all limited slip diffs need friction modifier for the clutches or it will chatter bad. the bottle is like 8 oz. i think it doesnt take up too much room in the diff so you will still get the 2.75 or 3.75 quarts of lube in depending on what diff you have.
if you have an open diff you dont need the modifier
Originally posted by TerryK67 Does anyone know if we need the modifier with amsoil rear -diff oil??
My understanding is that Amsoil differential oil does not need the friction modifier. I added Amsoil 75w140 to my differential just recently and have not had any chattering. I have driven over 500 miles with the new Amsoil diffrential fluid so far.
The following is stated on the Amsoil web site"
"AMSOIL gear oils are formulated with friction modifiers for limited slip differential applications. There is no need to add limited slip or additional additives."
I changed mine out with Amsoil 75w140 about 6 months ago. Even though the bottle said the friction modifier was not required I added a bottle of it anyway. No problems so far.
Originally posted by TerryK67 Does anyone know if we need the modifier with amsoil rear -diff oil??
Hey Terry,
I think I just started to feel a little chatter when driving the truck around lately but I don't know for sure. We had snow here early this week and I don't know how much effect snow/ice/wet road conditions are having on my differential. I am waiting for better weather at this time.
Its not a bad chatter or anything. Its probably just the limited slip doing its job in these winter conditions. I hate the thought of adding friction modifier and losing the effectiveness of the limited slip. Im leaving it just like it is for now.
The chatter is happening on a regular basis now with good road conditions. I have some Amsoil friction modifier on the way. I plan on adding an ounce a week until the chatter goes away.
(but no more than 8 ounces I hope)
I changed my diff lube to Amsoil and the chatter started after a couple of days so I added a bottle of Amsoil friction modifier.
The chatter continued so I emailed Amsoil customer service and added another bottle of friction modifier. That still didn't cure the chatter completely.
Then I went to Ford and bought their synthetic lube and friction modifier and changed it again. That solved the chatter problem.
I have used the Amsoil diff lube without the friction modifier in 3 other ford trucks with the limited slip without any problems so I was surprised when this happened.
Originally posted by wiggles I changed my diff lube to Amsoil and the chatter started after a couple of days so I added a bottle of Amsoil friction modifier.
The chatter continued so I emailed Amsoil customer service and added another bottle of friction modifier. That still didn't cure the chatter completely.
Then I went to Ford and bought their synthetic lube and friction modifier and changed it again. That solved the chatter problem.
I have used the Amsoil diff lube without the friction modifier in 3 other ford trucks with the limited slip without any problems so I was surprised when this happened.
I am wondering if doing a flush before changing the fluid makes a difference. Mag-Hytec has installation instructions for LE fluid that recommends a flush before adding the new fluid. Maybe the Amsoil became the "Flushing Oil" before you changed to the Ford Synthetic and Friction modifier. Doing a flush might also reduce foaming when new fluid is added.
Well, I used two bottles of Amsoil friction modifier in my rear differential and it still chatters after 160 miles.
I added one more bottle so I have THREE bottles in my rear differential now. I will see if it still chatters tommorrow. I put a call into Amsoil for a tech to call me back.
If I can't get the chatter resolved then I guess I will try a different differential lube.
There is a TSB for the 9.75 rear ends in 99-00 F-150 that experence chatter. TSB#00-8-4 dated April 17,2000. It instructs you to replace the clutch pack with a new kit pn F75Z-4947-AA If you have a 99 or 2000 with the 9.75 (5.4) then have a look into this.
There is a TSB for the 9.75 rear ends in 99-00 F-150 that experence chatter. TSB#00-8-4 dated April 17,2000. It instructs you to replace the clutch pack with a new kit pn F75Z-4947-AA If you have a 99 or 2000 with the 9.75 (5.4) then have a look into this.
JMC
I have a 1999 4wd extended cab with the 9.75 (5.4) and 40,000 miles. The chatter did not occur until after I switched to Amsoil. Do you suppose it is just a coincidence?
Thanks for the TSB posting. I will try to find it. If you know of a free web site with these TSB's then please post the link here.
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Friction Modifier & Amsoil
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