Tallica4life81

I have a 2016 v6 and swapping my 3.15s for 3.73s. I have the gear and pinion, new torsen lok since I have the 3.15s stock one doesn't fit 3.73 I have the install hardware kit Ford racing baring and seal kit what oil or friction modifier do I buy? I see stuff online that states 79-14 years on the friction modifier. I'm confused

jwog666

75w140 with a tube of anybodies friction modifier no matter who make the modifier its formulated to the same specifications

PNYXPRESS

Who told you that you needed a new diff because the 3.15 one wouldn't fit the 3.73 gears?

jwog666

there are 2 different carriers for that differential, one works with 3.31, 3.55 & 3.73 , the other works with 3.15 gears. if you want to change ratio from 3.15 you have to also change the carrier.

Tallica4life81

Every website who sells the gears state not compatible with a 3.15 ratio differential - use differential M-4204-MT or M-4204-M.

Tallica4life81

I went with 75w 90 royal purple gear oil and Ford racing friction modifier. Royal purple website say to use the 75w90 on the Ford mustangs gt, v6, and eco

chipss36

I use the same in my built up 8.8 no issues, no whine.

Tallica4life81

Everything read where people didn't add the Ford racing modifier had grinding noise and those who did add it to the royal purple said they loved it and those who said they had a problem drained and refilled using the royal purple but added the friction modifier and all was better