2JZ in a Z4 Coupe - Custom Project

[dre99gsx]

Some images of the diff cooler. Exits out of some holes behind the original license plate area.

[Dan [Sac]]

Originally Posted by 3GFX

Redneck mathz:

If the stock drivetrain is built for 200,000kms at 325hp. Wouldn't that mean you should get half the life from twice the power?




NOW TURN UP THE BOOST

You did that like my wife does cooking...
"It says 30 minutes at 225F, so I'll just do 15 at 450F"

I go through more pans than ratchets

[Vanne]

Good job mate, that oughta help quite a bit. Extra fluild too.

[dre99gsx]

Just a quick recap on the GS6-37BZ transmission and how it's holding up, as well as the Z4 non-M 3.64 Diff (with a Quaife).

I have no idea how much longer these two will last, but:

- I'm on my 2nd transmission. 1st one lasted ~155 20 minute HPDE sessions before it blew. I am pointing the finger at heat. I've since installed two oil coolers and a pump, keeping it below 230F. Latest transmission is at ~70 20 minute sessions and going.
- I'm on my 4th? diff, this latest one is on ~49 20 minute sessions. Again, added larger oil cooler and pump.

I'm not sure if the cooler fluid will extend the life of these any further, but I'm at 630+whp for all of these events. I do not launch the car.

I think it's safe to say these two can handle 630whp with quite a bit of abuse. I went into this thinking the transmission would be a box of marbles but it's somehow holding the power. Perhaps don't spread this secret because I need spares to exist

The diff is smaller than the Z4M, and I may upgrade the entire rear end at some point. I'm itching to bump this to 700whp soon because why not.

I do wish there was someone else with evidence of power limit on this transmission. Doesn't seem to be much data out there...

[wdb]

Great data, thanks for sharing it.

I imagine that most of the race prepped cars are built for a particular class and don't have the kind of power you do.

[Dr. Minimus]

Long time follower of the build, happy to see it's still running strong.
I realize this was awhile ago, but what inputs besides the crankshaft position sensor did the BMW DME require before the EPS was enabled? I am planning an LS swap for the same model year.
Also, in case the rear differential is still giving you problems Seem legit garage sells a carrier for a Ford 8.8 diff. I assume you have seen this, but just in case.
https://www.seemslegitgarage.com/pro...frame-axle-kit

[dre99gsx]

RPM signal was all that was needed.

I'm saving up my coins for a Z4M rear frame/diff to replace this when ready. Parts alone will be a fraction of the cost of that cool subframe, but thanks for bringing it up. Didn't know there were other options

[dre99gsx]

[amcp]

That's real nice Clark.

[wdb]

What is that -- 3x the horsepower of the N52? Just wow.

[dre99gsx]

UPDATE:

Alright, transmission #2 blown. 4th gear. This time, was coasting through T5 on NJMP thunderbolt. RPMS shot up at part throttle, and box of marbles. Coasted to a stop, towed it in.

Transmission had ~4 years 79 20minutes sessions (let's assume 27 race hours on it). I think it's safe to assume these transmissions will last but the wear is what will tear it apart. The trans fluid never exceeded 240 degF, always on an oil cooler. I changed Motul fluid yearly. Never launched/drifted. I used 4th gear exclusively on most of the tracks.

I can source these for $600-$900. Have to debate if I keep replacing them or move up to T56 or CD009 (or even E46 M3 Getrag). The cost to swap to something more robust will most likely mean more weight, bigger upfront cost, unknown compatibility between 3.0si diff/driveshaft (would probably need to be custom), distance to shifter location, gear ratios... The fact that this Collins swap kit made the 2JZ swap into this Z4 effortlessly was the big attraction.

T56 and 2JZ adaptor kit: $3500+
Custom driveshaft: $1000?
New flywheel/clutch: $1000?
that's roughly 5 Z4 transmissions... lol.

I hear anecdotes that nothing else fits in the transmission tunnel, but I wish I could see evidence of why/where.

[wdb]

Ooops did I jinx you with the 3X HP thing? Grave apologies!

I'm not far from NJMP. I'd love to see the car sometime. Give me a ping.

[Michael9218]

Have you considered a proper motorsports gearbox with straight cut gears and dog ring engagement? There are a couple of options that use the ZF320 case so it’s literally plug and play (Samsonas and GearMotive). I toyed with a GearMotive box, but in the end sold it as I didn’t like how harsh it was. But, they claim to hold over 1,000 hp.

https://gearmotive.com/bmw-dogbox/

[dre99gsx]

Way out of my budget. I'm working on plan B.

I was once told that an M3 transmission wouldn't fit. I don't know where that rumor came from, but the E90 M3's transmission is the GS6-45BZ, slightly less power rating, and it's actually slightly smaller than the GS6-37BZ. But, for some reason, they are still expensive in the used market.

I could have gone E46 M3 transmission (420G), but I don't know about it's power capabilities. I'm certain all of these transmissions will fit in the Z4 tunnel if the 53BZ can fit...

I sourced a 'cheap' GS6-53BZ from a 335i. These have that pilot bearing in the input shaft.

They are rated at 442ft lbs (vs 273 for the GS6-37BZ). I did lost of measurements, and test fitted the transmission. Surprisingly, it fits! Fits in the tunnel. I can even reuse my existing transmission mount.

Here is what I know so far:
- Both dowel pins on the collins kit line up, so this will be secured and aligned correctly
- Two bolt holes on the transmission near the top need to be drilled / oblonged a bit (Easy to do)
- The start of the input shaft splines are nearly identical in location to the start of the splines on the GS6-37BZ, compared to the bellhousing mounting location. This means my current clutch disc/flywheel combo can be resused.
- Well, I still need to purchase a 26 spline 6-puck from clutchmasters, but they sourced me a kit that uses the same flywheel.
- Both transmissions throwout bearing is the same height, and same inner diameter. The large pivot arms ARE different (sightly), so you can't mix/match
- Transmisison is about 1.5" taller (bellhousing to output flange). The output flange is much larger diameter. I will need to get my driveshaft shortened about 1.5" and have the shop weld on the new driveshaft flange. I'm going to attempt to reuse my current Z4 3.0si differential.
- Shift linkages need to be modified (Easy), but the upper shift arm is wider than the GS6-37BZ. I sourced a new one for cheap, but will need to cut/shorten/weld so my shifter sits in the correct location.
- Gear ratios are slightly taller, which is what I was looking for. I get 5mph more in 2nd, 3rd and 4th. 5 gear remains unchanged.
- The pilot bearing pin is 15mm diameter. I sourced a rod from McMaster and will insert it in my current pilot bearing hole. It is a slight press fit, so this will be perfect dual-use adapter.
- I can reuse my clutch slave cylinder, but what remains unknown is if I get the correct engagement/disengagement. I will have to do further measurements. I may have to switch to the 335i slave cylinder as it seems to have a longer rod.

If this trans can't hold up, I'll have to go to plan C: CD009. That's just may not fit at all, and at that point, I may have to lower the power...