friction modifier LS 4:10 rear

[Byron Pletcher]

i will be replacing the fluid in my 03' trac with a 410 LS rear this weekend., i picked up my royal purple 75-140 and on the bottle it said "friction modifier added" i already bought the motorcraft bottle from ford..



i know i should not add my bottle ontop of the royal, although i dont want to void any warranty etc.. i would assume the royal purple additive would be as good as ford right?

 

[Johnny O]

I'd put it in without any addtional additive.

 

[Tom Schindler]

Does the RP say any Specs on the additive?



I used AMSOIL 75W140 gear oil in both our differentials. (Explorer and Trac) The bottle says that the modifier already added. I added it anyways. The rear end works flawlessly. Plenty of grip on both wheels and no chatter.





Tom

 

[Todd Z]

Honestly, Ford rears are touchy, Spend the extra $7.00 and get 1 bottle from Ford, To me it is not worth the chance...



I also have seen Ford rears act up with the "already added" fluid..



Todd Z

 

[Ron Tobias]

although i dont want to void any warranty

You may be already. Is RP "Gear Oil" API certified? Unless something changed recently, RP motor oil is, RP gear oil is not. Check your packaging & check their website. It must say API certified, not just a phrase that implies it's certified.

 

[EddieS'04]

When I changed the fluid on my '94 stang LS rear, I had to add the ford modifier. Even though the new stuff said modifier included, my LS clutches started chattering. The ford modifier stoped it.

 

[Byron Pletcher]

alright, i will check into it. I am not partial to RP i may just return it and run mobile1 w/ ford additive.

 

[Todd Z]

I am happy with the royal purple I used on my ST.....



I did my 03 with RP and my 04 with all Mobil 1... The RP was a little thinner so I see where the little extra friction reduction with the RP comes from..



Todd Z