There is a difference is in the front axle frame. This frame bolts to the engine and front axle is supported by it.
L3560 is different than the
L4060. It appears to be thinner material, but does have additional bracing that the 4060 does not have. Front axle is the same in the 3560 vs 4060. Front axle assembly gets bigger in the
L4760. HST case, mid case and transmission case is the same for all grand L 60's. These tractors do not have a frame like what comes in a truck. Engine and driveline housings are the frame for the most part. The
L3560 is shorter than the others because the engine is shorter. Three cylinder vs four. Cab is the same for all of them.
My
L3560 came with the LA805 loader. Somebody incorrectly stated the
L3560 only comes with the small loader. Not true. You can option this on the Kubota page.
With R4 tires the
L3560 and
L4060 have the exact same front tire. The rear r4 tire is smaller on the
L3560. I have r4's and the rear end width measure right at 72" wide with the rim set at the wide position. Axle gear ratios are different between the two. Outer housing on the rear axle are also different to account for different gear spacing. Same axle shafts. I think the larger versions starting with the 4760 use different shafts with more wheel studs for beefier wheels.
You can look at the exploded diagrams on the Kubota web page to see the differences in these tractors. All parts are listed and can be compared.