Help Request: B2410 Diff Lock Operation

[NoJacketRequired]

Folks - I'm very nearly ready to pull the trigger on the purchase of a B2410 hydrostatic drive tractor. This tractor has fairly high hours (2500) but appears to be well-maintained and is in much better condition than most I have seen with that many hours on them. I normally would not consider a machine of this age but this one is in above-average condition.

My question to this august body is about diff lock operation. I suspect there's something funny going on but am not sure. Without ever touching the diff lock pedal, in 2wd the machine turns tight circles easily. Engaging 4wd (which occurs without any drama), those same tight turns result in the rear wheel on the inside of the turn slipping the gravel, like the rear differential was not totally free. I only attempted this on gravel, only at fairly slow speed.

Other data points. Turf tires are stepped quite far out on the axles, I suspect to provide additional roll-over protection as the machine has mowed a lot of grass in its time. Brakes are locked together and are fully "up", ie not engaged. Diff lock pedal is fully "up" as well. No other different or incorrect behaviors were noted.

Am I being hyper-sensitive on rear wheel spin in a tight turn in 4wd? Is this more like normal operation, or does this seem truly abnormal and should be considered a "no buy" deal-killer?

Thanks for your helpful comments.

 

[rjcorazza]

I wouldn’t worry about it while in 4wd. Clearly the diff lock is disengaged if it turns fine tight in 2wd. Hazarding a guess, perhaps the fronts pulling to one side in a turn is causing your observation of the rears.
Assuming the diff lock activates and releases I’d call it good.
JMHO


Sent from my iPad using Tapatalk Pro

 

[100 td]

Think of an AWD SUV
In AWD, drive goes to all 4 wheels, but there is an open differential between each front wheel and each rear wheel and another in the center between front and rear axles. Due to differential action the wheels can rotate at different speeds.
When you select 4WD, you lock the center diff, meaning you lock the front driveshaft to the rear drive shaft. So when you drive the same number of revolutions of the front axle combination must equal the rear combination. (This is the same as a tractor when 4wd is selected)
Now when you turn, the travel distance of your front wheels(the arc that they travel upon) is different to the rear wheels, but they have the same driveshaft speed, the front wheels have to travel further than the rear, so the rear wheel slips. This is the same as any 4wd with a locked center diff, that's why they say do not engage 4wd on pavement as it will bind up the transmission and possibly break something "if it can't slip" due to good traction with the pavement.

 

[NoJacketRequired]

Hmmm... Excellent explanation - thank you! I suspect I haven't noticed this on my other tractors because their tires are set in pretty much as tight to the frame as is practical, whereas the B2410 has them spaced as far out as they will go. This would certainly exacerbate the condition, given the radii described by the front and rear wheels would differ by an even larger amount.

Thanks again for your very thoughtful and helpful replies!