Curious what gear oil to run in my fresh 8 3/4/richmond rear end. Was using Valvoline 75-90 syn but was wondering if there`s a better choice..........thankxxx

I use 80-90 cheep stuff.

Did you change ratio?

I use Amsoil 75-90 when it's up to me. Have always had good results.

I use 80-90 non syn in my 8 3/4.. maybe you
should stick with what has worked since everyone
says that you should have blown it up

New 4.10`s and ya you may be right Mike, the Valvoline has been good 2 me...........

75/140 syn Valvoline has shown pretty significant temperature drops over 80/90 weight and its all I use, but, I wonder if heavier might be better in your case to maybe reduce shock loads? Is that even possible?

Ran the 75-90 syn Valvoline for 10+ years and the gears are fine and figured the thicker would rob et..........

i really dont think that it matters, i dont like synthetic though, it seems to leak too easily and is just too expensive. i just run cheap store brand stuff and have never had any problems.

Ever chassis dyno or do back to backs at the track to see what if any power/et is in syn oils including engine oils? I figured/hoped the syn Valvoline had maybe assisted in my junk living for 12 years street/strip w/a spool but who really knows............

I would recommend 2 cups of Henry's Roofing mastic. One cup of cheap cooking oil. And a half a cup sawdust. Kind of old school thinking but bulletproof

Naw, already tried that stuff and it didn`t work too well for me............

My 2004 Dodge Ram called for changing the rear gear oil at 20k miles. I drained it and it looked clear as new so I put it into my Satellites' 8 3/4" rear. It replaced cheap dino lube I put in there after I set it up. Figured it was better than the autozone crap I broke the rear gears in on.I'm bettin the synthetyic Chrysler factory lube with 20K miles is beter than the crap Autoaone sells.It is still in there after 6 summers and no problems so far.I think rear gear lube is so far advanced/engineered beyond what is required for survival that any choice is good enough.When did you last hear about a rear end failure due to lube deficiency?Buy the lightest syn. available and motor on .

Dom I've used Valvoline 80/90 as well the high dollar Richmond stuff. I have seen no difference. Next change going back to cheap stuff !

Guess I'm going to Ace hardware tomorrow..... can't argue, that dude is FAST!

Doc diff I think recommends 85w/140w conventional with the ford additive for sure grip. Not sure with a spool. I used Torco RGL 85w/140w in my street setup and like it a lot. I thought there were a few gear manufacturers that say conventional pulls the heat out of the ring and pinion better than the syn?

I use Lucas 80/90 heavy duty gear oil. When I had a 9" I used Redline synthetic.

Thankxxx guys, heading over to Pettis today so Jason and I can finish this thing up since he has a torque wrench that goes to 400ft lbs. and the pattern is giving me fits and I want to makes sure it`s right. I`ll grab some of the same Valvoline I`be been using and call it good.............Interesting about stating that dino oil transfers heat better than syn cos that goes against what syn motor oil does..........

Hey Dom,

I think that you're not loading up the gears enough to get a good pattern in the paint. But I have seen this before from guys doing this the first time. You're pattern is real close. Maybe not perfect, but close. Just like you told me about the air bleeds, that every .001" matters. It matters in your shim setup also. Maybe Jason has some thinner shims than what you have available. You are only off a small amount.

That`s why I`m heading over to his shop so that we can get it as perfect as possible then I`ll order axles tomorrow from Cass then off to the track............

Doc Diff/Cass will tell you to use 75/140.