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    Driveshaft Critical Speeds?

    I'm looking for the critical speeds of both the stock steel and aluminum driveshafts.

    Absent of the actual RPM numbers, it would be interesting to know what differential ratios were coupled with what driveshafts. For example, I've got my differential out, ready to put in some 3.55's. What was the highest differential ratio that came with the steel driveshafts? Did 3.55's only come with aluminum driveshafts?

    I sometimes bury my speedo, and I don't want to run higher than the critical RPM of my stock steel driveshaft. So, I gotta know, mang!


    HO with Explorer Cam, Electric Fan, Cop Sway Bars, Dual exhaust with no mufflers, 15x7" American Racing; 215/70R15's front, 255/60R15's rear, 3.55's with Trak-Lok.

    #2
    My car should have had a 3.55 and had a steel shaft. I put 3.73's in it and ran it constantly up to 115. No issues...

    But I do think most towing package/HPP (K code) cars all had aluminum shafts...
    Builder/Owner of Badass Panther Wagons

    Busy maintaining a fleet of Fords

    Comment


      #3
      Originally posted by mrltd
      My car should have had a 3.55 and had a steel shaft. I put 3.73's in it and ran it constantly up to 115. No issues...

      But I do think most towing package/HPP (K code) cars all had aluminum shafts...
      Kool! So I don't have to worry about getting an aluminum driveshaft. I don't think I'll be pushing 115.

      So, do you suppose that the aluminum shaft is mostly for strength, as opposed to a critical speed concern?


      HO with Explorer Cam, Electric Fan, Cop Sway Bars, Dual exhaust with no mufflers, 15x7" American Racing; 215/70R15's front, 255/60R15's rear, 3.55's with Trak-Lok.

      Comment


        #4
        Probably both. It migh not be needed, but it's a lot quieter and a lot less vibration. I have had my old steel one over 140mph (with 3.73's) unloaded a bunch of times...
        Builder/Owner of Badass Panther Wagons

        Busy maintaining a fleet of Fords

        Comment


          #5
          There are 2 versions of the aluminum drive shafts. One interchanges directly with the steel shaft and is for economy. The other is for the PI and tow packages and is stronger and is not a direct swap. Front is ok but the rear has a bigger flange. Both ends have bigger u joints. There might be a swap joint for the rear allowing the use of the smaller flange.
          Scars are tatoos of the fearless

          Comment


            #6
            My tow package car has a 3.55 gear, and the heavy duty steel shaft with the larger pinion flange. The aluminum stuff is avaliable on a Vic but I don't think it exists for a TC.
            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


              #7
              http://www.wallaceracing.com/driveshaftspeed.htm
              http://secondhandracing.com/Home.aspx
              http://secondhandradio.com/

              R.I.P. Jason P Harrill 6-12-06

              http://www.grandmarq.net/vb/showthread.php?t=5634

              Comment


                #8
                Ive got the heavy duty aluminum shaft. Need a flange though.
                1989 Grand Marquis LS
                flat black, 650 double pumper, random cam, hei, stealth intake, Police front springs, Wagon rear, Police rear bar, wagon front ,exploder wheels, 205/60-15 fronts 275/60-15 rears, 1 5/8" headers, 2.5" offroad x pipe, Eclipse front bucket seats, Custom floor shifter, 4.10 gears, aluminum driveshaft and daily driven. 16.77@83mph

                Comment


                  #9
                  Originally posted by DuceAnAHalf
                  This link does not good unless someone knows the wall thickness of the driveshaft . . . ?


                  HO with Explorer Cam, Electric Fan, Cop Sway Bars, Dual exhaust with no mufflers, 15x7" American Racing; 215/70R15's front, 255/60R15's rear, 3.55's with Trak-Lok.

                  Comment


                    #10
                    Originally posted by 89GrandMarquis
                    This link does not good unless someone knows the wall thickness of the driveshaft . . . ?
                    id go with the default.
                    http://secondhandracing.com/Home.aspx
                    http://secondhandradio.com/

                    R.I.P. Jason P Harrill 6-12-06

                    http://www.grandmarq.net/vb/showthread.php?t=5634

                    Comment


                      #11
                      My '90 had a K-code and a steel shaft. I don't think I've ever come across an aluminum one in any of my cars. Even my P72 has a steel shaft.
                      Save a seal, club a liberal.

                      Comment


                        #12
                        Thanks guys.

                        I just wanted to know if I needed (or should) upgrade to an aluminum driveshaft since I was going from a 3.08 to a 3.55.

                        Based on your input, I see no reason to locate and buy an aluminum driveshaft.


                        HO with Explorer Cam, Electric Fan, Cop Sway Bars, Dual exhaust with no mufflers, 15x7" American Racing; 215/70R15's front, 255/60R15's rear, 3.55's with Trak-Lok.

                        Comment

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