It's looking like the final drive assembly on one of the tracks is not pulling , forward OR reverse , has a rattle when you try and make it rotate , If anyone has any experience with replacing or rebuilding this drive it would be a big help thanks in advance ,
Drain the oil and see what is inside. If there are lots of sparkles, its removal and disassembly time. I've not had one of those apart but would assume it like the old Dash 6 line of excavators. The track motor would then be an integral part of the final.