M3 diff installed in non-M Z4

No need to change the Drive Shaft from stock to M? Axel sizes, are they the same on the new LSD as the standard Z or will that be any different do you know? Just thinking for wheel alignment etc.

You said about wheel sensors - keep the Z ones but they mount straight on anyways, brakes Eric would only be an upgrade so keep the new set up I guess - another reason to the upgrade the fronts too! :poke: (poke to myself if this goes ahead!)

Having looked around you can pick up a decent looking one for a few hundred pound...

Tell me a little more about the speed differences.
High speed - affected?
Low speed - acceleration etc
Are things really that noticeably changed?

I'm already excited about this but just need pushing over the edge!!
 
Guys, I think these is some misunderstanding here.

The Diff/cradle/trailing arms/etc. are a direct swap. PROVIDED you do the entire swap. You CAN NOT just swap pieces (ex: use M3 diff and Z4 axles). You need the ENTIRE rear end (including brakes). ENTIRE! That means diff/cradle/trailing arms/axles/etc. You can reuse the upper and lower control arms but there is no point. Unless you are changing out bushings, just pull the old Z4 rear end out as a complete unit and install the new M3 rear end as a complete unit.

You WILL need a drive shaft to make this swap work. The non-M Z4s use a 4-bolt flange on the pinion. The Z4M/M3 use a CV joint on the pinion. You CAN convert the Z4M/M3 to a 4 bolt flange and use a 1310 yoke (which is what I did), but you will need the drive shaft cut/welded/balanced to work.

As I tried to make it clear, those of you with a 6 speed are lucky because you can just buy a Z4M drive shaft and use it as is (making it 100% direct swap). It is the correct length and uses the correct CV joint. Those of us with the 5 speed do not have it so lucky since the 5 speed is shorter (therefore needs a longer drive shaft) than the 6 speed.


The overall track width of the M3/Z4M rear axle is 40mm narrower (20mm on each side). I'm currently running 20mm wheel spacers which put the rims back at "stock Z4 width". This is why Z4M rims stick out wider when installed on regular Z4s. This difference in hub width will not affect the ability to align the car, however the reduced track width (resulting from using regular Z4 rims without a spacer) would affect handling. If you want to keep your stock rims, just add 90mm wheel studs (to the rear) and 20mm spacers. Then you will be back at the stock track width.

Personally, the track width issue makes an excellent excuse to upgrade rims. Tell the Misses "Honey, I HAVE to change the rims. As much as I 'hate' to spend the money it's necessary for safety reasons." New rims! :D

Is that clearer?
 
Machine monkey said:
Meto Luke I need to sell more gear knobs now!!
Click to expand...

:lol:
I just put a little plug in your knob thread (just stopped myself from chuckling!)

I think we could get 2 done in 1 weekend :thumbsup:
 
LukeMace said:
Machine monkey said:
Meto Luke I need to sell more gear knobs now!!
Click to expand...

:lol:
I just put a little plug in your knob thread (just stopped myself from chuckling!)

I think we could get 2 done in 1 weekend :thumbsup:
Click to expand...

Certainly doable, especially with 2 people and a lift. :thumbsup:
 
Other Z4 diffs is a cheaper option - the standard 3.0 diff is 3.08 so swapping or a 2.5Si auto diff which is 3.73 would make a big difference to the performance, even if it is still only one wheel drive :D
 
Wondermike said:
Other Z4 diffs is a cheaper option - the standard 3.0 diff is 3.08 so swapping or a 2.5Si auto diff which is 3.73 would make a big difference to the performance, even if it is still only one wheel drive :D
Click to expand...

Yeah, 3.73 is a nice gearing, even if it is one wheel drive :lol:
 
Is the reason for the change just to get a locking diff ?

You could try a quiafe diff from birds auto. A straight swap I think and saves replacing the whole rear end - although possibly more expensive if you use a second hand M3 axle etc.
 
wayne2 said:
Is the reason for the change just to get a locking diff ?

You could try a quiafe diff from birds auto. A straight swap I think and saves replacing the whole rear end - although possibly more expensive if you use a second hand M3 axle etc.
Click to expand...

Cost comparison:

- Second hand (36000 mile) complete M3 rear end with brakes cost me $700

- New qufle/OSI/etc. LSD for Z4 rear end would have cost me $2500-$3000 + install/rebuild

The M3 swap is IMMENSELY cheaper! Personally, spending $2500+ just for a LSD unit is STUPID (when for $1000-$1200 you can pick up an entire rear end).


Not to sound rude, but I don't see how people have an issue grasping this concept. :?

It takes no more work than just installing an LSD in the Z4's stock rear end (since the whole cradle has to come down to get the diff out).

