics are horrible resolution, and after looking at a dozen different ones, all I saw was models that use only ball bearings.
Thanks mnem for your insights.
Yes it is a T80 and the exploded view is shit and incomplete as it doesn't show the preload mechanism for the taper roller bearings on the pump (output) shaft. The input shaft are just plain old ball race bearings so add nutthing in terms of drag however the pump shaft bearings are an entirely different kettle of fish in order to withstand the lateral loads on the pumps shaft which are from 70 HP drive loading, pump impeller delivery reverse thrust....< those to some degree counteract one another* and 3200 rpm operation.
* yet the pump side Timken is larger so indicates it has significant stress on it.
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No way would I put this together without some preload and to liken it to a hub bearing would be a mistake due to the rpm it's running at and instead of grease it's lubricated with HD EP gear oil.
It's likely we can check preload again after some service with out dismantling the pump head as we can access a portion of the pump shaft to wrap a string around it and check preload with the scales method.
However I think there's merit in your suggestion of some torque setting to the preload grubscrew as it seems the most logical due to its accessibility once the whole pump is assembled and there's a tiny locking grubscrew to fix the preload screw once its set correctly. Thinking out loud.....that's the most likely resolution to this preload puzzle as it's something that's piss easy to adjust whenever your mood says it need be checked.
Off to have a read of that nice Timken pdf.
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