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  • #16
    Originally posted by c_w View Post
    Not particularly, it's more in gear times and flexibility. For 0-60 and 0-100 times it's about full throttle power from standing start so as long as the gear spacing isn't widely out it will always be in the power, so to a certain extent gearing doesn't actually make a massive difference (within reason). But shorter gearing just makes the engine so much more flexible, for example from 40mph 4th gear on the road it feels much punchier, and where 3rd felt a bit long out of some corners on track it now feels much better.

    I really didn't like my car on the Ring with the standard diff, felt like I was in 3rd gear for an age, but now just feels "right" yet the drop to 3.46 isn't that big. I put a lower ratio diff in my 205GTi Mi16, a similar drop to what the Coupe has now and it transformed the car - as said it wasn't for out-right acceleration from a stand still but the flexibility the engine had in gear at more varied speeds.

    Granted it's always a balancing act of 2nd too short/3rd too long (as an example) but for me the lower ratio diff suits circuits massively more than the 3.15 diff and on the road the car just feels more lively.
    Not having ever tracked mine but I know what you mean and it's something I would like to do, just not at the top of my list! Coupled with a 6 speed box it's probably a great mod, just need Rage to sort it out cheap for us all.....!
    2002 '52 S54 - Titanium Silver with 18" BBS LMs, AP Racing BBK, KW V3, H&R anti roll bars & ACS flippers (previously 2000 'X' S50 - Arctic Silver)

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    • #17
      This is the email I got back from someone, so there's vat on top of that yet.

      if want the ratio changed in yours inc the cwp and if it does not need bearings looking at £400+vat...if want a full diff supplied with a 3.46 looking from £650+vat all checked etc

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      • #18
        Originally posted by clapshot View Post
        Do you think it's worth getting one built for £650? That seems a lot to me. I could send mine away to the guy and he said he would change it to 3.46 for £400,
        I don't know why but diff work is very expensive, yes it's a pro-job to do due to the setting up of the gears but so aremany things that don't cost this much!

        I bought my 3.46 for £250 off ebay, luckily it was in good condition (as in quiet) though as it was quite old the lsd wasn't very tight; I have recently rebuild the LSD which is quite an easy job easy job, possible to do without remove the diff from the car. On a bench it would be a nice easy saturday afternoon job. Rebuild kits are available from www.driveandtraction.co.uk.

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        • #19
          Originally posted by c_w View Post
          I don't think Exdos thought it wasn't worth it, more the diff he fitted had a slight noise he wasnt happy with and I think that plus him getting the Z4M he just put the factory diff back in.
          Correct. It was my original intention to fit a 3.46 diff and a 6 speed box to my Z3MC. I eventually decided that keeping my Z3MC with OEM diff and gearbox and buying a Z4MC with 3.62 diff and 6 speed box was the better alternative.
          /// Exdos ///
          "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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          • #20
            Well Exdos, buying a diff for £650 doesn't sound too expensive considering the route you took

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            • #21
              Originally posted by c_w View Post
              Not particularly, it's more in gear times and flexibility. For 0-60 and 0-100 times it's about full throttle power from standing start so as long as the gear spacing isn't widely out it will always be in the power, so to a certain extent gearing doesn't actually make a massive difference (within reason). But shorter gearing just makes the engine so much more flexible, for example from 40mph 4th gear on the road it feels much punchier, and where 3rd felt a bit long out of some corners on track it now feels much better.

              I really didn't like my car on the Ring with the standard diff, felt like I was in 3rd gear for an age, but now just feels "right" yet the drop to 3.46 isn't that big. I put a lower ratio diff in my 205GTi Mi16, a similar drop to what the Coupe has now and it transformed the car - as said it wasn't for out-right acceleration from a stand still but the flexibility the engine had in gear at more varied speeds.

              Granted it's always a balancing act of 2nd too short/3rd too long (as an example) but for me the lower ratio diff suits circuits massively more than the 3.15 diff and on the road the car just feels more lively.
              The gears for the MC are VERY long and I agree that using a higher ratio diff doesn't really alter the overall acceleration times. Obviously, a car will accelerate faster in a lower gear than the next higher gear. As I see it, the point of swapping the diff is more a case of being able to use, say, 4th gear at 5,500rpm at the highest part of the torque curve, rather than 3rd gear at around 7500rpm when the torque output has dropped from the peak. A collection of close ratio gears just seems more normal to use than fewer very long gears.
              /// Exdos ///
              "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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              • #22
                Originally posted by clapshot View Post
                Well Exdos, buying a diff for £650 doesn't sound too expensive considering the route you took
                True, but I've now got two different fantastic MCs and I've ended up modding them both!
                Last edited by exdos; 01-03-2013, 11:08 PM.
                /// Exdos ///
                "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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                • #23
                  this thread is worth a read (if you haven't already)


                  http://www.z3mcoupe.com/forum/showthread.php?t=10514

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                  • #24
                    Originally posted by exdos View Post
                    The gears for the MC are VERY long and I agree that using a higher ratio diff doesn't really alter the overall acceleration times. Obviously, a car will accelerate faster in a lower gear than the next higher gear. As I see it, the point of swapping the diff is more a case of being able to use, say, 4th gear at 5,500rpm at the highest part of the torque curve, rather than 3rd gear at around 7500rpm when the torque output has dropped from the peak. A collection of close ratio gears just seems more normal to use than fewer very long gears.

                    Yep, why a 6 speed with a 3.46 or 3.64 would be a pretty good combo and what BMW should have done in the first place. It's a bit like how many newer cars are now coming with 7-speed gearboxes, the top speeds and even the top gear mph/1000rpm aren't necessarily higher, the engine just has more gears to choose from to keep it in power/most efficient.
                    Last edited by c_w; 02-03-2013, 05:43 PM.

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