I think your logic is right on. The front drive train on these tractors (I have a L2500) is not super strong.
When I bought my tractor, the splines were stripped on the front driveshaft, because the tires were mis-matched front-to-rear. That shaft is only 15mm in diameter, and is the weak point, along with the front and rear shaft couplers.
You can look up tire circumferences on the web, but I have found that they are not always the same as the product (the tire). I bought new Galaxy Earth Pro 45s for the rear of my tractor, and the rolling circumference was a couple of inches LESS than the published circumference. If I remember right, the F-R gear ratio for my L2500 is 1.6336.
I recommend doing a "rolling circumference" check.
1. Look up the gear ratio, front vs rear. There might be a reference for that somewhere in the OTT archives.
2. Find a fairly level, fairly straight 'track', about 150 feet long. Preferably, 'loose' surface, like gravel or dirt. (so when in 4WD, the front tires can slip if they need to, and not skid).
3. Put a stake in the track, either against the back of the rear tire, or aligned with the rear axle centerline.
4. Mark the tread of both a rear wheel and a front wheel. I like to do this at the very top of the tires, so that the mark is visible from the driver's seat. Spray paint works great.
5. Put the tractor in low gear, 2WD.
6. Drive down your track until the rear wheel goes around exactly 10 times and then stop. [make tick marks with a pencil and paper, so you don't lose your count.]
7. As you're rolling down the track, ALSO count the front tire revolutions.
Obviously, the front tire will go around more times than the rear tire will. This is your tire ratio, front to rear. For example, if the front tire goes around 16 times for every 10 revolutions of the rear tire, the ratio is 1.6.
Measure the linear distance between the stake you placed, and where the rear tire ended up after 10 revolutions. Divide by 10, and this is your measured "rolling circumference" for the rear tire. A 100-foot tape measure and a helper come in handy for this step!
Now, back the tractor up to your starting point, and repeat steps 3-7 while in 4WD. In 4WD, on a loose track, the front tires will slip according to how much the tire ratio varies from the gear ratio.
Now calculate the tire ratio again. If your gear ratio exactly matches your tire ratio (unlikely), then the number of revolutions of the front tire for 10 revs of the rear tire will be the same. Your tire ratio is the same as the tractor's gear ratio. Ideally, you want the front tires to go around ~2% *more* revolutions in 4WD compared to 2WD. In other words, you want the fronts to 'lead' the rears in 4WD. This improves handling in 4WD, and is not enough to damage the front drive train. I would still avoid driving the tractor in 4WD on dry pavement, especially if you have a loader installed (more load on the front axle).
You can compare your RC results to circumference book values for new tires, but the ACTUAL RC can only be known when you do the test, after the new tires are installed.
I'll see if I can find that reference in the OT archives and post it again here, if somebody else doesn't beat me to it!
-Paul
PS, the front axle housing on my L2500 has "L2250" cast into the back side of it, in 1.5-inch tall letters.