In all actuality, if you had to pay someone to do the swap, arguably the whole rear end swap could come out cheaper in labor than just doing the diff/LSD install (into the Z4 rear end). A mechanic can pull 10 bolts, the entire "old" rear end drops out. The mechanic lifts the "new" rear end into place and installs the 10 bolts. Done.

For me, the LSD is the main reason (3.64 gears were a bonus). BUT, add to it 210mm ring gear vs 188mm ring gear, stronger axles, bigger brakes, etc. (all of which are going to be good insurance with a V8).
 
v8z4 said:
wayne2 said:
Is the reason for the change just to get a locking diff ?

You could try a quiafe diff from birds auto. A straight swap I think and saves replacing the whole rear end - although possibly more expensive if you use a second hand M3 axle etc.
Click to expand...

Cost comparison:

- Second hand (36000 mile) complete M3 rear end with brakes cost me $700

- New qufle/OSI/etc. LSD for Z4 rear end would have cost me $2500-$3000 + install/rebuild

The M3 swap is IMMENSELY cheaper! Personally, spending $2500+ just for a LSD unit is STUPID (when for $1000-$1200 you can pick up an entire rear end).


Not to sound rude, but I don't see how people have an issue grasping this concept. :?

It takes no more work than just installing an LSD in the Z4's stock rear end (since the whole cradle has to come down to get the diff out).

In all actuality, if you had to pay someone to do the swap, arguably the whole rear end swap could come out cheaper in labor than just doing the diff/LSD install (into the Z4 rear end). A mechanic can pull 10 bolts, the entire "old" rear end drops out. The mechanic lifts the "new" rear end into place and installs the 10 bolts. Done.

For me, the LSD is the main reason (3.64 gears were a bonus). BUT, add to it 210mm ring gear vs 188mm ring gear, stronger axles, bigger brakes, etc. (all of which are going to be good insurance with a V8).
Click to expand...

While I agree on most points, a LSD can be had for $1950 from performancegearing.com with no core charge. A few in the E46 community have run their diffs with 400 whp cars, and they've held up well.

Bringing back an earlier topic, I think a turbo is MUCH harder to tune, specifically the partial throttle tuning. With a supercharger, you will always have the same boost at specific rpm, dependent on temperature. Additionally, I've read (but not confirmed) that the the IAT readings are pulled from the MAF sensor on the Z4... and any FI option that utilizes the MAF for IAT has to essentially tune for worst case scenario, thereby limiting power. The MAF is incorporated prior to the compressor, so heat soak has to be accounted for without any kind of feedback. The M54 is detonation limited in most cases, and when you can't measure your limiting factor... well, you're forced to tune extremely rich to keep the engine from destruction.

I agree that a turbo is better in most cases, but not easier. I wouldn't be surprised if a supercharged Z4 shared its alternator bracket with the E46 3-series, reducing production costs. Tuning is still the real killer, and I've only found one tuner (and two shops) that would consider installing a proven turbo kit (Technique Tuning) on the Z4.
 
I thought about at an LSD for #69 as did Wobblewing and a Quaiffe one was around £1300 IIRC from wobblewing's post.

Then I bought an M rear axle. (And the rest of the M to go with it) :D
 
pokeybritches said:
v8z4 said:
wayne2 said:
Is the reason for the change just to get a locking diff ?

You could try a quiafe diff from birds auto. A straight swap I think and saves replacing the whole rear end - although possibly more expensive if you use a second hand M3 axle etc.
Click to expand...

Cost comparison:

- Second hand (36000 mile) complete M3 rear end with brakes cost me $700

- New qufle/OSI/etc. LSD for Z4 rear end would have cost me $2500-$3000 + install/rebuild

The M3 swap is IMMENSELY cheaper! Personally, spending $2500+ just for a LSD unit is STUPID (when for $1000-$1200 you can pick up an entire rear end).


Not to sound rude, but I don't see how people have an issue grasping this concept. :?

It takes no more work than just installing an LSD in the Z4's stock rear end (since the whole cradle has to come down to get the diff out).

In all actuality, if you had to pay someone to do the swap, arguably the whole rear end swap could come out cheaper in labor than just doing the diff/LSD install (into the Z4 rear end). A mechanic can pull 10 bolts, the entire "old" rear end drops out. The mechanic lifts the "new" rear end into place and installs the 10 bolts. Done.

For me, the LSD is the main reason (3.64 gears were a bonus). BUT, add to it 210mm ring gear vs 188mm ring gear, stronger axles, bigger brakes, etc. (all of which are going to be good insurance with a V8).
Click to expand...

While I agree on most points, a LSD can be had for $1950 from performancegearing.com with no core charge. A few in the E46 community have run their diffs with 400 whp cars, and they've held up well.

