How To: ATX to MTX swap

[TwIzTeD_3kGt]

This is a write-up I made a long while back for swapping a manual 5-speed in place of an automatic (updated the link in it, free plug for 3sx, hope they don't mind :)). Just adding to the database here:


Well seeing how I just finished my 5-Speed conversion I figured I would make a thread telling what's involved since I couldn't find any when I started:

Here's the specifics of my conversion: I have a 94 SL and put a 5-Speed out of a 93 into it, some of the parts, such as axles, MAY not apply to all years, i'm not sure but it isn't hard to find out.

First, here's the parts you need:

- 5-Speed Transmission
- Flywheel
- Clutch kit
- Shifter (direct replacement) / Shifter cables
- Clutch Pedal (requires drilling a hole through the firewall)
- Clutch Master Cylinder / Fluid Line / Slave Cylinder
- Driver and Passenger Side Axles (for driver side only the inner axle)
- Starter (they ARE different between automatic and manual)

all of these things combined cost me just under $1200, some parts used and some new.

Second, here's the special / hard parts of the conversion:

- Installing the new brake/clutch pedal. Had to take the steering column down, and move the brake booster back to make room to get it in.
- Drilling a hole through the firewall. There isn't much room under there, but it doesn't take a professional.
- Installing the master cylinder. VERY small space to work in, but once it's in there's only one bolt that needs tightening. *The lines must be bled.
- Starting the car when you're done: There's a shift control connector that will be hanging loose, which used to plug into the automatic transmission. Two of the terminals need to be crossed to bypass the neutral safety switch so you can start the car, and two others need to be crossed to have reverse lights. It's different for every year from what i've heard, but it will be the one that has voltage and the terminal directly next to it that need to be connected.

After that, there's not much else other than testing everything out.

Labor Time: With no experience it took me a total of about 10 hours (ran into few problems). If I had to do it again, i'd say it would take from 6 to 8 hours.

Difficulty on a scale of 1-10(hardest): 4 (pretty easy, would have been much easier if I had this thread beforehand)

There are instructions/manuals available for free on the web at: http://www.3sx.com/faq/manuals/

The new 5-speed will require 75W-90 Gear Oil, don't put automatic transmission fluid in it like I almost did.

[Austin@STM]

Thanks for sharing.

[Mike-92RT]

good write up, im sure it will serve a good purpose for people who wanna get rid of the shitty ATX trannys. :)

[n2nsanity]

thanks, was just looking for this :) might be picking up an atx soon and would want to do an eng/trans swap on it if i end up getting it. any problems with the atx ecu? and does the tcu need to be unplugged?
i got carried away on the 5 speed conversion parts. i pulled an ecu and entire wire harness, but forgot all about the smaller brake pedal, lol. also good reminder about the starter. i have a bad 5spd starter and a good atx starter. wonder if the internals or gear could be swapped if that's the only difference? but, i'll probably just buy a new one if i can't get the old one swapped or repaired.

[TwIzTeD_3kGt]

The ATX ECU can stay right where it is, or you can take it out for weight savings. I left it plugged in and had no issues.

[DrGonzo]

Starters internals are different so you can't swap them over. The TCU should be removed or at least unplugged as it does have signals from the ECU going to it.

One thing to remember in doing this type of swap is you loose the functionality of the neutral safety switch. The wiring for the ATX is different so the switch on the clutch pedal will not work. If I remember right the switch is a closed contact which means when you step on the clutch it breaks the connection allowing you to start the car. There is no stock wiring in the ATX car to wire in the stock switch so you will have to be creative.

I just didn't bother to hook mine up. I just had to make sure the car was in neutral when I started it! :)

[n2nsanity]

but switching the wire harness and ecu is one way to resolve the neutral safety switch right? or do you not need both of those?

[TwIzTeD_3kGt]

That should solve it. But it's not "needed", unless you really want a neutral safety switch.

[DrGonzo]

You would have to swap out the ECU/Engine harness, the front interior harness and maybe the front main body harness to get complete functionality.

[n2nsanity]

well, theres not too much more to pull then. if i end up doing a 5spd conversion i'll document it. if not, i'll have some more parts for sale :)

[ElDominio]

Any word on how to make cruise control work??????????

[TwIzTeD_3kGt]

Never did work the cruise control out.

[Dbeltran24]

From my experience the starters are practically the same between an atx and mtx. I currently have a mtx starter in my atx. I've had it in for over a year now with no problems. The gear on the end was the same size and same number of teeth. Bolted right up with no problems. Only thing I saw visually different was the lack of a heat shield on the MTX starter.

