ilmor Posted May 28, 2015 Report Share Posted May 28, 2015 Sometime this summer I'll be installing a beautiful new diff cover and I'm wondering if you guys had any recommendations / suggestions for gear oil other that the Ford 75W-140 Synthetic and Friction Modifier. I see that both Redline and Royal Purple have products for this application. Link to comment Share on other sites More sharing options...
shel-b001 Posted May 28, 2015 Report Share Posted May 28, 2015 Sometime this summer I'll be installing a beautiful new diff cover and I'm wondering if you guys had any recommendations / suggestions for gear oil other that the Ford 75W-140 Synthetic and Friction Modifier. I see that both Redline and Royal Purple have products for this application. If were my choice it would be Royal Purple , have used it for several years. Link to comment Share on other sites More sharing options...
Larry T Posted May 28, 2015 Report Share Posted May 28, 2015 Mobil 1 https://mobiloil.com/en/gear-lubricants/mobil-1-synthetic-gear-lube-ls Link to comment Share on other sites More sharing options...
MyBlueHeaven Posted May 28, 2015 Report Share Posted May 28, 2015 I used Royal purple and the FR friction modifier when I did my gears and cover, no complaints, Will stay with them when I change out to 3.73's over the summer. Link to comment Share on other sites More sharing options...
Blown Away Posted May 28, 2015 Report Share Posted May 28, 2015 I am doing this tomorrow and using Royal Purple 75W-140. No need to add friction modifier as it already contains it. I've been told it is actually bad to add the modifier along with Royal Purple as it is too much modifier. Dan Link to comment Share on other sites More sharing options...
bmezz Posted May 29, 2015 Report Share Posted May 29, 2015 Bought my Ford racing 4:10 gears,Ford Racing Traction - LOK Limited Slip Differential w/ Carbon Discs and a new GT500KR Rear Differential cover had all installed on my SGT today.Used Royal Purple and Friction Modifier. I am impressed in the feel everyone who said I would love it....YOUR RIGHT!! Tomorrow I try it on the highway to see what the difference in the RPM is,will post when I check it. Also got the BAMA X4 Tuner with 3 tunes anxious to try them out. Link to comment Share on other sites More sharing options...
ilmor Posted May 29, 2015 Author Report Share Posted May 29, 2015 Looks like Royal Purple has the votes so far.... Link to comment Share on other sites More sharing options...
MyBlueHeaven Posted May 29, 2015 Report Share Posted May 29, 2015 I am doing this tomorrow and using Royal Purple 75W-140. No need to add friction modifier as it already contains it. I've been told it is actually bad to add the modifier along with Royal Purple as it is too much modifier. Dan Funny that you say the FM isn't needed with the RP gear oil, because all the kits you can get that come with Royal purple still come with the friction modifier. First time I've ever heard that. Looked at the RP website where they say the gear oil is formulated with a friction modifier additive, that no additional additives are necessary. I think if it was bad they wouldn't include it in the kits or would tell you not to use it. With the additive being directed to be used by ford I would not go by what RP says, like a lot of the posters on various forums have said, there is no way to determine how much FM is in the RP gear oil, so how do you know if it's enough? Just my .02 cents but I would rather be safe and use it, than not have enough and it cause issues. http://www.latemodelrestoration.com/item/LRS-4209FRB-K/Mustang-88-373-Ratio-Rear-End-Gear-Kit http://www.americanmuscle.com/373-gear-oil-kit-8609.html Link to comment Share on other sites More sharing options...
ilmor Posted May 29, 2015 Author Report Share Posted May 29, 2015 Actually if you dig around the RP website you will find that additional friction modifier is recommended if the rear "chatters". Link to comment Share on other sites More sharing options...
ledfoot73 Posted May 29, 2015 Report Share Posted May 29, 2015 Went with 4:10's around 2009. Used Royal Purple 75-140 but can't remember if I used the friction modifier or not. Link to comment Share on other sites More sharing options...
Blown Away Posted May 29, 2015 Report Share Posted May 29, 2015 Replaced the diff cover with the KR one today. Used Royal Purple 75W-140 and no modifier. As per Alex Mackenzie and another mechanic friend of mine, both say too much friction modifier is a bad thing. I trust both of them. Dan Link to comment Share on other sites More sharing options...
vapor08GT500 Posted May 30, 2015 Report Share Posted May 30, 2015 Yes, like Dan said, just out the RP in and be done. Great stuff, no issues even with road race cars... Alex Link to comment Share on other sites More sharing options...
bmezz Posted May 31, 2015 Report Share Posted May 31, 2015 Sorry,Guess I was off topic Link to comment Share on other sites More sharing options...
ilmor Posted June 1, 2015 Author Report Share Posted June 1, 2015 Anyone have any experience with a tuner? I bought an SCT X4 Power Flash Ford Programmer it does not load the tune, when I go to device info it says preloaded tuning disabled I assume that's why it doesn't load but I can't switch so it's on. When I go through the procedure it says it worked but does not start I return the stock tune and it starts. Link to comment Share on other sites More sharing options...
Robert OHara Posted June 1, 2015 Report Share Posted June 1, 2015 Just added RP after replacing these new Eaton diff & Moser axles Link to comment Share on other sites More sharing options...
Lucy Posted June 2, 2015 Report Share Posted June 2, 2015 Looks like Royal Purple has the votes so far.... Didn't know we were taking any vote, but I'll cast mine now. Motorcraft 75-140 with friction modifier = 1 vote. I believe in changing oils and fluids more frequently than most, but in the long run, this pays off for me in other ways. Surely, engine oil benefits from my habit ie. Clean is the best. Rear end lube is a bit different, it is less affected by contaminants. I'll take down the cover once a year to give things a look-see and replenish the gear lube at that time, unless a mod or repair has called for that within the past year. The recommended Motorcraft lube with the correct FM makes this a bit easier on decisions about when it's needed or not, and the cost of the lube is a tad easier on the pocketbook as well. I have yet to see any proof that the RP, Amsoil et al...products are any better, and it will be a while before I take Ford engineers on in any debate over it. Likewise with engine oils, brake and tranny fluid, the latter being more complicated than any of them thanks to a sealed tranny fluid system. Just my .02c, y'all be safe. Link to comment Share on other sites More sharing options...
Dig-It Posted June 2, 2015 Report Share Posted June 2, 2015 Another "vote" for Ford Motorcraft. It is cheaper and works just as well as any aftermarket stuff. I use it every season in my BOSS 302 track car. Link to comment Share on other sites More sharing options...
ilmor Posted June 2, 2015 Author Report Share Posted June 2, 2015 Good points on the OEM Ford gear oil. I'm visiting my dealer for the air bag replacement on the SGT next Monday so I'll check their prices out of curiosity. Link to comment Share on other sites More sharing options...
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