Gear lube question

mhissticobra

Member
Feb 12, 2004
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I need to know what kind of gear lube to use on my 96 Cobra. The 4.10's are finally going in soon after sitting in my room for half a year (plans on supercharging is reason for 4.10 and not 4.30) I was told by Autozone that I need 80w-90 but I wanted to make sure with you guys. Also, how much will I need of lube and friction modifer? Will any friction modifier do or just ford motorsport kind?
 
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You should only need 2qts of rear differential fluid and a 4oz. bottle of friction modifier.

Be sure to change the differential fluid 1,000 miles after they've been in there to get out the metal shavings from the break in period. BTW, you might want to refill it with synthetic rear diff. fluid after you change the fluid.
 
What the hell!!! - Royal Purple does not make 80W-90 in quart containers, only 5 gallon and 55 gallon drum!! What weight are people using for their rears, should I buy Valvoline 80W-90 or something??
 
mhissticobra said:
What the hell!!! - Royal Purple does not make 80W-90 in quart containers, only 5 gallon and 55 gallon drum!! What weight are people using for their rears, should I buy Valvoline 80W-90 or something??
You can always use synthetic 75w-90 from any good company like Amsoil, Mobil 1, Redline, Lucas, etc.

Yeah, you can use the Valvoline 80w-90. Just don't forget the friction modifier.
 
I believe Ford recommend synthetic 75W140. That is what I put in my car about a week ago with the 4.10s. Be sure to get the friction modifier. Ford sells that for like $4 per 4oz bottle.

2 quarts - Gear oil +
4 ounces - Friction Modifier
___________________________________________
= Smile on your face when those gears are installed
 
codyGT said:
I have always thought of synthetics in a clutch/cone differentials as a no, no!

Yeah, when I installed my gears, they put standard 80W-90 gear oil in there and after 1000 miles I switched to 75W-90 Synthetic and gear whine increased significantly. I switched back to 80W-90 regular gear oil and the whine decreased somewhat but I'm worried I might have created a mesh problem in the new gears by using that synthetic 75W oil for a few thousand miles.
 
STL00GT said:
I believe Ford recommend synthetic 75W140. That is what I put in my car about a week ago with the 4.10s. Be sure to get the friction modifier. Ford sells that for like $4 per 4oz bottle.

2 quarts - Gear oil +
4 ounces - Friction Modifier
___________________________________________
= Smile on your face when those gears are installed

The tag on the differential says 75W140 only

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