4310 JD tractor

New to forum but I bought a JD 4310 in 2002. Lately I've noticed when operating out of 4WD that in reverse particularly I hear a thunk as it were like a gear popping out though it does not pop out. It is however something you can feel but the tractor keeps moving. It is equipped with the ePowrReverser. It also has the electronic switch on the right side MFWD that lights when engaging 4WD if that means anything. Any idea as to what it is? I'm concerned that something is going to give way at some point and I'll be in a spot where I won't be able to move it. Thanks in advance.

Hi Befuddled2. Welcome to Net Tractor Talk.
I, for one, have never heard of that issue before, but I did want to welcome you to our forum. Hopefully another member will be able to shed some light on this issue soon.

Doc

Thanks for the response Doc. I've been feeling this for months now and can't figure out what it might be. I'm just afraid I'll be out doing something and it will go. If that is the case then I guess I'll know. Thanks again for the welcome.