Bringing back an earlier topic, I think a turbo is MUCH harder to tune, specifically the partial throttle tuning. With a supercharger, you will always have the same boost at specific rpm, dependent on temperature. Additionally, I've read (but not confirmed) that the the IAT readings are pulled from the MAF sensor on the Z4... and any FI option that utilizes the MAF for IAT has to essentially tune for worst case scenario, thereby limiting power. The MAF is incorporated prior to the compressor, so heat soak has to be accounted for without any kind of feedback. The M54 is detonation limited in most cases, and when you can't measure your limiting factor... well, you're forced to tune extremely rich to keep the engine from destruction.

I agree that a turbo is better in most cases, but not easier. I wouldn't be surprised if a supercharged Z4 shared its alternator bracket with the E46 3-series, reducing production costs. Tuning is still the real killer, and I've only found one tuner (and two shops) that would consider installing a proven turbo kit (Technique Tuning) on the Z4.
Click to expand...

$1950 is quite a bit lower than I had found in my digging. Even so, it's still $1000 more than I have into the M3 setup and I got bigger/stronger parts to boot.

My "BMW tuning" experience is ZERO, so I don't know anything about the issues/limitations of tuning the Z4's computer. My experience is with GM ECUs and in those cases, it's very simple to convert to a 2 bar (29.6psi) or 3 bar (44.1psi) MAP (manifold absolute pressure) sensor. At that point, you just tune in speed density (RPM vs MAP, with a temperature correction factor) and go play (very easy to do). All cars use speed density as their "fall back mode" (MAF failure mode), so it is critical to have a good SD tune even if one is going to continue to use the MAF.

The IAT (and MAF) should always be after the compressor, not before. Doing so lets the computer take into account the temperature rise resulting from increased boost pressure. Heat soak (and the need for intercooling) is an issue regardless of the FI system (turbo or supercharger). In most cases, the means of making boost (the compressor drive system) has very little to do with intake air charge. Most heat seems to come simply from the process of compressing the air. I have seen many instances of data which show turbochargers creating lower compressor-exit temps than superchargers (at the same psi output) due to compressor RPM related efficiency.
 
shawna said:
SO you have the whole rear end for a 3.0i?
Click to expand...

Me? I have the whole rear end out of my 2.5i (it will fit into a 3.0i) It is the 3.46 gear, open diff rear end. It has 95mm wheel studs, aluminum diff/cradle mounts, and spherical bearings. It's a nice setup if someone wants to buy it from me.
 
v8z4 said:
$1950 is quite a bit lower than I had found in my digging. Even so, it's still $1000 more than I have into the M3 setup and I got bigger/stronger parts to boot.

My "BMW tuning" experience is ZERO, so I don't know anything about the issues/limitations of tuning the Z4's computer. My experience is with GM ECUs and in those cases, it's very simple to convert to a 2 bar (29.6psi) or 3 bar (44.1psi) MAP (manifold absolute pressure) sensor. At that point, you just tune in speed density (RPM vs MAP, with a temperature correction factor) and go play (very easy to do). All cars use speed density as their "fall back mode" (MAF failure mode), so it is critical to have a good SD tune even if one is going to continue to use the MAF.

The IAT (and MAF) should always be after the compressor, not before. Doing so lets the computer take into account the temperature rise resulting from increased boost pressure. Heat soak (and the need for intercooling) is an issue regardless of the FI system (turbo or supercharger). In most cases, the means of making boost (the compressor drive system) has very little to do with intake air charge. Most heat seems to come simply from the process of compressing the air. I have seen many instances of data which show turbochargers creating lower compressor-exit temps than superchargers (at the same psi output) due to compressor RPM related efficiency.
Click to expand...

The Performance Gearing diff is available at http://www.performancegearing.com/pricing.php. It uses five ceramic-coated friction discs, which has its advantages and disadvantages when compared to the OEM speed-sensing diff.

I'm aware of speed density mode, as I was forced to run it for a short while when my MAF failed. On the Z4, cold starts in SD mode are an absolute pain, and if the O2 sensors aren't fully warmed up, the car will stall or go into limp mode. I think most tuners just dump extra fuel to make up for the unknowns. It's far from ideal. Some Z4M supercharger kits don't utilize a MAF at all, instead going for an Alpha-N setup. I don't know if Alpha-N and speed density are synonymous.

If you're going to use the OEM MAF, it must go before the compressor. Ideally it would go after, but no one does it. I'm assuming the environment in which it would be operating (temperature, pressure, etc.) are beyond its measuring or structural capabilities, but I haven't looked into it enough to know why. Technique Tuning utilizes a Porsche MAF in its setup.
 
pokeybritches said:
v8z4 said:
$1950 is quite a bit lower than I had found in my digging. Even so, it's still $1000 more than I have into the M3 setup and I got bigger/stronger parts to boot.

