HOW TO: 6MT to 7AT conversion/swap

CyFi6 · 09-21-2020, 04:18 PM

You read the title correct. I'm pretty sure I am the only one that is every even going to want to do this swap but I figured I would share my experience and research with the 370Z world so anyone else in the future could benefit from the significant amount of time and energy I put into figuring out this swap.

Ive been a die hard manual transmission guy my entire life and have driven mostly manual transmission cars. Was no different when i bought the Z but I never gave the auto a thought. After driving the Z for a while I learned about how good the auto was on the Z and started considering it.

The main things I didnt like about the manual were:
1.Clutch chatters. My Z only had 4k miles when I bought it but its done it since day one. Unless the revs are just right the car would shake/shudder when releasing the clutch. This made it really annoying to drive and seems to be normal. I even upgraded to the RJM pedal which helped massively with pedal feel but didnt change the chatter at all just made it easier to control.

2. Rev hang. Its so difficult to get moving from a stop at the same pace of other drivers because shifting from 1 to 2 you have to sit and wait for the revs to fall.

3. I am just getting tired of manual in general. I wanted to drive this car daily and with a manual I found myself driving my other cars more to avoid dealing with the annoyance of shifting from 1-3. All I do is driving around town so it gets annoying.

I've got enough invested in this car that I didn't want to trade for an auto. I already have stereo upgrades, exhaust, clear bra etc. This vehicle is also the exact year, mileage, color and trim that I wanted. So I decided to do a manual to auto swap and it turned out successful.

There's a bit of wiring involved but the mechanical parts are pretty straightforward.

The main things that need to be swapped:
1. Transmission (obviously)
2. Flexplate/flywheel, bolts etc
3. Shifter assembly
4. Pilot bushing
5. Driveshaft
6. ECU/BCM
7. Transmission cooler needs to be added
8. Paddles (if you want them)
9. Need a donor AT dash harness to grab some connectors and terminals
10. Brake pedal assembly (wider on the AT)

I am attaching a full BOM which includes PN's of everything I bought for this swap. Total was about $3,100. After selling the manual trans I might make back some of that. There are odds and ends that are not on the list but the list makes up 99% of the things purchased. I also 3D printed a couple small parts like the wire harness passthrough plate that goes where the clutch master used to be as well as some plugs for the clutch line to keep debris from getting in there (in case I ever decide to swap the manual back).

Once the mechanical portion is done there is the bigger electrical problem. The dash harness and the engine harness are both different from manual to auto. You will need to build a new harness for the transmission TCM and for the A/T shifter assembly to supplement the wires that are missing from the MT dash and engine harnesses.

You will also want to purchase a SET (all from same vehicle) body control module (BCM), powertrain control module (PCM) and keys. As long as they are all from the same vehicle you will be able to swap everything and be back on the road with minimal programming (still need to program the tire pressure monitoring system to sync with your sensors). You cannot use your existing MT ECU unless you have some major reprogramming done. You also need an ECU/BCM that match otherwise the car wont start due to anti theft.

I did a full pinout and created the harness diagrams for the two harnesses you will need to build. The first one is for connecting the TCM (transmission control module) which is inside the transmission to the vehicle.

The second one is for connecting the AT shifter to the BCM, gauge cluster, IPDM and brake pedal switch.

Now obviously this is not a step by step tutorial since that would require a lot of time and better pictures but if you are going to dive into doing this swap the information provided here will probably get you 90% of the way.

I am happy to report that the new auto trans is working beautifully and no check engine light. The only warning I have is for the tire pressure monitor which will need to be reprogrammed back to the vehicle. I am really enjoying the auto transmission so far and all the work was totally worth it.

These diagrams should work for both vehicles that have and dont have synchrorevmatch functions.

jae35 · 09-21-2020, 06:20 PM

Great work!

sportsman2003 · 09-21-2020, 06:36 PM

Nice write up and great project. I personally would have just traded the car in or sold it and bought an automatic car. I guess I'm lazy. LOL.

rovert · 09-25-2020, 07:51 PM

Nice work Mate, totally get it.
When you have so much work tied up in other already completed mods + the car that you want, even something major like this can be the easier option.
Well Done,
Cheers.

Quicksilvers · 09-27-2020, 08:45 AM

Excellent job nice write up that’s a lot of work but worth it to some how want to go 7AT. The 6MT takes some getting used to. The CSC issue is not livable for most Z enthusiasts though. What clutch kit and flywheel were you running when you had the 6MT?

