Rear Diff Fluid????

[jlrapp8]

ok. so i have a 2002 mountaineer 4.0L AWD with limited slip. i changed the rear diff fluid a while back and did mobil 1 75/140 full syntheic with friction additive. so i was at my local repair shop today with a different car and i was talking to them about my mountaineer. and the guys told me there i SHOULDNT of used the full syntheic in it. they say to just use regular stuff with the friction modifier. they are a honest repair shop i have been to going to for YEARS. and i know they wouldnt stear me in the wrong direction. i even talked to a really good rear end shop in my area and thats all they do is rear ends and they said the same thing. they said the full syntheic causes the bearings to go out quicker. just wanted to get other peoples input on this. cuz i have seen alot on here about only using the full synthic. THANKS

 

[2003vstrom]

if I remeber right the the owners manual calls for full syn. oil, I replaced my limited slip plates with carbon fiber ones and used valvoline syn power 75-90 and friction modifier and its been fine for the last 4 months

 

[jrford]

supposedly from the factory the rear is a full syn, and a 'lifetime' fill because of it. . .

But have you check on the schedule for a Dino? Years ago it was 12-24k between changes. . . yes if you did 12k changes with Dino it should last a long time. But at 75k miles i don't think it would hold up.

Also shops that use a lot of diff oil, the Dino is cheaper (its only my guess that they would use the cheaper one). . .look at it this way you rebuild 300 rear diffs a year, would you buy 600 qts at $5 or do you think you could get away with 600 at $18 a quart?

Another shop told me use 75-140w full syn front and rears. . . .maybe because no changes it? They also said some shops use the 80-90w in front only because its cheaper. .



Last change/fill on F/R i used 80-90w fronts, and 75-140w rears (open diffs so no modifier).

any information pls post it, i'm curious too. . .

 

[XCAMP]

+1 - You should use full synthetic, and add the friction modifier, according to the manual.

 

[jasongt06]

Sorry to tell you but they are full of it.

ok. so i have a 2002 mountaineer 4.0L AWD with limited slip. i changed the rear diff fluid a while back and did mobil 1 75/140 full syntheic with friction additive. so i was at my local repair shop today with a different car and i was talking to them about my mountaineer. and the guys told me there i SHOULDNT of used the full syntheic in it. they say to just use regular stuff with the friction modifier. they are a honest repair shop i have been to going to for YEARS. and i know they wouldnt stear me in the wrong direction. i even talked to a really good rear end shop in my area and thats all they do is rear ends and they said the same thing. they said the full syntheic causes the bearings to go out quicker. just wanted to get other peoples input on this. cuz i have seen alot on here about only using the full synthic. THANKS