I changed the oil in my '07 F150's diffs. I put in Amsoil Severe Gear 75W140 in the rear as specified. As per Amsoil recommendations I omitted the additive, but my diff "vibrates" when accelerating from a stop. I have since added a bottle of Amsoil Slip-Lok, but the problem persists. It is much better, but still there. Should I add a second bottle?
Amsoil Severe Gear in F150
- Thread starter atc250r
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Did you do a bunch of figure 8s......?
http://www.amsoil.com/techservicesbulletin/Drivetrain/TSB%20DT-2003-08-01%20Slip%20Lock.pdf
I would add the amount Amsoil suggests. No more/no less.
If you have limited slip chatter, you won't feel it going straight, only in a turn and mostly in a turn when you apply power. You'll feel it a lot, for example, accelerating around a turn. If you are feeling it in normal, straightline acceleration, then it ISN'T a limited slip chatter but something else. If you are feeling it in turns, then it could be LS chatter. Once you add the Slip-Lok, you need to do the figure 8s mentioned above. The additive takes a while to get between the clutch plates and those figure 8s do that more rapidly than normal driving. Do them and if you still feel the problem (in turns), then add another ounce, and try again, but add no more than specified per the volume of oil
My Eaton Posi only makes noises while coasting/power-off around turns (in other words NO torque applied to the unit at all) when it needs more friction modifier, NOT during power application in, at the apex of, or coming out of turns. 
My toy truck with a rear end from a 78 Firechicken has a clutch type posi and it has only made noise one time.
I came down an exit ramp off the interstate after a blast and it felt like the rear end was going to come out with the clunkin and chunkin. It did it only as i slowed and most if i was slightly turning.
Put in the whale snot and it quit instantly.
Originally Posted By: dailydriver
My Eaton Posi only makes noises while coasting/power-off around turns (in other words NO torque applied to the unit at all) when it needs more friction modifier, NOT during power application in, at the apex of, or coming out of turns.
Up in the cold North I would have used a 75W90 in the rear unless you do extremely heavy towing daily.
Also, I have a 250r in my garage in a pile. Gonna put it back together some day.
Originally Posted By: Jim Allen
Originally Posted By: dailydriver
My Eaton Posi only makes noises while coasting/power-off around turns (in other words NO torque applied to the unit at all) when it needs more friction modifier, NOT during power application in, at the apex of, or coming out of turns.
Originally Posted By: Jim Allen
That is very strange. Have installed a few late model Posis but I didn't live with them day to day. I wonder if it has something to do with the carbon fiber clutches. That kind of makes them a "different animal" in some ways.
Could be anything.
A clutch type posi chatters or pops, sometimes very hard and very loud as the clutch suddenly releases the play in the axle splines and spider gears over and over instead of the plates sliding over each other.
It's not really possible to hear noise inside the differential, only vibration transmitted to the body or other parts. I.E. gear whine or snap, crakle and pops.
We were talking specifically about the way the carbon fiber clutch pack plates behave in the Eaton Posi, and the noises they will make (whether transferred to the axle housing, and then to the unibody through the pickup points or otherwise) when there is not enough FM additive present for them to break loose freely on sharp, coasting, turns.
Originally Posted By: oilboy123
Did you do a bunch of figure 8s......?
http://www.amsoil.com/techservicesbulletin/Drivetrain/TSB%20DT-2003-08-01%20Slip%20Lock.pdf
Did 4 figure 8's.
All the clutch style posi units are the same old thing. I have worked on lots of them. I doubt the lining on the metal clutch plates is carbon fiber, if there is even any lining at all. They are usually embossed steel. But it dosent really matter what it's made of. They all just wear down over time.
Originally Posted By: Jeff_in_VABch
All the clutch style posi units are the same old thing. I have worked on lots of them. I doubt the lining on the metal clutch plates is carbon fiber, if there is even any lining at all. They are usually embossed steel. But it dosent really matter what it's made of. They all just wear down over time.
YES, of course they will also wear down over time, but again, supposedly not as quickly as the all steel clutch plates would.Update! So this past week the limited slip "chatter" came back. I haven't been comfortable with the 9 ounces of SlipLok I had to add only 15 short months ago. So yesterday I drained out all that Amsoil 75W-140 and replaced with Syngard 75W-140.
http://www.crossoil.com/syngard_gear_oils.php
It says in big bold lettering right on the front of the bottles that it meets Ford specs for the trucks. I also bought Motorcraft additive, but so far the diff is quiet and doesn't appear to need any additive.
I have had very good results with Amsoil 75W-90 oils, but this 140 grade was nothing but a head ache for me. Not sure why it required 9 ounces of additive in the first place, let alone why the chatter came back after 1 year and only about 5000 miles of no-load driving.
I just hope no damage to my clutches/gears have occurred from this fiasco...
Originally Posted By: atc250r
Update! So this past week the limited slip "chatter" came back. I haven't been comfortable with the 9 ounces of SlipLok I had to add only 15 short months ago. So yesterday I drained out all that Amsoil 75W-140 and replaced with Syngard 75W-140.
http://www.crossoil.com/syngard_gear_oils.php
It says in big bold lettering right on the front of the bottles that it meets Ford specs for the trucks. I also bought Motorcraft additive, but so far the diff is quiet and doesn't appear to need any additive.
I have had very good results with Amsoil 75W-90 oils, but this 140 grade was nothing but a head ache for me. Not sure why it required 9 ounces of additive in the first place, let alone why the chatter came back after 1 year and only about 5000 miles of no-load driving.
I just hope no damage to my clutches/gears have occurred from this fiasco...
Thanks for the update. Getting ready to change rear diff fluid in my '08 F-150. It also is spec'ed for 75W-140.
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