03-22-2017, 02:11 PM | #1 |
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F chassis diff lockdown kit
I got my lockdown kit from here: http://www.n54tech.com/forums/showpo...33&postcount=1 and thought it would be nice to share the info with the community.
Last edited by feuer; 03-22-2017 at 04:27 PM.. Reason: to fix the broken link |
03-22-2017, 03:36 PM | #2 | |
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Either way, what's wrong with the current F chassis diffs (stock and M Performance)? What problem is this "lockdown kit" trying to remedy? I just replaced my stock open differential with a M Performance LSD and wrote a DIY here. Last edited by Polo08816; 03-22-2017 at 03:41 PM.. |
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03-22-2017, 04:11 PM | #3 | |
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03-22-2017, 05:25 PM | #4 |
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I've looked through a few DIY of the "lockdown kit" for other BMW chassis and it seems like it's supposed to make the differential harder to move under power. However, usually differential bushings/mounts are overbuilt.
I checked the condition of my bushings/mounts at 75k miles and they're fine. No significant wear. I'm not having the wheel hop issues at all. Would you be able to provide a bit more information about your car? - Powertrain mods - Drive train configuration - Describe your current LSD - What type of tires do you use |
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03-22-2017, 05:42 PM | #5 | |
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-Afe intake -Wagner 5" IC -catless DP -RWD -open diff -Federal RSR-R tread wear 140 |
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03-22-2017, 05:47 PM | #6 | |
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I wonder if you would be experiencing wheel hop issues with a limited slip rear differential. I'm not convinced that you are experiencing true wheel hop which is a first modal coupling problem between the drivetrain and suspension. I suspect that you're experiencing inner wheel hop which can lead to wheel hop especially considering your powertrain mods. I had this issue at stock power levels with an open rear differential. Out of curiosity, with your powertrain mods, why haven't you considered a limited slip rear differential before going to this differential lockdown kit? Last edited by Polo08816; 03-22-2017 at 06:01 PM.. |
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03-23-2017, 07:56 AM | #7 | |
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03-23-2017, 08:18 AM | #8 | |
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A search for threads dealing with 'wheel hop' show that the first relevant result is buried almost 4 pages in: http://f30.bimmerpost.com/forums/sho...27wheel+hop%27 Maybe Chicken_Joe can comment. However, a cursory look at his signature says that he has a bunch of powertrain modifications, but stock suspension and stock open differential. |
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03-23-2017, 09:13 AM | #9 | |
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03-23-2017, 09:29 AM | #10 |
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03-23-2017, 09:52 AM | #11 |
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03-23-2017, 08:01 PM | #12 |
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IMHO you need an LSD. Staying with open diff and going 'fun' with power is really not ideal. JMHO
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03-24-2017, 03:52 AM | #13 | ||
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A differential lockdown kit is still not going to stop your inner tire fire/inner tire burnout with those powertrain mods. MPSS has been fine for me so far. I may consider Bridgestone RE-71R next time around but those are only 200 tread wear - which is about the lowest I would probably go for a street driven car. OP, you should make an LSD your next mod. With your powertrain mods, you really need it. |
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03-26-2017, 03:24 AM | #14 | |
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03-26-2017, 04:20 AM | #15 | |
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The BMW M Performance LSD is, surprisingly, a good value since you're getting the entire final drive unit without needing to pay a core charge. With the Quaife unit, you'll probably need to send your final drive in because I'm not confident a diff shop will have spare AH3 cores with the 2.81 final drive. |
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03-26-2017, 04:21 AM | #16 |
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Yes, i've got a quaife for my AH3, very happy, and price is similar to the M performance LSD at least in Europe.
You're correct about the different gear ratio, so fitting the m performance LSD would result in higher rpm for same speed/same gear, which can be desirable in some situations, but results in lower fuel economy at least. I'm not sure what the car ECUs would do with that, perhaps works like a charm (likely - changing final drive ratio is common in racing), perhaps not, but it's expensive to find out...
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03-26-2017, 04:25 AM | #17 | |
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The AH3 has the same diff as diesel engines and potentially 330i/328i as well, so it's rather commonplace (in Europe, but no problem sourcing one for Birds in UK to ship you one)
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03-26-2017, 04:32 AM | #18 | |
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Would replacing diff bushings with stronger polyurethane bushings (e.g. Superpro) not be a cheaper way of achieving the same result?
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03-26-2017, 04:45 AM | #19 | |
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Replacing the bushings is not necessarily "cheaper" because the rear differential bushing (not the 2 front bushings) will require you to drop the rear sub-frame. I'm not 100% on the installation procedures for this "lockdown kit". |
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03-26-2017, 08:11 AM | #20 | ||
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03-26-2017, 03:28 PM | #21 | |
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I suppose if I needed 400+ HP, then I'd just save myself the headache and buy an M3. |
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03-26-2017, 03:53 PM | #22 |
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Why do you think that M3 isn't experiencing wheel hop? They have big diff brace for M3 to remedy the issue. The diffs are interchangeable. Subframe is different. You aren't experiencing hop with your existing setup. Great, but there are people that do! Your comments make you sound less informed.
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