I need advise, broke axle/ big headache

Back in Feb I broke the rear axle .on my 2014 , 5100E John Deere tractor. Some water got in the main housing ,we drained all the fluid replaced the axle and filled it with new hyd oil , it turned milky shortly thereafter, changed hyd oil and filter again same thing ,milky. The J.D. mechanic said keep changing the hyd oil and filter using the expensive J.D. oil until it stays clear. Another independent tractor/ heavy equiptment mechanic said drain it , fill it with diesel run it for about 5 minutes drain the diesel and replace the filter and hyd oil.He said I don't have to use the high price J.D. oil. Comments please

I need advise, broke axle/ big headache