bignoselouie 0 Report post Posted January 13, 2010 Gidday, I recently bought a 98 540i. I really wanted a motorsport version but they were out of my price range. The motorsport has a lower ratio rear end and I think the standard 540i is crying out for this. Has anyone done this modification, potentially it could be a nightmare. I would like to know what other things need to be changed as well as the diffhead. Cheers Mark Quote Share this post Link to post Share on other sites
*Glenn* 854 Report post Posted January 13, 2010 (edited) What is the diff ratio now ?? I've not done one of these, but changing the diff ratio may upset ASC, ABS, DME & EGS. You have speed sensors on all wheels and the speedo works of the L/R wheel sensor, not the diff on these models. I would suggest researching a little bit more and get the right information from someone that has done exactly what you intend to do on exactly the same model car as yours, otherwise it could turn to grief on you. There is also an output stage speed sensor in the gearbox and thats what I was more worried about upsetting things. The 540 motor sport diff has a different size pinion flange, so it wont be a straight swap and the car will need to be recoded for the new diff ratio otherwise gear monitoring will be upset. Edited January 13, 2010 by *Glenn* Quote Share this post Link to post Share on other sites
BM WORLD 1283 Report post Posted January 13, 2010 normally these have a 2.93 ratio . glenn i thought the speedo works off one or more of the wheel sensors . i have heard of people swapping out ratios on these . i have a e39 540i and a couple e38 740i diffs , must check what ratio's they are . i am wondering if the gears from a large case diff like a e34 , e32 , e28 , e23, ,e24 will fit into these e39 diff cases they look to be the same size diff head Quote Share this post Link to post Share on other sites
Mike 1 Report post Posted January 13, 2010 I've read that too, that the MSports have a 3.15 diff. I have a feeling that might just be the US market cars though. Do E39 diffs have the same tags on them with the ratio that the E30's do. If so I'll jack mine up sometime and take a look. Quote Share this post Link to post Share on other sites
*Glenn* 854 Report post Posted January 13, 2010 What is the diff ratio now ?? I've not done one of these, but changing the diff ratio may upset ASC, ABS, DME & EGS. You have speed sensors on all wheels and the speedo works of the L/R wheel sensor, not the diff on these models. I would suggest researching a little bit more and get the right information from someone that has done exactly what you intend to do on exactly the same model car as yours, otherwise it could turn to grief on you. There is also an output stage speed sensor in the gearbox and thats what I was more worried about upsetting things. The 540 motor sport diff has a different size pinion flange, so it wont be a straight swap and the car will need to be recoded for the new diff ratio otherwise gear monitoring will/could be upset. Edited (did more research) Quote Share this post Link to post Share on other sites
HELLBM 1557 Report post Posted January 13, 2010 I have a 3.15 from a 2001 M Sport avaliable. E34 and E39 540`s come as standard 2.93 .My 540is has a 3.45LSD at the moment with 2.93 and 3.15LSD`s on standby.If the Packs could be transfered into E39 we would have done it sometime ago. Quote Share this post Link to post Share on other sites
bignoselouie 0 Report post Posted January 14, 2010 (edited) It is 2.93 at the moment. What are the 3.45 's like, it must get off the mark pretty well. If the speedo works off the wheel sensors all good I imagine. Glenn did you need to take the exhaust off to get at the pumpkin? I agree I need to research this properly not to stuff up other things on the car. I may have to post on the uk bimmersport site. I come from a musclecar background and all drivechain stuff was really easy. Edited January 14, 2010 by bignoselouie Quote Share this post Link to post Share on other sites
*Glenn* 854 Report post Posted January 14, 2010 (edited) It is 2.93 at the moment. What are the 3.45 's like, it must get off the mark pretty well. If the speedo works off the wheel sensors all good I imagine. Glenn did you need to take the exhaust off to get at the pumpkin? I agree I need to research this properly not to stuff up other things on the car. I may have to post on the uk bimmersport site Getting the exhaust of in one piece is easy. Whats the build date of your car or Chassis# Model change 09/98 WDS gives different info for pre & aftr 09/98 and I do agree you need to research it more. I have asked around and don't know anyone thats done one. Don't use the US forums for this info though. Edited January 14, 2010 by *Glenn* Quote Share this post Link to post Share on other sites
Mike 1 Report post Posted January 14, 2010 I have a 3.15 from a 2001 M Sport avaliable. E34 and E39 540`s come as standard 2.93 .My 540is has a 3.45LSD at the moment with 2.93 and 3.15LSD`s on standby.If the Packs could be transfered into E39 we would have done it sometime ago. bugger. so whats the solution for LSD in E39 540i? E39 M5 diff? Quaiffe? Car is a bit of a disapointment in that repsect, DSC is such a kill joy but single spinning isnt much fun either Quote Share this post Link to post Share on other sites
