Take the screen out of the bottom of the transmission. What color are the metal shavings? Brass? You're fixing to spend some money. Aluminum? You'll spend a little less money. No shavings? GO buy some lottery tickets-and a spin on filter and some super UDT2 to refill the system.
I already replaced the balancer , it might need more flux...... I have always only used super UDT 2 and Kubota filters. I am about 8 months late on changing the oil . I have noticed it seems better when it's not fully warmed up or when I am on fairly level ground.
As for more info, it's hard to describe , it is only on the right drive and it kinds shudders and make a noise almost like it's grinding gears , i know it's not but the best way to describe it....
i could pull the oil and screen this weekend and see what we have......
I had the same type of shuddering from my GR2100. The PTO clutch blew apart. I found a bunch of clutch fiber sludge in the screen. I replaced the clutch, changed the fluid and filters and was good for one mowing. Apparently there was additional damage inside--the axle seals are leaking. I bought the transmission rebuild kit and plan to tackle that this summer. While I am mechnaically inclined, this is not my area of expertise. Maybe @lugbolt will chime in further on what the problem is likely to be based on brass vs aluminum shavings in the screen.
GR2100 is not a ZD21, and a ZD21 is the subject of this post.
aluminum vs brass shavings. If it's just aluminum, the liklihood of a charge pump failure is high. When charge pump fails it fails to provide enough volume and pressure to the HST's, because of the design the RH side is affected first.
If any brass shavings, that means that the wear plate(s) in the HST(s) are worn, galled, trashed--it usually trashes the entire HST, and sometimes BOTH of them. If you see that, you're probably gonna have to replace at least the RH HST and hope that the LH one lasts a while. If (when?) the other side dies, it will then fill the entire system with junk just like the RH one did, and may take out the brand new RH one with it. Seen it a few times. Too many times to be frank.
While on the subject, the ZD21, and especially the ZD25 and ZD28 were known for this. The problem with them was multifaceted. They didn't hold enough oil. The oil cooler system wasn't efficient enough. The filtration system was inadequate. The charge pump was inadequate. The failures were "mostly" in the Southern half of the USA where the outside air temps get toasty. The service intervals were too liberal, in that the manals specified I think every 400 hours, when in all actuality it should have been about every 150-200 hours at the most. With that being said, if anyone still has one of these great dinosaurs, I highly suggest taking GOOD care of it, cut the service interval in half and use ONLY Super UDT2 with OEM filter, clean the screen every time you drain the oil. Those folks that maintained their stuff or paid the dealer to service them every year (residential use)--never had any issues out of them. Those that used junk filters and fluid, and thought it'd be ok to run a thousand hours on fluid/filters not so much.
Thanks for the info, I was going to change the oil and filters this weekend in fact I picked up the stuff at lunch. Then thought more about it and after reading what you posted it's going to be a waste of expensive oil and filter so I'm just going to load it up and take it to the dealer the first of the week.