[Bayou Titan]

I use Mobil 1 75-90w. I have some difficulty refilling the rear differential because the spare tire is in the way. I bought a Flow Tool which is a clear plastic tool that screws onto the plastic Mobil bottle. You can twist it to turn the flow on and off and the flexible clear hose lets you see the fluid going in. This makes the process a lot easier. These are sold at almost every automotive parts retailer like Pep Boys, Auto Zone, etc. for just a few dollars. I think the pump thing you add onto the bottle would work well also.