So, I have 1999 3.0L V6 Ranger 4x2 with 125,000 miles and an automatic transmission. Everything is stock. Ive read my maintenance book and it doesnt give me an exact viscosity gear oil to use. Any recommendations and what brand is decent? Is it true that when I can feel the oil with my finger on the fill hole that its full? Thanks

 

Check to see if your diff has a limited slip unit in it. After you figure that out fill it with 80-90 gear oil until it spills out of the fill plug. If you have a L/S then you have to buy friction modifier additive. The book says 5-5.3 pints.

 

Can I use a suction pump? Where can I get one?

 

It would be a lot easier if you just drop the cover. All you need to seal it with is RTV.

 

I would just take the diff cover off. Fairly easy, just a bunch of bolts. You can get a gasket for where ever you get the gear oil. If you do it like that, you can clean any solid crap out of it, and also inspect everything in there. If its never been done then personally I would do that.

 

When I changed my differential fluid i used Mobil 1 Synthetic Gear Lubricant LS 75W-90. Then used some RTV to seal it all up

 

yeh, if you use a suction pumb, harbor freight has them super cheap. I used one the other day from HF for my brake fluid. I will probably do my fluid in the front diff with one tomorrow morning.