I've since determined there is an electrc toggle switch, taking with a clutch, the tractor out of front wheel drive, just as there is on the 40 series, but the 40 series is power assist and front to rear tire ratio not nearly as criticle.. We're purchasing 2 articulating tractors in the 30,40,50 or 60 series and adding larger tires all the way around!
I kid you not, one tractor that we are considering purchasing to run a baler has over 14,000 lbs of
ballast in its 4 35.2/32" singles, almost the weight of the baler. Changing out the tires for the hay season is not an option, but a requirement.
Although in entirety the purchase of 8-10 tires, rims and possibly wheels (including that of the 40 or 50 series tractor) may seem expensive over the course of a few summers they will more than pay for themselves. If I knew the front to rear tire ratio, I might favor the purchase of the newer tractor, otherwise staying with the 40 series. We almost needn't the front wheel drive at all, except to carry rthe loader weight of a 2 ton 3 bale load placed on wagons. the tractor otherwise being used to cut hay.
Art