how much gear oil and what weight in rearend

[cenok is family]

just like the title says. i think my rearend gasket is bad so i want to change it and the fluid. i want to use royal purple gear oil as well, but i don't know what weight. i see 75w90, 75w140 and 85w140. and i hear you don't need friction modifier with royal purple oil, is that right?

 

[bynummustang]

Just use extra virgin olive oil, works great and makes it smell better.

 

[iapexl8r]

synthetic will help your clutches wear out faster. Use 85/140 with the friction modifier (perferably the ford stuff) if you have a trac loc possi. chris

 

[cenok is family]

so do i just need one bottle of oil?

 

[795.0pacecar]

It holds about 2¼ quarts.

 

[bloopbloob]

i'm running 75W90 royal purple, needed 2 bottles. I didnt use any friction modifier, and have had no problems so far. Its only been in there a couple weeks though. royal purple synthetic has a type of modifier already in it i belive.

 

[Darkwriter77]

What makes you think synthetic will wear your clutches faster? If anything, it'll make things last LONGER. Only reason why they'd wear 'em out is if you don't add friction modifier, which you should add in your rear end with ANY gear lube (synthetic or non-synth).

FWIW, I've had good luck with Mobil 1 75w-140 in all of my Ford 8.8's. Lasts a long time without turning into black muck like regular gear oil.