My thought was if this was in mud, sand, or gravel the drivetrain might survive. I have known mud trucks to run different front/rear ratios and it is a non issue because they never see asphalt. If the truck broke maybe 4wd was being used in a high traction situatuon
I would guess the ratio between front and rear was not far apart if they were different and it rolled easily even off-road. Guessing there also was no locker or posi track on either axle so it was the very typical 2wd 4x4. So as long as one wheel on either axle could break traction no issue.
To your point if you run 4wd on dry pavement even with matching axle ratios. Hard turns can cause binding and then can cause damage if some of the wheels do not break traction. (The tires start to turn at different rpms in a turn, the more the front wheels are turned the greater the rpm difference gets.) Thus why many manufactures state only to use dedicated 4wd in wet/snowy/off-road conditions where the tires can skid/skip/hop in a sharp turn.
Those with a viscous coupler (Automatic or full time 4wd high) either engage during the times when the rpm between driveshafts differs within a range of rpms, or allows for them to slip. (Rotate at different rpms.) Or both. Thus still delivering enough torque that gives power to both axles, allows for rpm differential between axles, but does not allow enough torque/pressure to overcome and break the drivetrain. VW, Audi, GM, and others offer this in different variations.
Back in the 80’s I bought a old Bronco. The PO hacked it together and one hack was putting a replacement axle in the front. But the numnut did not put the same axle ratio in as the rear.(Did not mention that either.) So with the large off road tires it fought itself front and rear and locked up on pavement when you put it in 4wd. Never made it to the dirt till that was fixed, but I would not have off-road it that way as it was not intended to be.
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