E46 M3 diff in a non-M Z4

[pokeybritches]

I've been weighing LSD options, and I've seen a few E46 M3 rear ends for sale for less than $1000. My search turned up the same questions I have without any answers:

http://www.zpost.com/forums/showthread.php?t=413275

Assuming I found a "full rear end" including brakes, speed sensors, M3 driveshaft, etc, here are my Z4-specific questions:

1. Will this work? Are there suspension/clearance concerns?

2. Is the driveshaft the same, or will I need to pull one off a Z4M?

3. Will the different speed sensors cause any electrical/software issues?

4. Brake bias considerations?

5. Ballpark labor estimate?

I have a finned 3.64 diff just sitting in the garage, so I could ship it out to have a Wavetrac put in... or sell it and buy a new diff from performancegearing.com

Any input is appreciated!

[vachss]

I recall a few years ago someone on Z4Forum put an M diff in a non-M Z4. I seem the remember that the driveshaft fit, but the entire rear had to be swapped to the M-specific parts (rear subframe, diff, half shafts, hubs, brakes, wheels and rear suspension). Doable, but the grand you might save on the diff vs. a straight Wavetrac or Quaiffe install into a non-M diff seems like its seriously outweighed by all the other parts needed (unless you just happen to have the full rear clip from a Z4M or e46-M3 lying around as a donor).

[psygnosis]

The E46 M3 and the Z4M pretty much use the same diff (save for some vents or fins or something I think)

[epbrown]

Originally Posted by vachss

I recall a few years ago someone on Z4Forum put an M diff in a non-M Z4.

That was Graeme watson (username gwatson) in Scotland, who added an ESS supercharger and swapped in an M3 rear end; he sold the car in 2008 to buy a 1-series but before then it was written up in the UK BMW mags - BMW Car, Performance BMW and Total BMW (Sept 2007 issue).

The process was posted up in the now-defunct Z4um, and I don't thnk he moved to z4-forum. He did swap the entire rear end, but it seemed to be a straight-forward change, iirc.

[pokeybritches]

Thanks for the responses! Sorry to hear the writeup is no longer available. I'm assuming there's a reason only one person has successfully done it, and there aren't quality shops in my area that can sort through issues in the event that I get in over my head on a DIY. I'll try to get in contact with gwatson.

[epbrown]

There are several reasons. One is that he was in Europe where the Alpina S was available to someone that wanted a faster Z4, so not many bothered supercharging. The ESS kit Watson used at the time wasn't available in the US yet, so no need to swap rear ends here. Then the Z4Ms were announced less than a year after he finished the car, and people everywhere wanting a faster Z4 had a factory option.

[pokeybritches]

I received an email response from Mr. Watson, and he said unfortunately he never actually went through with the upgrade, and good luck with the research.

[nadaclue]

I realize this post is a couple month old, but I could swear I had seen a tuner shop online that had done the swap. If you're interested I might still have the link on one of my old laptops, I'll see if I can track it down. From what I remember it was a relatively straightforward bolt in swap if you had the entire rear end.

I'm curious as to what rear you're using now with your VF supercharger? Did you ever install the 3.64 rear into the '03? That's the route I was contemplating, though I'd like to have limited slip.

[pokeybritches]

Originally Posted by nadaclue

I realize this post is a couple month old, but I could swear I had seen a tuner shop online that had done the swap. If you're interested I might still have the link on one of my old laptops, I'll see if I can track it down. From what I remember it was a relatively straightforward bolt in swap if you had the entire rear end.

I'm curious as to what rear you're using now with your VF supercharger? Did you ever install the 3.64 rear into the '03? That's the route I was contemplating, though I'd like to have limited slip.

Long answer to a simple question lol...

I currently have the stock 3.07 rear end on the car, but I still plan to install the 3.64 in the next few months to try out the gearing and bracket my ideal final drive ratio. Work has been crazy lately, which is a good thing. I've been working on the car one day a month tops. The rest of the time the car has sat in storage waiting for its completion.

/rant
That being said, the VF supercharger is installed but not running properly. I think it's a small MAF issue (erratic idle with misfires), but I've had little to no tech support from VF. The instructions that came with the kit were for a Z3 with an older model Vortech that did not have a self contained oil system (required tapping oil lines). Needless to say, I'm very disappointed and have spent countless hours trying to reverse engineer the pile of components they sent. While material quality was good, I've had all kinds of fit and finish issues- mostly small things like hoses that were the wrong length and came into contact with the belts; a wiring harness that included an unnecessary resistor; wires the wrong colors; intake piping that simply doesn't fit ANYWHERE; and the aforementioned oil lines... Lesson learned- don't buy an early generation, low-production kit for your first attempt at a DIY supercharger install when it doesn't even come with instructions necessary for your model car or blower. A full writeup will follow.

I've asked for help twice. The first time I included pictures and asked the same question three times before I got a response... it took 2 weeks to get a response (that was poor advice, and would have cost me hours and hours of extraneous work). The second question hasn't been answered after a week and a half even though I included a thorough description and video.