[n2nsanity]

i have an extra body wire harness i was pulling apart and tracing wires on. there are 3 connectors by the clutch pedal. the two 2pin connectors which are used and a 4pin connector which isnt used on an mtx. 1 of the 2pin connectors i have traced down. its just a ground on one end and a relay(mb543647) on the other. the other 2pin connector shares 2 wires with unused 4pin connector (which i haven't traced yet). i'm not sure of this yet, but i think the 4pin connector is actually used on an atx. if i'm right, the neutral safety switch deal might be an easy fix providing you already have a mtx ecu, but don't feel like changing an entire harness. i would need to get ahold of an atx body harness for comparison. i think i'll have one soon though.
*also, none of this is solid information yet, just my assumptions so far

[TwIzTeD_3kGt]

From my experience the starters are practically the same between an atx and mtx. I currently have a mtx starter in my atx. I've had it in for over a year now with no problems. The gear on the end was the same size and same number of teeth. Bolted right up with no problems. Only thing I saw visually different was the lack of a heat shield on the MTX starter.

The starters are different between MTX and ATX. There's also a difference between Cali-spec MTX and Fed-spec MTX. An ATX starter will NOT work on a MTX. The pinion gear in the ATX starter does not kick out far enough to reach the flywheel's ring gear. Your situation is the opposite of this, so apparently the MTX pinion gear is long enough that it doesn't kick past the torque converter's ring gear. Good to know. However I would worry about just how much of the pinion gear is actually engaging the ring gear.

[DrGonzo]

From my experience the starters are practically the same between an atx and mtx. I currently have a mtx starter in my atx. I've had it in for over a year now with no problems. The gear on the end was the same size and same number of teeth. Bolted right up with no problems. Only thing I saw visually different was the lack of a heat shield on the MTX starter.

Sorry but that's way wrong!! The ATX and MTX starters are completely different! Yes it will bolt right up and yes it has the same amount of teeth but the kickout on the ATX is further that that of the MTX. So if you are are using an MTX starter on an ATX you are most likely chewing up the teeth on the torque converter as it is not engaging far enough and only mating about half the surface area.

Edit: Ok so I had the two mixed up.... But still the same point is made!

[Hans@GZP]

Geez, I did a write up on this back in 1999 :p

[DrGonzo]

Geez, I did a write up on this back in 1999 :p

So then where is it??? LOL

[TUFFTR]

The starters are different between MTX and ATX. There's also a difference between Cali-spec MTX and Fed-spec MTX. An ATX starter will NOT work on a MTX. The pinion gear in the ATX starter does not kick out far enough to reach the flywheel's ring gear. Your situation is the opposite of this, so apparently the MTX pinion gear is long enough that it doesn't kick past the torque converter's ring gear. Good to know. However I would worry about just how much of the pinion gear is actually engaging the ring gear.


Sorry but that's way wrong!! The ATX and MTX starters are completely different! Yes it will bolt right up and yes it has the same amount of teeth but the kickout on the ATX is further that that of the MTX. So if you are are using an MTX starter on an ATX you are most likely chewing up the teeth on the torque converter as it is not engaging far enough and only mating about half the surface area.

Edit: Ok so I had the two mixed up.... But still the same point is made!

Just to add a bit more. I used an Automatic starter in my manual without any prior knowledge of this issue. I then got a call from the shop who said the car's starter would spin but wouldnt turn the motor. the Automatic starter motor engages the manual flywheel with about 1-2mm of contact. after a while it eventually gave out and chewed up the end of the flywheel.

So again, IT DOES NOT WORK! it will chew out your flywheel! Manual starter must be used!

[Hans@GZP]

So then where is it??? LOL

Maybe the waybackmachine still has it on file from the time I built the stone henge LOL

[Atrosity]

Maybe the waybackmachine still has it on file from the time I built the stone henge LOL

Wow so you are THE Hans in the history books who built stone henge...fuck man, it all just adds up now.

[Assy]

how did you get the reverse light to work and the speedo?

[TUFFTR]

how did you get the reverse light to work and the speedo?

Personally with me, I made my loom a shambles when i did the conversion (also went SOHC to DOHC long story) anyway, reverse lights should still be a wire up the front in the loom SO IVE SEEN TOLD, i couldnt find this but found it running along the RHS drivers footwell. so i found the appropriate 15A power source from the fusebox to the reverse light switch, and from there i installed a wire (all factory looking no random shit everywhere) going to the drivers side footwell.

[TwIzTeD_3kGt]

how did you get the reverse light to work and the speedo?

The speedometer uses the same plug on both transmissions. For the reverse lights, IIRC, there's 2 wires in the harness that used to plug into the ATX that need to go to the reverse switch on the MTX. I believe I cut them out of the ATX plug and connected them to the plug on the MTX.

[n2nsanity]

or u could switch out the entire harness, right?
i'm going to be doing one soon. i grabbed every single part that i could possibly need, lol

[Assy]

do you recall what colors and where i dont know how to test to find it.... also what did you cut to make the car think its in park?

[DrGonzo]

If you are using the ATX harness you will need to bypass the ATX neutral safety switch. I don't know the pins off the top of my head but on the ATX harness in the engine that connected to the Trans you will have to jump two wires together.

