BMW Transmissions on SR20's

[SE-Rawkus]

The gear ratios from the F80 (M3/M4):
1. 4.806
2. 2.593
3. 1.701
4. 1.277
5. 1.000
6. 0.844
7. 0.671

I?m pairing it with a Q45 (3.54) diff.

[RalliartRsX]

So 1st would be useless with a 3.92....or anything shorter than a 3.43 or something. 6 and 7 would be an overdrive regardless. The rest seem to fall in line with the cd009 ratio

[Yellow4g63]

Originally Posted by RalliartRsX

You need to also consider gear ratio. There's a good chance the dct with 7 gears have enough as a different gear spread where going with a 3.9 or similar will literally deem the first 3 gears useless.

Wow that sucks. Now I have to do some gear ratio calculations.

[PoorMans180SX]

Originally Posted by brndck

z33 auto is 3.3 iirc.
if you want taller, y34 is 3.1

also FYI normal 2way LSD does not fit z33 auto diff, since the ring gear is offset compared to manual trans z33 diff. OS Giken does make a LSD that fits z33 auto, but afaik kaaz and most other diff manufacturers do not offer one that fits z33 auto diff.

Nissan Pathfinder rear diffs are 3.13.
Nissan Armada/QX56 rear diffs vary came in 3.36 and 2.94 ratios as well.

[gills]

Or, add 1000 rpm to your engine speed

[Yellow4g63]

E9x M3 DCT Gear Ratios E92 V8

1st - 4.780
2nd - 3.056
3rd - 2.153
4th - 1.678
5th - 1.390
6th - 1.203
7th - 1.000

with a 3.33 auto final drive on 255/40-17 tires

8500RPM 39.77 62.2 88.29 113.28 136.7 158.01 190.08
RPM 1st 2nd 3rd 4th 5th 6th 7th

with the 3.54 same tires
8500RPM 37.41 58.51 83.05 106.56 128.64 148.64 178.81
1st 2nd 3rd 4th 5th 6th 7th

With a 3.13
8500RPM 42.31 66.18 93.93 120.52 145.49 168.11 202.23
1st 2nd 3rd 4th 5th 6th 7th

Can't format it right for the forum

[thom]

Hi guys,

I just finished with this swap which took me maybe more than 1 month since i did everything all alone at my parking spot .

Parts i purchased:

GS6-53DZ gearbox
Pmc gearbox adapter plate + flywheel
Pmc chassis mount shifter
Flex plate from auto sr20
Sachs oem clutch
Gearbox seals

Everything else was custom made by me. ( except the driveshaft)

Process i can say was pretty straight forward but i had some issues ( i still have).

The spot




Adapter plate on . I believe no one has mentioned that now you can't remove starter without having to remove the gearbox.



Gearbox on .





Took me maybe half an hour to align and install it , most difficult part was to put the damn gearbox on the floor jack.



Then when raising it i realized that the gearbox touches the firewall.

Removing it and bang the firewall was not an option so i placed some small pieces of wood between the firewall and the gearbox and started to raise it slowly and carefully .
You could hear the 30 year old metal bend very easily. Didnt really need a lot to be honest.

Also the 2 top gearbox allen bolts took me i don't even now how many hours since there was absolutely no space to put any tool and torque them down.







After that it was time for the gearbox mount which may look super ugly but i believe it does the job.



Ugly also but stiff selector rod. This one i may order it to be cnc cut because i dont believe its welded 100% straight .



For shifter i chose the shortest option that was available because i dont really like those long ones.




For driveshaft i used the original one with adding a 3 bolt flange and i didnt use the bmw rubber coupling. I didnt take a photo of that.

After installing everything and thinking i am done , the real nightmare begins.

Clutch bleeding = impossible.

Clutch would only engage half and gears didnt go in. Pedal would start to feel stiff only after 40% of the total travel.

I then changed the slave cylinder which was new and thought maybe its defective, and also removed the rubber clutch line and made a stainless steel one.

Did manage to bleed the system , no air coming out all, but still the pedal didnt have the best feel.

The last option that did the job( still not 100%) was to adjust the master cylinder rod that goes on the pedal so it pushes a little more fluid on the system.

I believe the problem is the clutch bearing position and clutch is not pushed 100%.

Pmc says to use the 28.5mm but in my situation i think the 33mm position would work better?
I have emailed them but no reply so i dont know.




Anyway today was the first ride which didnt go as planned and i need your opinion- help.

Gearbox makes a terrible sound which i did notice when i first started the car when was on jack stands and thought it will go away when i install the driveshaft etc.

https://www.youtube.com/watch?v=pf_VHvrCMiM

When driving its sounds very bad when decelerating with gear in.

Any help would be appreciated.

*update*

Looks like i'm experiencing harsh gearset rattle on deceleration, and certain RPM's where the engine NVH is at its worst. After doing some research it seems that some people have this issue after installing lightweight single mass flywheels in their bmw's.

I assume having no rubber guibos on the driveshaft , in combination with how rigidly I have the transmission mounted to the chassis is going to cause some unwanted NVH from the GS6-53dz transmission.