JARblue · 09-27-2020, 09:13 AM

Blasphemy!!

Just kidding. To each their own. Very nice work. Could have fixed the chatter with a quiet disc clutch setup from Joe at ZSpeed. But if you're just tired of the manual anyway who cares about it's shortcomings. And although I probably would have gone with phunk's MT-to-AT conversion adapter for the BMW DCT instead of using the 7AT from Nissan, I'm guessing this info will help people that want to do either conversion. Thanks for sharing your hard work

TruffleShffle · 10-14-2020, 05:14 PM

This is great!! I am looking to do the opposite, AT to MT, but this information will help me a lot when it comes to the wiring harness. How was the harness work? Was it pretty easy? That's been the only thing I have been dragging my feet on is I'm not looking forward to figuring out what is different between the AT and MT wiring harnesses.

CyFi6 · 10-14-2020, 05:58 PM

Quote:

Originally Posted by TruffleShffle

This is great!! I am looking to do the opposite, AT to MT, but this information will help me a lot when it comes to the wiring harness. How was the harness work? Was it pretty easy? That's been the only thing I have been dragging my feet on is I'm not looking forward to figuring out what is different between the AT and MT wiring harnesses.

Honestly going from MT to AT was probably way harder than doing AT to MT since the AT harnesses have extra wiring. I think the wiring for AT to MT would be relatively straightforward and I am happy to help you figure it out since Im pretty familiar with the trans wiring now.

I think the only wiring you would need to ADD is for the synchro rev match function if you want to have that, but they are only a few extra wires.

09-25-2020, 07:51 PM	#4 (permalink)
rovert Base Member Join Date: Nov 2015 Location: Australia Posts: 64 Drives: 08 Skyline 370GT Rep Power: 10	Nice work Mate, totally get it. When you have so much work tied up in other already completed mods + the car that you want, even something major like this can be the easier option. Well Done, Cheers. __________________ 08 Skyline 370GT SP Coupe 5AT: Diy TT

09-27-2020, 08:45 AM	#5 (permalink)
Quicksilvers A True Z Fanatic Join Date: May 2017 Location: Atlanta, GA Posts: 2,039 Drives: 2017 370z Rep Power: 25463	Excellent job nice write up that’s a lot of work but worth it to some how want to go 7AT. The 6MT takes some getting used to. The CSC issue is not livable for most Z enthusiasts though. What clutch kit and flywheel were you running when you had the 6MT? __________________ Mr. Clean

09-27-2020, 09:13 AM	#6 (permalink)
JARblue A True Z Fanatic Join Date: Mar 2011 Location: Austin, TX Age: 43 Posts: 36,450 Drives: 11 Z34, 98 E36 M3 Rep Power: 2684440	Blasphemy!! Just kidding. To each their own. Very nice work. Could have fixed the chatter with a quiet disc clutch setup from Joe at ZSpeed. But if you're just tired of the manual anyway who cares about it's shortcomings. And although I probably would have gone with phunk's MT-to-AT conversion adapter for the BMW DCT instead of using the 7AT from Nissan, I'm guessing this info will help people that want to do either conversion. Thanks for sharing your hard work __________________ 2011 370Z 6MT Sport Gun Metallic \| ARC \| CJM \| Ecutek \| FI \| Fujimura \| R2C \| SPL \| Stillen \| TWM \| Z1 \| ZSpeed \|

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09-21-2020, 06:20 PM	#2 (permalink)
jae35 Enthusiast Member Join Date: May 2011 Location: Dallas Posts: 278 Drives: 370GT Rep Power: 14	Great work!

09-21-2020, 06:36 PM	#3 (permalink)
sportsman2003 Base Member Join Date: Dec 2018 Location: In the moment Posts: 191 Drives: Sideways most times Rep Power: 11605	Nice write up and great project. I personally would have just traded the car in or sold it and bought an automatic car. I guess I'm lazy. LOL.

10-14-2020, 05:14 PM	#7 (permalink)
TruffleShffle Base Member Join Date: Mar 2018 Location: Phoenix, AZ Posts: 1 Drives: 09 Nissan 370z 7AT Rep Power: 7	This is great!! I am looking to do the opposite, AT to MT, but this information will help me a lot when it comes to the wiring harness. How was the harness work? Was it pretty easy? That's been the only thing I have been dragging my feet on is I'm not looking forward to figuring out what is different between the AT and MT wiring harnesses.