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    Rear diff maintenance

    I am getting mixed information on this from a Ford Dealer and from a Mercury dealer. I have a 97 Grand Marquis. I just bought it and I was thinking about doing a rear diff service (drain and refill). The owner's manual says, to do it at 105,000 miles. The Ford dealer says it does not have synthetic fluid and should be done every 30,000 miles. The mercury dealer says it does have synthetic fluid and therefore should be done at 100,000 miles. The car only has 77,000 miles and it is not making any noise. At another point in the owner's manual it says, the rear diff should not serviced AT ALL as in NEVER unless it has been in water.

    Any ideas?
    1997 Mercury Grand Marquis (just purchased July 09), 1993 Cadillac Sedan DeVille, and 2001 Ford Expedition (wife's car).

    #2
    My Dad always says that for an open diff, leave it alone, unless there is a percieved problem. If its a trac-lok, change the fluid periodically, using the proper friction modifier.

    If it has 77K on it, and its a trak lok, change the fluid. If its open, I'd just leave it alone.

    I did my open diff at 120K. There was no reason to do it.
    **2012 Ford Mustang Boss 302: 5.0/ 6 spd/ 3.73s, 20K Cruiser
    **2006 MGM,"Ultimate": 4.6/ 2.73/ Dark Tint, Magnaflows, 19s, 115K Daily Driver
    **2012 Harley Davidson Wide Glide (FXDWG):103/ Cobra Speedsters/ Cosmetics, 9K Poseur HD Rider
    **1976 Ford F-150 4WD: 360, 4 spd, 3.50s, factory A/C, 4" lift, Bilsteins, US Indy Mags, 35s Truck Duties

    Comment


      #3
      do you have an open diff or limited slip?
      Originally posted by gadget73
      There is nothing more permanent than a temporary fix.
      91 Mercury CP, Lopo 302, AOD, 3.08LSD. 3g upgrade, Moog wagon coils up front, cc819s in the back. KYB GR-2 police shocks. Energy suspension control arm bushings. Smog deleted.
      93 F-150 XLT, 302, ZF 5-spd from 1-ton, 4wd.
      Daily--07 Civic Coupe. Bone stock with 25k miles
      Wife--14 Subaru Outback. 6-speed.
      95 Subaru Legacy Wagon--red--STOLEN 1/6/13

      Comment


        #4
        I'd change it. You're not going to hurt anything by putting fresh gear oil in there. I would probably go to a synthetic fluid though, just so you know what its got.
        86 Lincoln Town Car (Galactica).
        5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

        91 Lincoln Mark VII LSC grandpa spec white and cranberry

        1984 Lincoln Continental TurboDiesel - rolls coal

        Originally posted by phayzer5
        I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

        Comment


          #5
          A 97 should have the standard gear oil in it. It will not hurt it to change, so do it if you want to. I would agree with gadget73, go with synthetic oil.
          89 CV LX 225/60 x 16 tires, CC819 rear springs, Front & rear sway bar, trans & PS cooler from 90 cop car. KYB shocks, F-150 on rear. Dual Exhaust w/ H pipe. Dark brown door panels, carpet, steering wheel, trim parts from a 87 Mer GM. Power front buckets from 96 Jeep Cherokee. LED'S front & rear. 3G Alt from a 97 Taurus wagon 3.0. Electric fan. Rear axle from a 97 PI 3.27 with disk brakes. Headlight relays.

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