[TwIzTeD_3kGt]

do you recall what colors and where i dont know how to test to find it.... also what did you cut to make the car think its in park?

What year are you working on?

[Assy]

its a 93 3000gt thanks

[TwIzTeD_3kGt]

Here's the wiring diagram for that circuit:
http://i39.photobucket.com/albums/e200/twizted_3kgt/ATN-SSw1.jpg
http://i39.photobucket.com/albums/e200/twizted_3kgt/ATN-SSw2.jpg

Note the connectors at the bottom of the first picture and their shapes/sizes. I'm not 100% sure which connector is the one that plugs into the trans, if you can tell me which one it is, I can tell you for sure. But I think it's (B-26), in which case you would need to connect wires 7 (yellow) and 8 (red) for the starter. It looks familiar but it's been a long time since I've dealt with this, so I don't want to send you on a wild goose chase.

Here's those circled so you can see what I'm talking about.
http://i39.photobucket.com/albums/e200/twizted_3kgt/ATN-SSw1-1.jpg

[Assy]

ok so if im reading the diagram right 5 and 2 are for the back up lights?

[n2nsanity]

Hey, can I get more details on the holes in the firewall?
I'm trying to figure out how to drill the big hole for the clutch cylinder.
What tools to use, what method, etc.
The only useful trick i can think of is to use the pedal assembly for a template.

[GTwizard]

That how it done. bolt the peddles up, make your mark, remove peddles, and go to town.

[n2nsanity]

That how it done. bolt the peddles up, make your mark, remove peddles, and go to town.

go to town with what? lol
what can make a nice round 2" hole through metal?

would a hole saw work?
those are meant for wood, i thought

i'm not trying to make a sloppy hole with a jigsaw
don't think there's even room for that anyway

[TUFFTR]

I know this sounds crap, but it worked a freeken treat. On the magna there is like an inner sheet with a hole cut out, but no hole on the firewall, so if you can imagine, from the inside there is a perfect template of where to cut the hole. I took the handle off a file and shapened the end of the handle side up, used it like a giant punch. From under the dash the 14" ling file was huge, so i just let it sit against the inner cutout in the metal, then BAM with a hammer. Repeat all around the hole until the metal basically flops out.

It's barbaric, but there is no room for a holesaw, so I tried this and I'd do it again.

[n2nsanity]

my firewall looks solid on both sides, ill have a closer look tomorrow
also, my dash is out, so that might give me more room
ill find a way, this just seems like the biggest pita of this conversion and noone mentioned how they did it

[TUFFTR]

If the dash is out I'm sure a holesaw would be the quickest way BUT in saying that, That's only a guess, I did mine Dash in.
Good luck dude.

[GTwizard]

No matter what, you will be drilling at an angle. But than use cutting tips/gringing tips or what ever you can find to get the holes to size. I would make an other template from the peddle assembly. One that can be used from the engine compartment. This will help with the final grind and cutting of the holes. Easier to see when not standing on head. Hole saw work on metal, but you don't have the room to use a hole saw that is the correct size. Use a smaller one. The hole will end up obround, than just need a little clean up to make it round. Right angle dril helps and if you get jobber length (short) drills can be done from up top. Remember this is only soft steel. Like way soft. It is not going to be perfect. But it does not need to be. So don't get hung up about it. You are only looking for the 3 Fs.
FIT, FORM and FUNCTION.

[Dbeltran24]

Sorry but that's way wrong!! The ATX and MTX starters are completely different! Yes it will bolt right up and yes it has the same amount of teeth but the kickout on the ATX is further that that of the MTX. So if you are are using an MTX starter on an ATX you are most likely chewing up the teeth on the torque converter as it is not engaging far enough and only mating about half the surface area.

Edit: Ok so I had the two mixed up.... But still the same point is made!

Well S#!t, Did not know this. I'm surprised I've gone a year without issues .... (Starter related issues that is). Needless to say, once I install the other trans I picked up I will be putting in the correct starter.
By the way DrGonzo, I still haven't installed the trans I picked up from you. I've been having issues finding a garage space to work in. I'll let you know how it turns out, whenever I get a chance to finish the job.

[TwIzTeD_3kGt]

I get to do this again in a week or two, should refresh my memory.

[n2nsanity]

Well S#!t, Did not know this. I'm surprised I've gone a year without issues .... (Starter related issues that is). Needless to say, once I install the other trans I picked up I will be putting in the correct starter.
By the way DrGonzo, I still haven't installed the trans I picked up from you. I've been having issues finding a garage space to work in. I'll let you know how it turns out, whenever I get a chance to finish the job.

last 2 starters i replaced i didn't even have to jack up the car lol

[n2nsanity]

didn't have too much time to work with today
firewall looks solid and flat on both ends
got the shifter and old pedal assembly off

can't find but 2 of my old hole saws, of course the wrong sizes
so i picked up a new set along with some stepless bits
gonna give this a shot tomorrow
i need to widen the hole for my battery wire also