Have Ford 9" with traction lock. Was told by a pretty reputable source that I should run 2 quarts Torco Gear Oil, and 1 qt Ford Motorsport Friction Modifier (no substitutes). Ford parts counter says their 4.5 oz bottle of regular Motorcraft Friction Modifier is the same stuff and a lot cheaper. They say 4.5 oz is all I need. Sure don't want to risk tearing up the rear end.
Originally posted by KULTULZ:
<strong>MOTORCRAFT Additive Friction Modifier XL-3 4FL. OZ. is all you need. Much cheaper (and same as) FMS.</strong><hr></blockquote>
Same reputable source (very well known rear end company) that gave the initial recommendation about FMS friction modifier says that I should never use synthetic gear lube because it will absolutely work it's way past the seals. What's your experience.
I get regular fliers from Randy's ring&pinion at the shop and the flier I received yesterday addressed the synthetic oil question. He strongly reccomends it, especially during break in, and he rccomends a break in period for new gears. He said that you should drive about 15-20 miles and stop for about 20 minutes for cool down, and strongly urges an oil change at 500 miles. I've never had break-in problems, but was interested in the synthetic issue. Synthetic isn't usually reccomended during break-in because it is too slick to allow parts to "wear" in, I've only encountered leakage problems in high mileage applications where seal are getting questionable.
Guys - I'm just about to add 75W90 Synthetic oil to my 9" posi rear end. Am I about to make a big $$$$ mistake??? I'm getting conflicting opinions on synthetic v. regular fluid. And what's the deal with the friction modifier??? I've never heard of that. Do I need it if I run synthetic.
Do not listen to the eggheads that tell you not to run synthetic in the rear axle. I use Royal Purple Max Gear 75/90w which has the limited slip additive already in it. No problems what so ever.
Guys - I'm just about to add 75W90 Synthetic oil to my 9" posi rear end. Am I about to make a big $$$$ mistake??? I'm getting conflicting opinions on synthetic v. regular fluid. And what's the deal with the friction modifier??? I've never heard of that. Do I need it if I run synthetic.
I use regular rearend lube in my 9"..real oil has been around a long time and I know it will work..
Friction Monifier is a additive used with trac-loc and posi's to keep the clutchs from chattering...
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