Rear differential fluid looks like mud

The fluid in the rear end looks like mud. I’m thinking the vent tube is clogged. I’ve changed the fluid three times now and it still looks about the same each time I change it. Grey soup. I’m riding dry trails but I don’t know what the history was prior to me buying it just over a week ago.

What do you use to clean it out? I’ve heard riding a few miles with diesel fuel will clean it but maybe there is a better approach.

’95 Fourtrax 300FW

Rear differential fluid looks like mud

The fluid in the rear end looks like mud. I’m thinking the vent tube is clogged. I’ve changed the fluid three times now and it still looks about the same each time I change it. Grey soup. I’m riding dry trails but I don’t know what the history was prior to me buying it just over a week ago.

What do you use to clean it out? I’ve heard riding a few miles with diesel fuel will clean it but maybe there is a better approach.

’95 Fourtrax 300FW