Friction Modifier: When is it really needed?
My dad has a rumble coming from the read end of his 2000 Ford Expedition Eddie Bauer w/ 5.4L, A4WD, and air leveling suspension.
The owners guide says this:
"Your vehicle’s rear axle is filled with a synthetic rear axle lubricant and is considered lubricated for life. These lubricants are not to be checked or changed unless a leak is suspected, service is required or the axle has been submerged in water. The axle lubricant should be changed any time the axle has been submerged in water. Add 118 ml (4 oz.) of Additive Friction Modifier C8AZ-19B546-A or equivalent meeting Ford specification EST-M2C118–A for complete refill of Traction-Lok axles."
Now, on Amsoil's site, it lists two type of rear diffs for that engine, one takes the modifier, the other doesn't. For the diff that doesn't take the modifier, obviously don't add any. For the one that takes the modifier, Amsoil doesn't say either way to add it...but that they make note of it seems to suggest it should be added. On the 75W-140 Severe Gear page, it does have this little blurb, "AMSOIL SEVERE GEAR® is compatible with most limited slip differentials. If limited slip differential chatter occurs, add AMSOIL Slip-Lock™ friction modifier additive." So that seems to suggest not adding it unless there's a problem.
Royal Purple and Redline say they don't need it.
Not sure about Mobil-1.
Really, I'd like to use either Specialty Forumlations (which I don't think is back in business yet), Redline, or Amsoil.
I know which viscosity I need, I know how much I need to order, what I don't know is just whether I need this FM...and that's k1lling me because I'm thinking the rumble he's getting is from the FM not having been added - or added in too small of an amount, or, maybe just degrading over time - so I want to make sure I get this FM thing straightend out before I change it.
Anyone have thoughts on this???
Chuck
My dad has a rumble coming from the read end of his 2000 Ford Expedition Eddie Bauer w/ 5.4L, A4WD, and air leveling suspension.
The owners guide says this:
"Your vehicle’s rear axle is filled with a synthetic rear axle lubricant and is considered lubricated for life. These lubricants are not to be checked or changed unless a leak is suspected, service is required or the axle has been submerged in water. The axle lubricant should be changed any time the axle has been submerged in water. Add 118 ml (4 oz.) of Additive Friction Modifier C8AZ-19B546-A or equivalent meeting Ford specification EST-M2C118–A for complete refill of Traction-Lok axles."
Now, on Amsoil's site, it lists two type of rear diffs for that engine, one takes the modifier, the other doesn't. For the diff that doesn't take the modifier, obviously don't add any. For the one that takes the modifier, Amsoil doesn't say either way to add it...but that they make note of it seems to suggest it should be added. On the 75W-140 Severe Gear page, it does have this little blurb, "AMSOIL SEVERE GEAR® is compatible with most limited slip differentials. If limited slip differential chatter occurs, add AMSOIL Slip-Lock™ friction modifier additive." So that seems to suggest not adding it unless there's a problem.
Royal Purple and Redline say they don't need it.
Not sure about Mobil-1.
Really, I'd like to use either Specialty Forumlations (which I don't think is back in business yet), Redline, or Amsoil.
I know which viscosity I need, I know how much I need to order, what I don't know is just whether I need this FM...and that's k1lling me because I'm thinking the rumble he's getting is from the FM not having been added - or added in too small of an amount, or, maybe just degrading over time - so I want to make sure I get this FM thing straightend out before I change it.
Anyone have thoughts on this???
Chuck