B5000 grey market is more similar to later model B5100. Many of the front diff parts such as yokes,& drive shafts interchange between models, engines are the same bore and stroke.
We have a parts manual for B5000 refer to www dieseltraders.com.au
Cracked tyres are quite common, as rubber starts to perish over 15-20 years, especially when left out in the sun.The only known remedy is to replace the tyres. The rears should be
7-14 which you can usually obtain locally. The lugs will be smaller than the original rice tyre, but thats better for general use any way. The fronts are 4-10 from memory (size moulded in sidewall), which should also be available. It is important to maintain a tyre diameter(or rolling radius) to say within 5 % of the existing size, as differing sizes can throw the front/rear diff ratios out, and cause binding of the gearbox, . This can be tested by placing the tractor on a level concrete surface and push by hand in neutral. You will notice if gets really hard to push as the gear start to load up.If the front drive lever is the selected to 2wd mode, a noticable thump comes from the gearbox as the gear is unloaded.
Some of our customers have replaced the lug tyres with road tyres (on the rear) of a similar diameter car tyre. Take extra care with diameters if you do this.
On grass or offroad there is some slip between the ground and tyre so any difference in ratios is not so obvious.This is only of academic intrest on a 2wd tractor.
Only use the smallest lightest slasher(bush hog) on these as they are fairly lightly built. The input drive spline into the gearbox is only small and can strip with age.The PTO drive gear are small as can be expected on a 10 hp tractor. If the slasher hits something the gears can break . But treated with a bit of care, they are remarkably hard working and reliable.
We have cleared large overgrown fields with B5000's, firstly by hovering the slasher, then cutting what was left.
A front weight is essential as the front lifts up when anything heavy is lifted on the rear hydraulics.
Treat them as the next step up from a ride-on and you should get many years of good service from if.