FYI, I would have had this installed at a shop, but the best price I found was $1500 at a shop I knew nothing about 10 hours away. A place in Atlanta quoted me $2500. I will look to ESS and HPF for my Z4M.

/endrant

[nadaclue]

Wow, that sucks. Thanks for the heads up though, I was ready to call up EAS with my credit card this go round. I honestly can't believe someone would want $2500 to install the kit though, seems really high. Especially since one of the perks of the VF kit is suppose to be that it is easy to install for DIY mechanics as opposed to the ESS kit that has to be put on by a registered/qualified shop. But obviously that isn't holding true if the instructions are non-existent and tech support is a ghost.

I'll be really interested to hear how the 3.64 works for you though, seems like it'd be a cheap upgrade in terms of performance for those of us with the 3.07.

[pokeybritches]

I thought it would be an easy DIY as well. However, if you were to buy the kit I could walk you through all the differences now that I've sort of paved the way on the DIY side. Nothing was overly difficult. The backtracking and figuring out where everything went was the frustrating part. I spent more time just looking at the engine and instructions to figure out my next move than I did actually turning a wrench. I think I will be happy with the final product, but the road to get there took quite a bit more than it should have.

I would not pay $4500 for the kit. With the sale going on now, and the fact that there's someone out there that has made the jump before (me), I would go for it. The 3 series guys all seem happy with their finished products. Expect your car to be down two weeks for the ECU to get to California and back (which you will pay for both ways, despite what the instructions say). If you go for it, shoot me a PM and I'll give you my cell/email to answer any questions you have.

[pokeybritches]

As for the 3.64, I bought it mainly to try out the gearing before throwing down several thousand dollars on a LSD. I paired the supercharger to my high mileage for ease on components- around town it isn't any harder on the car because it's not under boost, but the power is there if I want to redline it. I will add torque through the gearing. With the VF kit, redline is 7000 rpm, which is identical to the non-M coupes, and manual coupes have a 3.46 final drive. If the 3.64 is a little too much I'll opt for a 3.46 when I build my diff. If I think I could use a little more (doubtful), I'll go for a 3.91.

I plan to add a lightweight flywheel and matched clutch, so the revs fall more quickly and I can reduce time between shifts. I hate slamming the car into gear before it's ready.

[tom @ eas]

Originally Posted by nadaclue

Wow, that sucks. Thanks for the heads up though, I was ready to call up EAS with my credit card this go round. I honestly can't believe someone would want $2500 to install the kit though, seems really high. Especially since one of the perks of the VF kit is suppose to be that it is easy to install for DIY mechanics as opposed to the ESS kit that has to be put on by a registered/qualified shop. But obviously that isn't holding true if the instructions are non-existent and tech support is a ghost.

I'll be really interested to hear how the 3.64 works for you though, seems like it'd be a cheap upgrade in terms of performance for those of us with the 3.07.

$2500 is rather steep for installation. Shop around, check the independent shops as well, the kits can typically be installed in a full day.

Originally Posted by pokeybritches

Long answer to a simple question lol...

I currently have the stock 3.07 rear end on the car, but I still plan to install the 3.64 in the next few months to try out the gearing and bracket my ideal final drive ratio. Work has been crazy lately, which is a good thing. I've been working on the car one day a month tops. The rest of the time the car has sat in storage waiting for its completion.

/rant
That being said, the VF supercharger is installed but not running properly. I think it's a small MAF issue (erratic idle with misfires), but I've had little to no tech support from VF. The instructions that came with the kit were for a Z3 with an older model Vortech that did not have a self contained oil system (required tapping oil lines). Needless to say, I'm very disappointed and have spent countless hours trying to reverse engineer the pile of components they sent. While material quality was good, I've had all kinds of fit and finish issues- mostly small things like hoses that were the wrong length and came into contact with the belts; a wiring harness that included an unnecessary resistor; wires the wrong colors; intake piping that simply doesn't fit ANYWHERE; and the aforementioned oil lines... Lesson learned- don't buy an early generation, low-production kit for your first attempt at a DIY supercharger install when it doesn't even come with instructions necessary for your model car or blower. A full writeup will follow.

I've asked for help twice. The first time I included pictures and asked the same question three times before I got a response... it took 2 weeks to get a response (that was poor advice, and would have cost me hours and hours of extraneous work). The second question hasn't been answered after a week and a half even though I included a thorough description and video.

FYI, I would have had this installed at a shop, but the best price I found was $1500 at a shop I knew nothing about 10 hours away. A place in Atlanta quoted me $2500. I will look to ESS and HPF for my Z4M.

/endrant

Sorry to hear that.

We have the VF Supercharger on our Z4M and are back to putting the finishing touches on tuning - now that MFest and Bimmerfest are behind us. Hardware bolted up without a hitch.

If you're having trouble on your end, please feel free to contact us directly.

[pokeybritches]

Update: Got a response today from VF and an apology for the late replay. I will pull the values and codes they've requested.

Update #2: VF sent me a speedy and thorough follow-on response with potential causes and solutions. I'm satisfied and happy with the new attention and support. I'll hold future updates for the supercharger's review thread.