Super Tech 75W140

[deano]

My rear diff is due for fluid change. Tag on diff says 75W140 synthetic only. I cannot locate Mobil 1 in this weight anywhere

, but while in Walmart I spotted 75W140 full synthetic in Super Tech brand. Anybody recommend this stuff? I know little about gear oils, so any help would be appreciated. My rear end is 9.75 Ford with LS.
Thanks

 

[Whimsey]

You should be fine using it. But most likely you'll need to add the LS friction modifier sold by Ford dealers. Did you check out any "major" auto parts dealers? They usually carry Mobil 1 gear oils and other "known" brands. If you use Walmarts brand I would change it within 20-25,000 miles again. More frequently if you submerge your diff in water.

Whimsey

 

[deano]

Yeah, I have visited AutoZone, Advance, and O'Reilly's, they all seem to carry M1 75w90 but not 75w140. I did see some Valvoline 75w140, but didn't look at it close enough to see if it was syn. BTW, can you advise on how much friction modifier should go in when changing the rear end fluid? Is it measured "so many ounces" per quart of diff fluid? I'll do a search here since I'm sure it's been asked before. Thanks, Whimsey.

 

[Whimsey]

I believe Ford recommends 2 ounces of their friction modifier in the diff. But I think the container is 4 oz's. Ask the local Ford dealer what they do/recommend for LS rears in 9.75 diffs. If they don't say try 2 oz's first and do some figure 8's in a parking lot and then see how the LS reacts for a week or so. If you get "funny" noises then add the rest of the friction modifier.

Whimsey

 

[Boaz]

I have 3 quarts of Amsoil 75W-140 I bought for my Jeep Liberty. I am selling the Jeep and never got around to changing the diffs.

So if you want I can sell you the 3 quarts.

 

[montero91]

my '99 expedition manual calls for same 75w-140 and 4oz of modifier to the 8.8 and 9.75 inch rear axles. i used the walmart syn. but why wuold it need to be changed out sooner than the 60k or 48 mos. the manual calls for?