Give it a try, if it is quiet and performs OK, then use it, you won't be far from home if it fails.

I have noticed what seems like lots of backlash on a number of differentials when just turning the driveshaft, and they have worked fine, so perhaps this is not an accurate way of diagnosing excessive backlash?

By just grabbing the driveshaft you would also be taking up the slack in the spider gears, axle shafts in the side gears, and the axle shafts in the hubs, this may all add up to feel like a lot, and the pinion portion of it may be small and OK?

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-