Is RedLine 80-140 gear oil (synthetic) safe to use in the rear end of my 73 Mav? I have some and I need to add some lube to the rear end. Or do I need to purchase some other kind?
in my experience i have seen some gear failure from synthetic gear oil. usually it was fords synthetic gear oil. my theory is that the synthetic gear oils are more slippery and not as sticky as natural based gear oil. the rotating action going at the intersection of the ring and pinon gears is pushing the oil away from them. the gears depend on the oil sticking to them and being able to stick to the teeth as they travel all the way around their rotation till they mesh again. ive worked on what is called a top loader diff. these are used in the top fuel and top alcohol race cars. they have a lid on the top that can be left off while the oil is in and you can spin the pinion and see what happens. at just by hand speeds you can see the section of gears that mesh, so imagine what its like at operating speeds. i use schafers gear oil in the jobs i do. its really sticky. if you pinch some between two fingers and spread them, the oil will string out between them. this shows that its sticky oil. synthetics dont do this. lucas gear oils seem to be really good also. red line seems to coat everything really well but its not stringy. these are my observations and experience in diff lubrication and i hope it helps all who read it to make the best decision for their diff.
Bryant, thanks for a reasonable explanation for why my gear guy says to not use synthetics. I put a tru-trac in my truck and previously used Royal Purple, and he strongly recommended that I use non-synthetic from here on out. I did not get it, no explanation. But your description makes sense. He still says to use friction modifier along with the non-synthetic lube. Even when there is no clutch material in the rear. So I do...
Thanks guys. I picked up a quart of 80w90 just to be safe. I'll leave the 80-140 for my Harley Tranny.
scooper, the true trac has no need for the friction modifier. you are just wasting money on it. only clutch type lsd's need the friction modifier. stp is very sticky stuff. wolfheads, it takes 2 to 2.5 quarts of gear oil to fill a ford 8" diff. i use a straight 140 wt in most diff jobs. the thicker gear oil will give more protection. it will consume a little bit more power but give more protection. now with the light weight of a maverick the 80w90 should be just fine. i use 220w in off road race trucks and use 90w in 4x4 front ends.
The guy gave me a 3 year 25,000 mile warranty that will void if I don't follow his directions. Not that he could probably tell if I used modifier or not.
