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AT to MT swap

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Old 07-23-2008, 12:05 AM
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AT to MT swap

This is not your average conversion thread asking how much it would cost or how to do it, so please keep flames and bullshit out of my thread.

This is the first thread and I am probably the first person (that I am aware of) to post that they have DONE IT.

This is intended for future use of other enthusiasts who may wish to do the swap. I'm not going to give a step by step, but rather a general idea of what is necessary and how to go about it. I will give a few hints and tricks I learned along the way to save money and time for others.

My car was an early build 04 AT with 117,800 on the original engine and a reman trans. I bought it dirt cheap with the intention to convert and mod it at some point. I drove it for over a year as an AT to learn how the car responds and drives, while gathering parts and information for the swap.

I bought almost all the necessary parts for the swap from one single parts car to simplify matters. I had to source a few parts via eBay, other parts sources, and new from Mazda when they were not available used.

Here is the list:

-complete 6 port engine with all external parts, manifolds, injectors, flywheel, and wiring harness (including the wiring that goes from the battery terminal, to fusebox, to starter). Of course I rebuilt the engine before use since I can do so for just a few hundred dollars in parts cost and a few hours of labor.

-6sp trans, I chose to have mine gone through before install to replace the questionable/troublesome 2nd gear synchro

-MT starter (if possible the upgraded/high torque starter is greatly preferred)

-clutch parts (I used stock stuff but you could always buy a new clutch kit instead)

-6sp carbon driveshaft if available, however YOU CAN USE THE AUTO DRIVESHAFT WHICH IS STEEL BUT DIMENSIONALLY IDENTICAL. IT should not have a major impact on driveability or acceleration, if any at all, but it is heavier than the carbon MT shaft.

-clutch slave cylinder, master cylinder, hard line and soft line (I bought a SS braided line for a little over $20 instead of using the stock rubber line)

-shifter assembly, ****, boot, inner trim ring (goes inside the silver trim ring on your console, which will get reused from your automatic)

-clutch and brake pedal assemblies (be sure the clutch pedal comes with the rod that actuates the master cylinder, some people remove them). The pedals I found had the pretty aluminum pads, so I also bought the matching accelerator pedal and dead pedal that also did, but this is completely optional/cosmetic and doesnt have anything to do with the swap itself. From what I could tell the accelerator pedal was identical. Also hope that they leave the switches on the clutch pedal for the starter interlock and cruise switch.

-dual oil cooler assemblies with plumbing. You need both coolers, with mounting brackets, and mounting hardware. Be sure to get the ducts that go between the coolers and bumper. There is a long hard line that goes between the coolers, and the shorter hose between the front of the engine and the passenger cooler is also different and must be obtained. The driver side cooler, and it's plumbing, are technically identical to your stock AT's driver-side-only cooler.

-MT steering wheel (to get rid of the paddles which will be useless)

-MT gauge cluster (for the higher rpm tach, to eliminate the AT warning light, gear indicator, etc.)

-MT PCM. Here is where it gets tricky, read more below about this.

-MT ABS pump from the same car the PCM came from.

---------------------------------------------------------------------------------------------------

Here are some hints and tricks I learned along the way.

PCM/KEY/CAR COMPATIBILITY:

I got the PCM from the MT car but then it wouldn't work with the keys in my AT car, because of the transponder chip in the key. The PCM is programmed to look for a specific key chip, and so the MT PCM was still looking for the keys from the car it came out of. As a result, I was initially unable to start and run the engine using this PCM.

I was able to plug my AT PCM into the MT engine harness and fire it right up using my stock keys. One plug from the MT harness will not fit into the AT PCM, this plug operates the auxiliary ports etc. and are not necessary to start and drive the car so it can be left unplugged temporarily.

The AT and MT cars use different injectors, and as a result I would not take the MT engine (with MT injectors) above about 4000rpm due to the fuel flow differences, or risk engine damage as a result. I was breaking in a fresh engine so this was fine by me regardless.

I went to one dealer tech and he said he could not make the MT PCM work in my car, and was afraid to touch it. HE recommended that I try to obtain the original key(s) and ignition cylinder that matches the MT PCM I got, from the same car. HE said if I did this, I could install it on my car and the PCM would be happy and start up.

I was able to find a dealer tech "with a brain" as some others told me I would need to find at a different dealership. He was able to set up the MT PCM to work in my car, with my existing keys and such. Everything in the car then worked except for TCS and ABS. Even my cruise works, and in fact I don't have a clutch pedal switch for the cruise control installed.

