I was roading my John Deere 8400 MFWD to bale hay and noticed a harmonic like growling above 20 mph. It didn't do it all the time...kind of come and go and didn't do it under about 20 mph. I could feel it vibrate on the side console too. I was thinking maybe in the final drive or ring & pinion but still don't know where it's coming from. I baled some hay then headed back home and drove a little slower and didn't hear/feel the noise. I changed out the hydraulic filter and dumped it in a bucket and there is a lot of small metalic parts in it. I talked to a service tech at JD and they said they had a similar case a month or so ago and it was a final drive that was bad and to drain the fluid, check the screen and jack up the rear end to see if there is any slack in the bearings. Any other ideas?
TIA