MaddogBC
Kelowna BC
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Heading out on a 400 mile trip tomorrow and considering replacing the fluid in my rear Diff on a 1993 F250 with the 7.3l
I understand Synthetic Oil handles the heat better and will not break down as fast. Just got off the phone with the "sunday" Lordco guy and he tried to steer me away from 75/140 because of a higher detergent level.
The fluid is at least 3 years old and this is my first season towing heavy loads.
What would you recommend both for type of fluid and procedure to replace? Should I flush with cheap oil first? Thanks for your time
Rob
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BarneyS
S.E. Lower Michigan
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I think you will have better luck with this question in the Tech Issues forum. I will move it there.
Barney
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bill h
el segundo
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I would use a synthetic with the same viscosity the manufacturer recommends.
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smkettner
Southern California
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Mobil 1 75w140 is my recomendation. The autostore should sell a small hand pump to put on the oil bottle and fill the diff after you drain it. I would drain it by removing the rear cover. No reason to flush but you can use a rag to wipe out the small amount that will remain. Forget the detergent guy, he is all washed out.
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Dave H M
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Maddog,
Man you are messing with fire asking for advice instead of using the operators manual and get the spec from it. My 99 F250 called for synthetic and the best buy I got was Valvoline from NAPA. Also there was an addative for the limited slip.
I won't advise you on what to do but if the book is stil in the glove box, it will tell you what to use.
I don't know about the flush either. I had to take the rear cover off to change mine. All the old stuff ran out and I just wiped the bottom of the punkin out.
I would think the time to do it would be when not just getting ready to hit the road, but that is just ole reserved me.
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MaddogBC
Kelowna BC
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Went through the book cover to cover and it seems to skip the diff's
goes straight from engine to tranny to transfer case but no mention of rear end or differential. And yes I checked the index too!
My tranny guy talked me out of 75/140 so I used 75/90 penn synthetic @ 14 per L
Scraped off all the old silicone and installed a new gasket. Cleaned it all extremely well. Will find out tomorrow, but I'm satisfied. A little unsure how tight I should torque the cover back on, it was extremely tight. I filled it at 25 lbs per bolt and am leery about going tighter. Thanks for all the help.
Rob
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liborko
Surrey, B.C.
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Don't even think about anything else but SYNTHETIC. Ford factory fill is synthetic for the last several years. I use Mobil I synthetic 75W-90. Good for any axle.
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amxpress
Clayton, NC
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For future reference, it calls for 80W90 GL-5 gear oil.
If you have a Traction-Lok differential, you should add a 4 ounce bottle of Ford friction modifier, part number C8AZ-19B546A.
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82corvette
Southeast Nebraska
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Valvoline synthetic already has the additive for locking differential in it. I read the bottle after changing mine & adding the additive!
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Oldfordman
Marysville, WA
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liborko wrote:Don't even think about anything else but SYNTHETIC. Ford factory fill is synthetic for the last several years. I use Mobil I synthetic 75W-90. Good for any axle. Except those that DO require 75W-140.
The "Numbers" work the same for Gear Oils as for Motor Oils. The 75W is the same in 75W-90 and 75W-140. The difference is that the higher number indicates an oil that will provide better cushion for the gears at High Temperatures.
Gear Oils are not usually loaded with Detergent Additives because they aren't exposed to byproducts of combustion. Just lots of Extreme Pressure additives.
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