My "BMW tuning" experience is ZERO, so I don't know anything about the issues/limitations of tuning the Z4's computer. My experience is with GM ECUs and in those cases, it's very simple to convert to a 2 bar (29.6psi) or 3 bar (44.1psi) MAP (manifold absolute pressure) sensor. At that point, you just tune in speed density (RPM vs MAP, with a temperature correction factor) and go play (very easy to do). All cars use speed density as their "fall back mode" (MAF failure mode), so it is critical to have a good SD tune even if one is going to continue to use the MAF.

The IAT (and MAF) should always be after the compressor, not before. Doing so lets the computer take into account the temperature rise resulting from increased boost pressure. Heat soak (and the need for intercooling) is an issue regardless of the FI system (turbo or supercharger). In most cases, the means of making boost (the compressor drive system) has very little to do with intake air charge. Most heat seems to come simply from the process of compressing the air. I have seen many instances of data which show turbochargers creating lower compressor-exit temps than superchargers (at the same psi output) due to compressor RPM related efficiency.
Click to expand...

The Performance Gearing diff is available at http://www.performancegearing.com/pricing.php. It uses five ceramic-coated friction discs, which has its advantages and disadvantages when compared to the OEM speed-sensing diff.

I'm aware of speed density mode, as I was forced to run it for a short while when my MAF failed. On the Z4, cold starts in SD mode are an absolute pain, and if the O2 sensors aren't fully warmed up, the car will stall or go into limp mode. I think most tuners just dump extra fuel to make up for the unknowns. It's far from ideal. Some Z4M supercharger kits don't utilize a MAF at all, instead going for an Alpha-N setup. I don't know if Alpha-N and speed density are synonymous.

If you're going to use the OEM MAF, it must go before the compressor. Ideally it would go after, but no one does it. I'm assuming the environment in which it would be operating (temperature, pressure, etc.) are beyond its measuring or structural capabilities, but I haven't looked into it enough to know why. Technique Tuning utilizes a Porsche MAF in its setup.
Click to expand...

Alpha-N uses RPM-vs-TPS (rather than RPM-vs-MAP) to estimate fuel requirements.

Does the Z4 not have an open loop operating table/operation mode? GM engines starts off in open loop (where it ignores O2s) and runs entirely off of SD and MAF (or just SD if MAF is deleted/unhooked) without feedback loop. A good SD tuned engine will run just as smooth as a MAF tuned engine (if everything is right in the MAP table).

With your point about using the Porsche MAF, I would guess they are sticking the BMW MAF ahead of the compressor in order to avoid maxing out the Hz frequency. I highly doubt it is a structural issue (even 14.7 psi of positive pressure should be well within the structural capabilities of a MAF).
 
Great thread by the way. I totally agree that it is much cheaper to install the rear axle of an M3 than to put a quaife LSD in. I have just been lucky enough to buy a full rear axle off an M3 for £150 and will be fitting it hopefully next month. One question, have you made any mods to your front brakes since the discs and calipers on the M3 rear axle are significantly bigger than the ones on my Z. I imagine this would affect brake balance, but this isn't gonna stop me from doing this mod anyway? Oh, I have the 5 speed gearbox and I think I will look into changing that for the six speed at the same time.

Cheers
 
Alun1976 said:
Great thread by the way. I totally agree that it is much cheaper to install the rear axle of an M3 than to put a quaife LSD in. I have just been lucky enough to buy a full rear axle off an M3 for £150 and will be fitting it hopefully next month. One question, have you made any mods to your front brakes since the discs and calipers on the M3 rear axle are significantly bigger than the ones on my Z. I imagine this would affect brake balance, but this isn't gonna stop me from doing this mod anyway? Oh, I have the 5 speed gearbox and I think I will look into changing that for the six speed at the same time.

Cheers
Click to expand...


Definitely if you can find a 6 speed transmission, do that. It will save you some frustration.

Do you have a drive shaft yet? I have an Z4M drive shaft that I'm trying to get rid of. You will need it to bolt up the 6 speed to the M3 diff.

Currently I'm still using the regular 2.5i front brakes, though I'm looking around for a set of 330i calipers/rotors. I don't notice any issue with the bias, but I'm not tracking the car so it doesn't matter anyways.
 
Yeah I'm defo going to go with the six speed, i imagine its a right pain in the arse modifying existing prop. I will need to source a z4m driveshaft and gear shift mechanism, how much do you want for the z4m prop? I'm not sure how much postage will cost to the UK so it may be cheaper to source locally depending on price of course :wink:

Al
 
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