DIY IRS Swap help
Thread Starter
Teching In
Joined: Mar 2014
Posts: 1
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From: Eastern MA
DIY IRS Swap help Hi guys, looking to leverage your considerable brainpower to clarify some things for me. I assure you I've done research and honestly this is the first time I've asked a question here because I usually can find my answer.
I'm putting a 5.3 and M6 into an E46 2000 BMW 323CI coupe. I'll be using my On3 76mm turbo so the rear end isn't going to hold up. Plus I want LSD! This is nothing impossible by any means, I could bolt in an E46 M3 rear end and axle shafts or put a Ford 8.8 in with custom CV shafts. What I'm wondering is how much budget friendliness can be incorporated while remaining worthwhile?
The M3 rear runs about $850 with unknown internals so I'd expect having to rebuild it. The Ford 8.8 is stout, affordable, and has a variety of gear ratios but as far as I know would require custom CV shafts to work. Do you guys see any reasonable alternatives or are these my most budget friendly options? Hopefully I gave you enough information. Thanks for your help!
I'm putting a 5.3 and M6 into an E46 2000 BMW 323CI coupe. I'll be using my On3 76mm turbo so the rear end isn't going to hold up. Plus I want LSD! This is nothing impossible by any means, I could bolt in an E46 M3 rear end and axle shafts or put a Ford 8.8 in with custom CV shafts. What I'm wondering is how much budget friendliness can be incorporated while remaining worthwhile?
The M3 rear runs about $850 with unknown internals so I'd expect having to rebuild it. The Ford 8.8 is stout, affordable, and has a variety of gear ratios but as far as I know would require custom CV shafts to work. Do you guys see any reasonable alternatives or are these my most budget friendly options? Hopefully I gave you enough information. Thanks for your help!
9 Second Club
Joined: Nov 2003
Posts: 13,616
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From: Norn Iron
M3 will obviously be the easiest...but what ratio is the M3 diff ?
If you've access to cheap 8.8" parts, then despite custom shafts or adaptors, long term it might be the better option for you.
If you've access to cheap 8.8" parts, then despite custom shafts or adaptors, long term it might be the better option for you.
yes I know I don't post on here a lot but there's not a lot of info out there on these swaps so I'm going to toss my .02 in. I have a similar swap to what you're talking about. It's an 02' 325i with a forged 370 and a PT7675. I have a 4L80E that I built behind it though rather than a t56 like most do. Made 1K on an SF-902 engine dyno at a little over 14psi on pump 94, so it's pretty real as far as power goes.
I had the same issues as you starting out, the 188mm diff in those cars stock is pretty wimpy. I bit the bullet and bought a complete dropout from an M3. FYI though, I don't know where you're going to find a rear for $850, mine was close to $2500. The lower control arms, sway bar, cradle, brakes and obviously the diff/axles are all different than what currently lives under your car, you're best off buying the whole thing. I needed taller gears (stock M3 is 3.62) so I swapped the gears for 3.15s from an E31, my diff and stubs are also from the E31 since it's a clutch style diff. The BMW fanatics say it's not as good for the track as the stock M-Lock but neither is 1000hp in a 2wd 4 door family car lol. The rear suspension has held up 100% so far, mind you I don't run slicks but I do some stupid nasty high speed burnouts in it and hammer on it all the time. I've put probably 10,000KM on it since I got it running this spring, the whole rear is oem BMW and haven't had a single moment's trouble.
I had the same issues as you starting out, the 188mm diff in those cars stock is pretty wimpy. I bit the bullet and bought a complete dropout from an M3. FYI though, I don't know where you're going to find a rear for $850, mine was close to $2500. The lower control arms, sway bar, cradle, brakes and obviously the diff/axles are all different than what currently lives under your car, you're best off buying the whole thing. I needed taller gears (stock M3 is 3.62) so I swapped the gears for 3.15s from an E31, my diff and stubs are also from the E31 since it's a clutch style diff. The BMW fanatics say it's not as good for the track as the stock M-Lock but neither is 1000hp in a 2wd 4 door family car lol. The rear suspension has held up 100% so far, mind you I don't run slicks but I do some stupid nasty high speed burnouts in it and hammer on it all the time. I've put probably 10,000KM on it since I got it running this spring, the whole rear is oem BMW and haven't had a single moment's trouble.
Last edited by nmccann; Nov 17, 2014 at 06:25 PM.
