Don't forget the differential!

Yep, it was just like I thought. I don't think the RV has ever had a differential oil change. Sure, it's only got 70k miles, but it's been 34 years!!

I bought a Lube Locker Dana 60/70 differential gasket since I need to do a bunch of short oil change intervals (ie: 1,000 miles per fill) to clean it up. Differentials don't have filters like engines and transmissions, so clean oil is very important. It lubricates a LOT of bearings and gears. The gasket will pay for itself in RTV savings, since it uses none. It'll also make it super easy to change the oil next time, no scraping away used RTV.

I bought a Performance Tool W54150 pump at the local hardware store to make filling tidy. It's very slow going but it worked great. It fits most 1 quart and 1 gallon oil jugs, so it was a good purchase for future uses too.

I'm running $15/gal SuperTech 80w90 conventional since I don't want to waste money on expensive oil, just to run it for a few months and less than 2,000 miles.

So yeah, that's one of the first things you should do when you buy an old RV or other rear wheel drive vehicle, change the differential oil! Differentials are NOT cheap to have rebuilt, about $1,500! And finding a shop who will even do them can be hard to find unless you are in a fairly good sized city.

Freshly opened. yuck!!

The inside of the cover is nice and clean now!

 Refilling with fresh oil.

All done! (For this time)