2011 Kubota 2320HST. I was clearing sloped driveway using both rear blade and FEL, in 4WD. While pulling uphill on icy slope wheels started spinning and I stomped on differential lever a few times - not realizing that is not the proper procedure! Later I discovered that the rear wheels were sometimes not pulling at all and sometimes intermittently. I have just purchased a repair manual online. I'm hoping it's just the external linkage but from what I gather on forums, etc. probably not. Will have a better idea once I remove panels, etc. Advice on determining issue? How to check CV shafts?