Yanmar 32HP track hoe. need repair help

I have a little Yanmar Track hoe I bought for my grandson to play on. It had a #3 rod kicked out the side of the block. So I located a diesel 3 cyl used engine and installed it. little thing works great. And other than having to have seals replaced in a few cylinders, it works great. Well it developed a problem, the grease fitting that tightens the rubber track up on one side you can pump it tight with grease but as soon as you move the hoe it starts to loosen up right away. The actual name on it is Dong-Eun. It is a Japanese import, model number JAKO- 007 and is a 2002 model. I can not find any info on it on the net. I'm thinking a seal is blown. Any equipment mechanics on here that can explain to me how to replace this seal? Thanks in advance.

2B04386F-723E-4D8E-814D-F844990D53D9.jpeg

A0F9EE75-56B3-4DBD-BF36-AFE94585340A.jpeg