Re: Whicj rear end fluid?
Keith - 75w140 will work if the manual requests it. Rear end problems aren't generally caused by using the wrong weight gear oil. I know in Dodge differentials, the small clips were prone to come off around 90-100K. It has more do with how hard you run the truck. If you drive mostly with no load, cargo, passengers or trailer, then you'll have no problems. Synthetic will help dissipate heat better and allows for extended drain intervals over petroleum based gear oil stocks. If you carry heavy loads or tow above 60mph I'd definitely use the 75W90. If you occasionally tow and carry heavy loads 75W140 is sufficient. I own two trailers and my Dodge pulls them every weekend and some evenings during the week (side jobs!). I haven't had any problems yet - knock on wood, but Amsoil HD 75W90 is all I use. My truck hardly ever exceeds 65mph even when I'm not towing.
'11 Ram Quad Cab 4x4 SXT 5.7L HEMI (stock); 48,500m
'06 Pontiac G6 GT 3.5L 220hp; 64,000m
'12 Chrysler 200 Limited 3.6L 283hp; 28,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!