Apparently the MT PCM would not communicate with my AT's original ABS unit, so I tracked down the ABS unit that came from the same car as the MT PCM, hooked it up and it regained ABS/TCS functionality. There is probably a way around this, perhaps my dealer tech didn't know how to program the original ABS unit in my car to communicate with the new PCM for some reason. For me this was the easiest method, but I am sure there are other ways to resolve this issue.

WIRING/CLUTCH PEDAL SWITCHES:

I am still using the AT dash wiring harness and engine-bay wiring harness. The only differences in the dash wiring SHOULD be related to the clutch pedal switches. I found this easy enough to get around...the cruise already works, so no need for wiring up the cruise clutch switch.

For the starter circuit I ran a wire from the ignition switch, to the clutch interlock switch, to the starter trigger terminal. On the end of the ignition switch, find the white wire with blue stripe (at least it was on my car), in a group of about 6 or 7. Probe this terminal with a DMM (grounded elsewhere) to be sure there is 0vdc+ when the key is off, or in the ON position, and then 12vdc+ when the key is turned to START.

Once you have verified this wire is the start trigger, splice onto it and run your new wire down to the clutch interlock switch on the clutch pedal bracket. This will be the switch on the back of the pedal near the firewall. Polarity does not matter, just that one wire goes in and one more comes out. I used a spare fuel injector plug/pigtail since my AT dash harness lacked this connector, one from an older nippondenso square style fuel injector, it went right into place like it was made for it. My ignition start wire goes to one wire on this plug, and the other wire on the plug then gets run through the firewall down to the starter.

ON the starter find the small trigger terminal on the solenoid, the only male blade terminal. Do not use the factory plug for this, run your new wire to it instead. Now your starter circuit is complete, and requires the clutch pedal to be depressed for the engine to start, just like stock. IF you get a no-crank, use your fingers to fully depress the clutch switch manually, and check using the key turned to start.

IF it operates then, that means your clutch pedal is not fully pushing the switch, and you must either adjust or shim the arm on the switch. I had to do this to mine. I checked the extra distance needed to fully depress the switch, which was about the width of my fingertip. I removed the little green plastic stopper from the clutch pedal that pushes against the switch, and taped on a spare nut (from a bolt) onto it, in order to push the switch further, then it worked perfectly.

OTHER MISC INFORMATION:

The steering wheel is a direct bolt on/plug in, you reuse your original airbag. I didn't even need a puller for my wheel, I just removed the big nut and pushed hard side to side on the wheel and it released from the splineshaft/column. BE sure to have your old wheel centered before removing it, so you can re-center your new wheel and not have it sideways while driving down the highway.

The powerplant frame is identical between auto and manual. No need to change.

The exhaust is identical between auto and manual.

The hole and mounting points for the shifter assemblies are identical.

I did not install the VFAD on my car, I simply capped the vacuum nipple on the intake manifold that operates it.

Again, you could technically use the automatic driveshaft (steel, fat, heavier) with the MT conversion, but I used the manual driveshaft (carbon/plastic, skinny, lighter) since I had it. They are dimensionally identical as far as the mounting points and length, including the front yoke/splines.

The hole is already cut in the firewall for the clutch master cylinder, there is a plastic filler plate there that simply pops out. The master cylinder can then slide into place, and the clutch pedal slides onto the MC studs inside the car, and then you use 2 nuts to bolt it together on the firewall. I did have to unplug and remove the trans control module (TCM) for the AT, which is bolted in place of the clutch pedal.

The clutch master gets it's fluid supply from the brake MC, and there is a hose that goes from the clutch MC to the brake MC reservoir. The res. has a casting for the nipple, but it is not present. I took my res. off of my BMC (it disconnects via a locking pin underneath the res.) and drilled a hole into it, then inserted a brass fitting that I could connect the clutch MC hose to. This needs to be done with care, you do not want to develop a leak here which could cost you your brakes and clutch while driving. Alternately you could probably order the MT version of the brake MC reservoir with the nipple already cast in.

The firewall of my AT already had the clips that hold the clutch hard line so it went into place like factory. The mounting studs for the bracket that holds the hard line and soft line to the firewall, near the oil filter, are also present on my car so it was also a bolt up affair like stock. THen it is simply a matter of bleeding and adjusting the clutch pedal via the rod and locknut inside under the dash.

The rearend gearing and LSD appear to be identical, as are the halfshafts.

