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for track wich is better dog leg gearbox or us spec gearbox

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  • for track wich is better dog leg gearbox or us spec gearbox

    i have both gearbox i want to know wich is better and i have 3.25 diff

  • #2
    the dog leg close ratio
    Mark Williams
    Dallas, TX

    Nothing says "welcome to the neighborhood" like a search... oh wait... looks like they are all gone! :rastajake:

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    • #3
      The dogleg in my opinion. Close ratios, 2nd - 3rd straight up and down. Top end will suffer a bit as 5th is 1:1, you'll get more legs out of the US box with the 3.25 diff but you'll need more power to get her there on a track.

      my 2c

      Aaron

      "But most of all...
      ... I like the way you move......"

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      • #4
        I will be the contrarian, if you asking for a track car. 3-4-5 is tighter and more consistent on the US box. You lose a bit of gear multiplication with the overdrive top gear. Get a 4.45 and call it a day, unless of course, you want a Grp A box, which has a very nice gear spread.

        Mike

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        • #5
          Use the US box and sell me the dogleg

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          • #6
            Dogleg is better, IMO. 1st is useless in either gearbox. At least with the dogleg, that useless gear is out of the way, leaving 2nd, 3rd, 4th and 5th in the standard H pattern. There is no need for an overdrive gear on the track, IMO. With 245/40/17 R6s, we are limited to 139 mph with the 4.10 and a 7800 rpm limiter. That's pretty good, and we have only hit that speed at Roebling Road. When I ran my M3 (with US box) at the Glen, it was a 3rd and 4th gear only track. I'd just touch 7500 rpm in 4th before braking for the bus stop (with 235/40/17 RA1s).

            At LRP, it was much the same. 3rd and 4th gear only. 3rd for Big Bend and the Left Hander, 4th entering No Name and leaving it there until Big Bend again. Basically, the Dogleg box gives you 3 usable gears, instead of 2 in the US box. The gating on the Dogleg is much tighter than the US box, especially the gap between 3rd and 5th. You've got to be careful on the 4th to 5th upshift. It also helps to have a completely fresh gear shifter/links/bushings/etc as well as stiff engine/tranny mounts. Once you've got the Dogleg in there, you can tune top speed with diffs. Sometimes it is best to tune top speed for the end of the longest straight. Other times it is best to tune for optimum power band through various corners, and sacrifice some top speed. That is something you have do decide yourself.
            Christopher

            www.brmmotorsports.com

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            • #7
              I'll play Devil's advocate along with empty. I am actually trying to decide which route to go, dogleg with 4.10/3.73 or 4.45 diff with the US box.

              I have recently driven a friend's car with the dogleg box, and the gearing is excellent in second third and fourth for probably track and autocross...

              Most of the JP racers in this area use the dogleg box and a 4.10 for shorter tracks in the South (Eagles Canyon, Motorsport Ranch, Hallett, Barber) which are mostly third and fourth gear and a 3.73 for Texas World Speedway (fifth gear needed for sure!) However... the 5th gear seems to be a long way away from 4th in that it really does not provide a lot of ooomph.

              I'll be visiting Watkins Glen and Road Atlanta this coming year, as well as likely Road Atlanta in 2009.. One more data point...
              I might give up a little if I did not have to swap differentials all the time.
              Last edited by M3 Adjuster; 05-31-2008, 05:59 AM.
              Mark Williams
              Dallas, TX

              Nothing says "welcome to the neighborhood" like a search... oh wait... looks like they are all gone! :rastajake:

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              • #8
                for longevity you may want to just use the standard 265.
                1990 e30 m3

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                • #9
                  i have the dogleg with a 3.73 and I track it mostly. I kind of want an even more aggresive rear end (mostly so that I could run a taller tigher like WBSAK03
                  ApexRaceParts.com - Facebook Fan Page - Twitter

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                  • #10
                    Dogleg box with 3.46 LSD Just magic for track and every day use.

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                    • #11
                      hi mark one question can i use 3.73 dif in the city with dog leg?

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                      • #12
                        yes jeanco, it would be a better option than the 4.10 ... I have a friend who has 4.10 and the CR box and the rpms on the way to events are annoying to him... imagine never shifting up from 4th gear with a US box .... he is going to try out a 3.73. As others have indicated, a 3.64 or 3.46 is probably best for a street car that goes to the track.
                        Mark Williams
                        Dallas, TX

                        Nothing says "welcome to the neighborhood" like a search... oh wait... looks like they are all gone! :rastajake:

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                        • #13
                          Definitely dog leg :-)
                          Fritz

                          1987 Hennarot E30 M3

                          http://www.youtube.com/watch?v=J2WsYARLD1Y

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                          • #14
                            dog leg look at the ratios


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                            • #15
                              Dogleg is the only way to go on track. The spacing between 2-3 on the us tranny sucks and 5th is useless. Plus the dog leg sets up the gears in a great H pattern.

                              The shift from 2 to 3 on the us box is like throwing out a boat anchor. With the dogleg it produces a good kick.

                              I remember running TWS backwards with the US box. I would run out of gear in 4th on the US box. Shifting into 5th (overdrive) actually dropped my speed. The car didn't have enough power to overcome the gearing and wind resistance.

                              In my opinion, on 15in tires, a dogleg and 4.10 rear end is perfect for street and DE. Some grannys like to drive around town at 1500 rpms. For those a 3.73 rear and susbscrption to Readers digest would be better choice :wee:

                              For a true race car multiple rear ends is the only way to go. That's another topic though.

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