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First time AC HB212 owner - a few questions


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I recently picked up a new-to-me A-C HB212 as a winter project.

The BGB had too much play in it, so I removed, drained, and inspected it. The keyway on the drive gear is excessively worn. As far as I know the only option is to replace the gear, and the gears are eye-wateringly expensive. After I go through the considerable expense of solving this issue, is there anything I can do to minimize wear and tear of the BGB in day-to-day use? Seems like they're a common problem on these tractors, and I'd rather not have to replace that gear twice!

This tractor has a vickers hydrostatic rear end. According to the research I've done so far (please correct me if I'm wrong!), parts are unobtanium so it's in my best interests to keep this system functional and take as good care of it as possible. Does the vickers hydrostatic rear end have any known issues or shortcomings? Anything I should keep in mind or that I ought to do to prolong its life? Is it worthwhile trying to find a parts tractor with the gear-driven rear to have as a backup?





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The original A-C HB212, same as the Simplicity 3112, came with a small BGB with 3/4" shaft. The later models starting with the Simplicity 3300 series came with the big BGB with 7/8" shafts. The small bevel gears and cross shaft are NLA from Simplicity. You may be able to find NOS parts.

The HB212 also has the mule drive PTO like the 3300 series. If you plan on keeping the tractor, I suggest converting it to a big BGB with the 3300 cross shaft as big BGB parts are still available. You would also need the bigger drive shaft flange, P/N 2172264SM and bigger clutch pulley.

In regards to the Vickers hydro, They were known to leak at the pintle shaft and the fix is to have it line bored and bushed. I think you would be able to replace it with a Sundstrand. Hopefully others will provide comments.

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just finished rebuilding the gear box in my Allis-Chalmers 716-6,it was not really a fun job.The parts were pricey and the bearings were difficult to find and when I did find them they weren't terriblly cheap. But on the other hand this part is the "backbone" of the tractor,it holds the two halves of the tractor together and is what drives the PTO.


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Thank you for the informative reply - it's good to know there's a more robust version out there!

I measured the input / output shafts on the gearbox today and confirmed I've got the "small" BGB with the 3/4 inch diameter input shaft. I took it apart, and was very pleased to find the source of the play in the shaft was a shmushed woodruff key, and that the gear surfaces all looked decent! The keyway is still sharp and well defined.

I'm going to clean up and inspect the bearings, re-assemble it with a new key and hopefully all will be well!

Another question: How much axial play should there be in the cross shaft when it's properly put together?

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The play should be fairly minimal. Looking at the edge of the PTO pulley on the LH side of the box, I think it should only move maybe a 1/4" or so between the mesh of the gears, 

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