GAUGE CLUSTER CONCERNS:

The MT gauge cluster plugs directly into the stock AT dash wiring and everything seems to work normally. IT did take a few minutes for my gas gauge to come up to the proper level, it seems to have a buffer that slows it's movement a lot. I did have the presence of mind not to install this before going into the dealer for the PCM programming...because the mileage information on the odometer is stored IN THE CLUSTER. As a result, the MT cluster shows lower mileage than my AT car has on it. Dealers always document mileage during any service, so if I had plugged in the MT cluster before taking it in for service, CARFAX would have picked up a mileage rollback discrepancy which would follow the car for life. To avoid this, I waited until the dealer was done to install it.

I did inquire about programming the mileage of my car into the MT gauge cluster, and was told it would probably not be possible to do. Apparently when a cluster must be replaced, a new one is ordered, and the cluster manufacturer (apparently subcontracted by mazda) asks the mileage that the dealer wants put into it before shipping it out. They will apparently not service used units due to possible legal issues.

BRAKE PEDAL SWITCH:

The automatic uses a long cable that runs from the ignition switch, to the brake pedal switch, to the shifter. I had to remove this cable so I could swap pedals, and so that the ignition cylinder would be unlocked without the auto shifter going back into park. For the time being, I removed the cable from the brake pedal switch/housing, since I was not sure how the switch came off of the pedal bracket because I couldn't see it very well.

Once I got the pedal out and compared it to the MT brake pedal, I discovered that this switch would not install onto my MT pedal. Then after studying it for a while longer, I learned that the AT switch actually comes apart in 2 halves, and the upper half (the electrical part) WILL install onto the MT pedal. So then it was all good, I installed the switch with a simple twist, and it plugged right back into my dash harness like stock. I imagine that the MT car uses the same switch, just without the lower half/housing that the AT adds on. The purpose of this lower housing is to accomodate the cable that runs from the ignition to the shifter, though I admit to having no clue why it needs to run through the brake switch.

Once the switch was plugged in, I did have to adjust pedal height to get it to work properly. This switch controls when your brake lights come on as you touch the pedal, and my lights were stuck ON all the time.

---------------------------------------------------------------------------------------------

That is all I can think of right now. Hopefully this puts to rest some of the bullshit spewed on this forum routinely about AT to MT conversions.

Last edited by RotaryResurrection; 07-28-2008 at 03:56 PM.
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Old 07-23-2008, 12:18 AM
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Sell it and get an auto...
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Old 07-23-2008, 12:25 AM
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I do have a manual-to-auto conversion package for sale cheap, if anyone is interested...
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Old 07-23-2008, 12:31 AM
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wow... simply wow
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Old 07-23-2008, 12:54 AM
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this thread is useless without pics, and RR, you sir, have made my day, because you have accomplished what I didn't, I tried to, but obviously it was a total hell so I just swapped cars

good job sir!
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Old 07-23-2008, 01:01 AM
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Cool.
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Old 07-23-2008, 01:27 AM
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wow, sounds like a heck of a job but very good info for people in the future that want to do the swap
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Old 07-23-2008, 02:16 AM
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Other than the electronics side, it is not bad at all. The wiring is all direct plug and play, save for the clutch switch stuff...it is actually easier than converting an FD rx-7. Now that I know exactly what is what (except for the minor issues I have not yet figured out) I could do the job in a couple of days (plus the engine rebuild time). I actually did this one in a matter of about 4 days, counting my engine build, and I had several distractions in between those 4 days as well.

This will become more popular when the JDM engine packages start coming across, like the 13bREW and 13bt packages do now. The wiring should theoretically be the same on the engine/trans on those cars since it does not come through the firewall, and so it will be easy to get the motor/trans/wiring and drop it in using the existing back half of the drivetrain, and then simply worry about the pedals, electronics, shift hydraulics, etc.
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Old 07-23-2008, 02:18 AM
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Originally Posted by tajabaho1 View Post
this thread is useless without pics,
Pics of what? What I would show you, would look like a bone stock MT car. The only performance mod I have at this time is a K&N drop in panel in the stock airbox.

I do actually have a few pics I snapped of the clutch MC to brake MC hose connection, and a few comparo shots that prove the driveshafts and PPF's are the same. And of course plenty of me building the engine. I'll post them soon.
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Old 07-23-2008, 12:28 PM
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that's too much info for me.

i believe w/e you posted.
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Old 07-23-2008, 01:43 PM
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Another thing to note. I have not posted a step by step idiot's guide to the conversion, and there is a reason for that. Instead, I have posted a general guide and discussion of the fitment of various parts. It is assumed that anyone who would try the swap has a basic to moderate understanding of the workings of most of the systems in a car, and thus will be able to read what I have written and for the most part understand what I am talking about.

