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07-22-2016, 07:38 AM | #1 |
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Swap Your Differential
Just wanted to ad to this subject. The diff swap is a must on these cars, especially if you have a 3.0 with the stock 3.07 gearing. I went to 3.46. It's not as significant as forced induction of course but the torque feels like it's always there with no low points whatsoever. I notice my DSC light coming on more often due to the extra torque.
The gears are closer together and it feels even more like a true sports car. However on the highway i'm still under 3,000 RPM so not a big trade off. If I had to sum up the difference i'd say it makes the car feel lighter overall. I was on the fence about this and now it's the first thing i'd recommend. I spent $500 CDN for the whole job including all new seals and anything replaceable was replaced. DIY would be less than $300. What a DIFFerence it makes in the car. tehehe. Hopefully this helps. Last edited by Sterling Roadster; 07-22-2016 at 08:16 AM.. Reason: Adding |
07-22-2016, 08:16 AM | #2 |
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on the autobahn where cruisingspeeds in excess of 120mph are quite normal for fast cars, you might want to keep that 3.07 ratio. The 330i with same engine even has a longer gearing 2.94. To make it more suitable as a high speed car for the autobahn.
In the US where speeds are really really low (and gas is really cheap) it may be another story. So must is more might
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07-22-2016, 08:18 AM | #3 | |
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07-25-2016, 12:20 PM | #4 |
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I would trade some top speed that I can't make use of for some low end torque.
But something tells me I can't do it on the ///M for $500.
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07-25-2016, 09:35 PM | #5 |
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So, could you elaborate on your "swap"? The what and how of it? Pros and Cons? I've thought of this but waiting to hear from people who actually did it.
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07-25-2016, 10:03 PM | #6 | |
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If you track the car though you need to consider where you run the car, if it's suitable or not.
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07-26-2016, 12:11 AM | #7 |
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Been looking around for the best deal on a 4.10 set for a bit, Tischer lists 33127768526 at $677, although I read on another forum that they might not actually sell for that price. I think that PN is through the Motorsport catalog. ECS lists it for $763 maybe with free shipping too. Will prob snag a set before summer is over
Glad you're enjoying OP, I've read nothing but good things about this upgrade
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07-26-2016, 04:50 AM | #8 |
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I have a full review on my build thread linked in my signature.
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07-26-2016, 05:12 AM | #9 |
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My .02
I had no problem dropping top end speed to get the torque multiplication in the range I typically drive With my 3.91, which is likely too high (numerically) for most I am taching around 3200@80mph The gains at the lower revs are well worth the loss of top end speed as we are limited anyway unless you track your car which I do not. As far as the install goes, it was well in the realm of DIY using jackstands and following all safety precautions. There are lots of vids out there on how to R&R an E46 rear diff.
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08-08-2016, 06:53 PM | #10 | |
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Besides I don't know if i'd bother doing this with an S54, lot's of power and torque already, but I guess you can get used to any amount of power. one day... |
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08-08-2016, 07:34 PM | #11 | |
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Long story short, the shop had a 3.46 diff lying around he was going to sell. I gave him my 3.07 and I took his. Took him a few hours, he replaced all the seals, plugs, fluid and anything that was replaceable for 500 bucks ($380 US) all in. I'm the kind of guy that believes most mods aren't justified financially, but in this case it's the best money I ever spent on a car. Pros: - Car feels lighter with more immediate torque response. - I've read through a few sites that on paper it's supposed to be about 20-30 more pd/ft of torque to the wheels. But on my butt dyno it feels like 40-60. - More shifting though not annoyingly so. - On the highway you'll be closer to the power band in 6th gear so you don't have to downshift to over take someone. Cons: - On the at 120 kmh (70mph) i'm at about 2,900 rpm and before I was at about 2,350. Which to be honest I don't even notice.. And I haven't noticed a decrease in fuel efficiency either. Maybe an extra couple bucks but I don't care. The way I know for a FACT this increases wheel torque: My DSC light very rarely came on when I pushed this car and now it's very often, meaning the sensors are picking up more torque than before. Also with all of the assists turned off, she's much more tail happy. |
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08-08-2016, 07:42 PM | #12 |
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I've never taken my own car to the track but of of curiosity, what are those kinds of restrictions for? I understand noise level and stuff but I know there's some really weird ones.
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08-08-2016, 07:49 PM | #13 | |
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You need to do some calculations to determine the suitability of the different final drives. For example on the M the stock diff is 3.62, with 3.91 and 4.10 as options. I looked at the speed/rpm through the various corners and the fact I was hitting the rev limiter up the back straight in 4th gear. In my case the 4.10 was an easy decision after looking at the data.
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08-08-2016, 07:54 PM | #14 | |
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08-08-2016, 07:55 PM | #15 | |
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A shift would mean getting off the throttle for a moment (that's going to cost me time), and having to downshift to fourth and brake from 125 to 130 to 85 to 90. It's kind of hairy going from those speeds into a that corner and heel toeing badly isn't going to be fun, at those speeds you're seriously going to unsettle the car, and not do the drivetrain or diff any favors! I'm also learning to left foot brake that corner (smoother transition) not something I can do if I've got to downshift from 5th-4th. (*** Pats self on back for pulling that off on 1/3 of laps last weekend*** ) On a different track, the 4.10 might offer some torque advantages and offer a better match for the type of speeds you'd be seeing in corners and between them. On some tracks the speed range for a particular gear might be more optimal with a different ratio. See here and you'll get a better picture. Always trade offs! http://www.bimmerfest.com/forums/sho...60&postcount=1 |
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08-08-2016, 08:03 PM | #16 | |
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I see you're in Kitchener, if you ever need some nice rural back roads, give Goodwood a try. And if you see a moron in a Z4 running through gears like he's in a Le Mans series, it's probably me lol. |
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08-08-2016, 08:09 PM | #17 | |
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08-08-2016, 08:11 PM | #18 | |
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08-08-2016, 08:17 PM | #19 | |
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Give me some road numbers so I can look them up If you ever get West of T.O. give the Hockley Rd a try. It's a great 30 minute or so drive from one end to the other with lots of off camber corners and switch backs. Nice little restaurant in the town of Hockley for a snack and beverage.
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08-09-2016, 02:39 PM | #20 | |
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08-09-2016, 05:43 PM | #21 |
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What am I missing? Every time I have looked it's been around 2k+ for a new diff. Can you do it for less? ~600 is a no brainier!
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