Bmw guys suggest changing the fluid , a mix of 75w140 with atf which i wait to be delivered and see how it goes. Also i think to remove the polybush gear mount and put some normal rubber mounts .

Haven't push the car yet since im trying to break in the clutch and figure out these noises but in general gearbox feels amazing. The gear changes are so smooth.

The only issue is that its very short because i have a 4.36 diff. 1st gear is like it doesnt exist , i dont even use it.

I'll put the old 3.9 crown wheel i have next week and i hope it will be better.

[cured13]

any updates on this?

[thom]

At the moment i have given my kazz diff case to a guy to install a 3.69 fd which i bought.

Now it drives on an open 3.9 diff untill the other one is done.

Managed to fix one of my problems which was the clutch bleed and clutch engagement.

Problem was the stock clutch master cylinder which is 5/8 and it needs bigger one.

I made a plate and installed one 3/4 master cylinder from a 90s land rover which costed only 20$.

Pedal feel instantly changed, gears go in much easier and the bleed only took half an hour.

The only thing left is the sound from the driveshaft which i will probably have to go to the guy who made it and see if there something wrong with it.

[cured13]

Originally Posted by thom

Now it drives on an open 3.9 diff untill the other one is done.

Did you have to use ring gear from old auto tranny or just flexplate?
At what RPM's you are at 100km/h with 3.9 dif.
Do you have stock sr20det power level or higher?
Beside noises, how it feels through the gears?

Im very interested in that upgrade.

[thom]

Originally Posted by cured13

Did you have to use ring gear from old auto tranny or just flexplate?
At what RPM's you are at 100km/h with 3.9 dif.
Do you have stock sr20det power level or higher?
Beside noises, how it feels through the gears?

Im very interested in that upgrade.

I bought a flex plate from ebay which yes was from some auto sr20.

With the 3.9 diff i have 109 km/h at 3.000 rpm. Next month i believe i will install the other diff with the 3.69 fd which i believe will be ideal.

Car makes around 300whp.

Beside the noises it feels great but i still dont really like the chassis mount shifter , maybe because its a "street" car.
I will see how it goes and if im not bored i will install an oem bmw shifter with a custom mount to hold it in place .

[Farzam]

Hi, I drive S-chassis and M3's explicitly so this thread is pretty sick lol


I run this mix in my E36/46 M3's transmissions with SMFW's. Redline is good stuff but you don't necessarily *HAVE* to use that brand if you don't want to. Just follow the mix otherwise. Friends and I run this in 200-450whp cars with great success. Most of us are not gentle with our equipment.


Gearing setups I run in my m3's:
ZF 5-speed: I run 3.38 in NA street cars or turbo cars. 3.64 in NA canyon/track stuff. All these cars usually rev to ~7250RPM.
ZF 6-speed: I run 4.10 in my S54 cars alllll day. ~8100RPM redline 300-340whp. Might go a tad longer with an SR though, but i'd probably try a welded 4.08 out to see how it goes lol.


Mileage on these things is irrelevant if it came out of a car that was well maintained and driven properly. They're stout. Service the detent components while it's out though


I highly encourage people who want to go fast to do DCT swaps. My 500whp E90 M3 feels way too fast for the power level, the shifts are so swift and blissful. Sequential-fast shifts with streetable characteristics *chef's kiss*. If you want to drift still, there are ECU systems that allow you to configure CBW (clutch-by-wire) which is pretty nifty. Very tempting tbh. I'd love to have a more purist themed build and then a K-swapped turbo DCT build. Maybe some day. Cool clip one Cool clip two Cool clip three

Bimmer (Bim-ur) is car. Beemer (Beam-ur) is motorbike.

[tuzzio]

Just sucks the gearing ratio(s) are less than desireable for a street car (in my opinion) for a S-chassis R200 diff. Even if you had a Spec R 3.69.

[Farzam]

Originally Posted by tuzzio

Just sucks the gearing ratio(s) are less than desireable for a street car (in my opinion) for a S-chassis R200 diff. Even if you had a Spec R 3.69.

Yeah only overdrive with the 6spd, BMW folk are an odd bunch. It can work with some setups, but definitely not compatible with everything. Will make the car scream, though. 5spd ZF paired with 3.69 would be manageable imo but not ideal for some people. ~70mph@3500RPM in 5th gear isn't the worst. With a 420g 6spd ~70mph@3000RPM, or ~65mph@3000RPM with 4.10 gears.


This is a situation where a Z diff would come in handy, as you can get them with longer ratios (3.357/3.538). I also believe there are some Nissan R200 diffs with 3.538 FD (some NA RB20/25 auto cars) which might not be as easy to find, but ya never know, might be able to get one for a decent price.

[tuzzio]

Thats good info for sure. Its tempting, but in all (unrelated) honesty, when I run out of KA transmissions, my choice of trans is going to be a tremec TKO. One offering has almost identical to factory KA/SR Gearing, and its small / light / easy to remove the bellhousing. I'm lucky to have the resources available for bellhousing modification as well.