Sure, there will be times that you can't envision some technical aspect of something in your head until you've seen it and held it in your hands, but if you don't know the general procedure for removing an engine from a car for example, then you have little to no business trying this swap yourself. That is not to offend anyone, but rather to serve as a reality check and to keep newbs from getting in over their heads. I get a lot of rx-7s brought to me that the owner took apart, overestimating his own abilities, and now doesn't know how to get it back together again.

Please bear this in mind as you read the guide. Think of it as a rite of passage...if you aren't clear on what I am talking about, you need more experience with cars before trying it.
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Old 07-23-2008, 01:49 PM
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Most of the people I think that make threads about doing this swap would pay someone to do it. Would you be able to post the hours spent and a rough estimate of cost? Other than 'SEARCH' the next most common reply is that it 'would cost less taking the hit and trading it in for a MT'. Since you have done it your the best one to ask about costs.
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Old 07-23-2008, 03:10 PM
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Impressive!
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Old 07-23-2008, 03:44 PM
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Originally Posted by expo1 View Post
Most of the people I think that make threads about doing this swap would pay someone to do it. Would you be able to post the hours spent and a rough estimate of cost? Other than 'SEARCH' the next most common reply is that it 'would cost less taking the hit and trading it in for a MT'. Since you have done it your the best one to ask about costs.

I tried to go over that in the writeup. Now of course I am a professional rotary engine builder who has worked on rx7s since 1999 full time, so it's a little different than a regular joe working in his back yard. Also with that said, I do not work in a big shop full of lifts and pits and such, I work with cherry pickers and jackstands in my garage, like like everybody else.

As for cost, I got all of the parts necessary for the swap for around $2500-2800. The engine could have been run as-is, but I of course chose to go through it being that I am a builder and I never trust used engines in my own cars. As such I will not really include rebuild/refresh time and cost.

IF someone were to bring all the parts to me and ask me to do the work for them (the swap alone, not a rebuild) then I would charge them around a grand to do it. Most other rotary shops tend to charge more than that for swaps on rx7s, and would probably charge even more for an rx8 given the new-ness and the fact that they had probably not done the swap before either.

So in theory, if you do it yourself it can be done for under 3 grand, and in about 20 hours at most. The ONLY difficult parts are pulling and reinstalling the engine/trans as a unit out the top, the car is not really made to do it this way (mazda wants you to drop the whole subframe/engine/trans out the bottom, which requires a lift) and also the PCM reprogramming. However if you get more/all of the electronic **** from the donor car (keys, cylinder, immobilizer module, abs module, etc.) then it is possible that this issue could be bypassed and it could become closer to a plug and play.

The next time I have an opportunity, I will try to do it that way and see if it works out any better.
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Old 07-23-2008, 03:49 PM
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Here are some pics. First, the engine build...again not really necessary if you get a good used 6 port engine (or if your 06-08 AT is already 6 port!) but it was a no brainer for me.



















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Old 07-23-2008, 03:50 PM
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Old 07-23-2008, 03:53 PM
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completed engine:







Old auto engine out:







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Old 07-23-2008, 03:56 PM
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dual coolers installed



PPF/DS comparo; auto is the fat shaft, manual is the skinny shaft.





Shots of the brake master cylinder modification for the clutch master, and routing of the new clutch line on the firewall:









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Old 07-23-2008, 04:02 PM
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Completed swap that looks like an oem MT car.







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Old 07-23-2008, 05:42 PM
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Who sleeps in the tent?

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Old 07-23-2008, 05:52 PM
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haha, that is my 4 year old little boy's stuff. he plays over in that area sometimes while I work.
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Old 07-23-2008, 05:54 PM
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you could do this for a business RR - just a thought .
Could be a few AT people on here keen for the swap
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Old 07-23-2008, 06:02 PM
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very cool, thanks for sharing
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Old 07-23-2008, 06:18 PM
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Originally Posted by Brettus View Post
you could do this for a business RR - just a thought .
Could be a few AT people on here keen for the swap
It's something I would have no problem doing, but any necessary PCM programming would have done be done elsewhere obviously. The customer would need to source and bring their own parts for the swap.

I have even done such swaps on rx7s where the customer brings an entire intact partscar, I strip off the necessary parts from it and they haul the shell away. Then they bring their car back a week or 2 later and I pull their original stuff out and put the swap into their car.
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Old 07-23-2008, 06:19 PM
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