This works for me (note the spec correct 75w-85):
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https://www.summitracing.com/parts/red-50104?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-red-line-synthetic-oil&gclid=EAIaIQobChMIlsTYxqeV2wIVj8DACh0muguZEAQYAiABEgLQHPD_BwE
Mine takes a little over 3 also. I just did it 3 weeks ago so I remember for sure. No idea on the factory underfill, it likely doesn't have to be as high as you and I filled it but as long as I am not blowing gear oil out the breather or past the seals, I am good with it.So I just did my rear and it took 3.5 of those delvac quarts. Either I have an enlarged rear diff or those quarts are severely underfilled.
Also 2.5 qts came out only. Underfilled from the factory? I know its never been changed because the crush washers still had black factory paint on them
hows this stuff workin for you so far? Changes in mpg? sounds? noises?
Zoro, Amazon, summit. I posted the summit link a few days ago.
I’m sure it’ll do 100k with average use. I went 48k something on my TC, it was clean looking when I drained it. I didn’t do an UOA so no idea what kind of life was really left.
I saw the link and appreciate the follow up. Was more looking for local so I don't have to order it. If I have to order it, so be it, but going to try my local NAPA first.
I'm comparing Redline 75w-85 to Royal Purple 75w-90 I had in both diffs before. Marginally better MPG - yes. Sounds? I've no way to hear it under there. The whole drivetrain seem to run smother comparing to RP 75w-90.
Well after 3 days of running the delvac in the rear diff and ravenol 75w in the t case, I can say that the truck runs smooth. Again its most likely the fact the fluids havent ever been changed in the 1st 40k miles (I bought used 2 months ago) and the magnet in the rear diff drain plug was absolutely horrid when removed. Ill post back my mpg if its changed at all (getting 18 mpg mixed now).
Still have to do the front diff this weekend.
I have been using redline 75w85 for 10k miles now. It deffinentaly runs smooth, but i have noticed a slight whine in the front when in 4hi or 4 lo when in a slight turn. Only have 21k on the runner and havent used 4wd much more then driving in deep snow. My uncle swears by royal purple and says i should switch. If you research synthentic engine oil, red line doesnt have the best data numbers compared to ams oil, penzoil and royal purple. Mobil 1 is at the botten of this list with the worst results, but thats engine oil. So i have been debating if i should try royal purple max gear 75w90. I dont think redline is junk, i probably should check the front diff to see if it is alittle low. I know i didnt check it again after driving around a bit when i did the change, does anyone else hear a slight whine when in 4hi when in a slight turn under 10 mph?
I have been using redline 75w85 for 10k miles now. It deffinentaly runs smooth, but i have noticed a slight whine in the front when in 4hi or 4 lo when in a slight turn. Only have 21k on the runner and havent used 4wd much more then driving in deep snow. My uncle swears by royal purple and says i should switch. If you research synthentic engine oil, red line doesnt have the best data numbers compared to ams oil, penzoil and royal purple. Mobil 1 is at the botten of this list with the worst results, but thats engine oil. So i have been debating if i should try royal purple max gear 75w90. I dont think redline is junk, i probably should check the front diff to see if it is alittle low. I know i didnt check it again after driving around a bit when i did the change, does anyone else hear a slight whine when in 4hi when in a slight turn under 10 mph?

I have been using redline 75w85 for 10k miles now. It deffinentaly runs smooth, but i have noticed a slight whine in the front when in 4hi or 4 lo when in a slight turn. Only have 21k on the runner and havent used 4wd much more then driving in deep snow. My uncle swears by royal purple and says i should switch. If you research synthentic engine oil, red line doesnt have the best data numbers compared to ams oil, penzoil and royal purple. Mobil 1 is at the botten of this list with the worst results, but thats engine oil. So i have been debating if i should try royal purple max gear 75w90. I dont think redline is junk, i probably should check the front diff to see if it is alittle low. I know i didnt check it again after driving around a bit when i did the change, does anyone else hear a slight whine when in 4hi when in a slight turn under 10 mph?
I am also using ravenol 75w in the t case, runs smoother then 75w90. Im running redline 75w85 in the front and rear diffs and get 18-18.5mpg city. Some guys have said they had a slight mpg loss with 75w90 in diffs but its really a small margin of difference in thickness.
This is the first i'm hearing Mobil 1 has ever been rated as a bad oil. Everything I've ever seen has put Mobil 1 up there with the best oils on the market.
Mobil 1 is at the botten of this list with the worst results, but thats engine oil.