[tuzzio]

For anyone interested, I have purchased D9M13N's car and I will be selling his entire SR to ZF swap. I'd like $3,500 + shipping.

[cured13]

does anyone have for sale auto sr20det flexplate?

[Kingtal0n]

Originally Posted by thom

Hi guys,

I just finished with this swap .....
...
GS6-53DZ gearbox
Pmc gearbox adapter plate + flywheel
Pmc chassis mount shifter
Flex plate from auto sr20
Sachs oem clutch
Gearbox seals

Everything else was custom made by me. ( except the driveshaft)

THANK YOU for sharing this incredible swap journey. It is very helpful!

I have a couple of possible suggestions or comments,
1. I notice the sr20 starter is stuck behind the transmission, you mention trans has to come out to remove starter, What if you used some studs instead of bolts? Or some welded nuts inside the adapter plate? So you can thread bolts of a perfect length in or use studs that stick OUT and make removal possible.

2. The noise and vibrations... I have a couple suggestions,
A. Did you measure the pinion angle of the transmission before making the mount? It may need to be moved up about 1/2" or so. I experienced many swaps such as this in the past where people just made a mount without measuring first and it causes vibrations. I wonder if this is a big issue for you without realizing it. Pinion should be equal and opposite of the differential. I think usually IRS 240sx will give like a 2* or 2.5degree at the pinion so that is the angle you need at the transmission. For example i made a mount for my 4l80e that looked fine, but when I measure it finally it was like 3* wayyy too low on the tailshaft. I had to cut the trans tunnel up to make it fit properly and raise the tail of the trans. I also just went through this in a RHD chaser with a 1jz 5speed swap on a friends car. It is deceiving how high the tailshaft needs to go sometimes.
B. You might add some seemingly random rubber components to the mount and chassis. It sounds strange but... look at a toyota transmission crossmember like for a jzs161, 5speed something, they include these weird rubber parts that for years struck me as odd but eventually I realized they must be there to reduce vibration of specific frequency. Just a thought.

3. The driveshaft is a critical component to be not only balanced but in phase as well. You can't just change the end piece on a typical driveshaft without considering the phase, its relationship with both ends. I 'strongly' recommend getting a custom driveshaft made by a place that specializes in single piece custom swap driveshafts.... for example I used a sikky driveshaft in my LS swap and the key is to NEVER CUT IT, if you have to change the end fine, but don't cut anywhere or try and re-balance the shaft, that is where majority of screw ups occur apparently.

Seems like a great option just needs ironing out. I actually Like the super low first because sometimes you need to move the car up a hill or up a ramp or even to push another car into the backyard (sigh...) and that super low gear is PERFECT for towing or pushing heavy stuff around or when u carry a heavy weight in the car.

Thanks again and pls keep us updated!

[tuzzio]

Suppose I should add these just for context and future people doing the swap as I just pulled it out yesterday:

[brndck]

Originally Posted by tuzzio

]

did i miss what clutch and flywheel setup this is?
i'm using the PMC kit and just the sachs clutch plate and cover they recommended

[Om1kron]

Originally Posted by brndck

did i miss what clutch and flywheel setup this is?
i'm using the PMC kit and just the sachs clutch plate and cover they recommended

https://zilvia.net/f/showpost.php?p=...7&postcount=44

[thom]

I would like to make an update on my " project" .

Unfortunately after spending countless hours trying another gearbox , different mounts different gearbox oils and even adding sound deadening in the whole car, i went back to my old sr20 whining gearbox.


My main problem is that the gearset rattle sound coming from this gearbox on decelaration was just too much for a street car. I couldnt enjoy any ride!


After speaking with PMC they gave me zero help and i believe the problem is the balance of the flywheel in combination with the flex plate. I cant think anything else.

Also at the moment pmc have changed the flywheel for this swap and they have the ring gear on as one piece so you dont need to source for a flex plate.

Does this one have different weight and works better ? I will never know!

[brndck]

Originally Posted by thom

I would like to make an update on my " project" .

Unfortunately after spending countless hours trying another gearbox , different mounts different gearbox oils and even adding sound deadening in the whole car, i went back to my old sr20 whining gearbox.


My main problem is that the gearset rattle sound coming from this gearbox on decelaration was just too much for a street car. I couldnt enjoy any ride!


After speaking with PMC they gave me zero help and i believe the problem is the balance of the flywheel in combination with the flex plate. I cant think anything else.

Also at the moment pmc have changed the flywheel for this swap and they have the ring gear on as one piece so you dont need to source for a flex plate.

Does this one have different weight and works better ? I will never know!

did you ever try getting the flex plate and pmc flywheel balanced as a unit?

[thom]

Originally Posted by brndck

did you ever try getting the flex plate and pmc flywheel balanced as a unit?

This is something i never thought of doing to be honest !

Is it possible in a machine shop ?

[brndck]

Originally Posted by thom

This is something i never thought of doing to be honest !

Is it possible in a machine shop ?

yes any machine shop that balances cranks or flywheels should be able to perform this.

i do like that PMC finally revised their flywheel to include the ring gear. Wish that had been an option when i ordered my kit from them.