Since many of the threads relating to the conversion of an atx car to mtx have been lost in the database problem that occurred last summer, I thought I'd provide some information on that subject now that I've got mine on the road and have only a few details left to have the project fully completed.
I started with a 95 atx that had thrown a rod (loaded, $500 with lots of nearly new parts - fuel pump, plugs, plug wires, alternator, brakes, radiator, etc), a 93 mtx parts car ($400 with literally new tires and battery, almost new clutch, engine mounts, water pump and alternator; engine had spun a rod bearing and the paint was terrible), a 92 engine/trans/subframe that was known good ($200 and needed 60k work done + motor mounts) and about $400 in new parts. [So far, I've recovered over half of that total from various parts sales, so my total cost is in the 3 digits, which is less than the cost of all the new or virtually new parts I have on it.
]
My original plan was to use the mtx computer and the engine & front body wiring from the 93 mtx to make it a 'real' mtx, but I soon discovered that the wiring is different between 93 and 94/95, so I ended up using the atx wiring and doing the required modifications.
Drivetrain
I used the complete front subframe assembly from the 92, including engine, trans, axles, and sway bar, and added the new motor mounts from the 93. I thought about using the 92 non-vaps rack, but chose instead to keep the 95 rack because the plumbing at the rack appears to be slightly different and the electrical connections are signficantly different, and I wasn't motivated to figure out the wiring crossovers. This is a daily driver, so the steering rack differences aren't that significant to me. However, the hose that fits on the back of the ps pump has a longer 'leg' on the end for the 3.2, so it was a very tight fit between the firewall and the pump - a better choice would be to use the mtx hose.
A/C
Many people who have done the atx to mtx conversion have deleted the a/c, but I chose to keep it. You need all the a/c plumbing from the mtx car, since the accumulator/dryer will not fit at the rear of the engine compartment with the engine moved rearward like it is in the mtx cars. Also, you will need the a/c compressor that goes with the accessory drive type you are using - single belt requires an atx compressor, dual belt requires an mtx compressor.
Radiator, overflow tank, battery location
Since the 95 atx car had a virtually new radiator, I chose to keep that and use the atx cooling fans, atx overflow tank, and atx battery location. This works, but it is very tight between some of the a/c components and the cooling fan asm, so I had to rig up some extra rubber cushions to insert a couple of places to hopefully prevent things from wearing on each other. A better plan would be to use the mtx radiator and cooling fan, so everything can be installed in the stock locations. Either battery tray and overflow tank seem to be able to be used equally well. Regardless of which radiator you use, you will need mtx radiator hoses and heater hoses.
Wiring
The dash and front body wiring are different between 92, 93 and 94/95. The R134a a/c system has added a high pressure switch on the system, the alternator connector has changed to a 3-wire setup (although the middle wire is unused) and the wiper motor wiring connectors are significantly changed between 93 and 94. Thus, if you want to minimize wiring changes, use wiring from the same years. Since I have 93 a/c parts and 95 wiring, I have a high pressure switch on the wiring with no place to go - it turns out that the switch is normally closed and as long as you have the switch plugged into the harness, everything will work okay (of course there is no protection from an overcharged system...)
I installed the 3.2 engine wire harness on the 3.0, and kept the atx front body wire harness. To use the atx wiring w/ the mtx setup, I had to add some length to the a/c low pressure switch wiring, since that has moved from the rear to the front of the engine compartment. The low engine oil sensor is on the rear of the mtx pan and front of the atx pan, so that wire needed to be lengthened as well. In both of those cases, I just added the required length and put split flex over it to protect it like the factory wiring - I ran the a/c wiring across the engine under the intake on the passenger side, and the oil sensor line under the pan next to the flywheel. (Note that if you are doing soldering on the wiring, do the soldering before you plug in the connector to the pcm, just to be sure your soldering iron doesn't do something to mess up the pcm.)
Note that because I'm using atx wiring, I needed to use the atx cruise control. This was fine with me, because I prefer the operation of the electronic cruise control, but if its mounted in the stock location it requires eliminating or reorienting the engine roll damper that sits on the transmission end of the engine compartment. I don't have that connected at this time, but I plan to make a new upper bracket to mount the top end of that damper behind the cruise control servo.
Since I am using the atx wiring, I also needed the atx o2 sensors from the 3.2, as they are 4-wire units v. the 3-wire units on the 3.0.
The pcm needs to be convinced that the trans is in park and drive simultaneously (park to allow starting, drive to turn off the 4krpm neutral rev limiter), which is done on the manual lever position sensor - this is described in detail in a post that Phoenix has linked in another thread, (http://www.shospeed.com/pics/ATXtoMTX.pdf) and I will not duplicate all that information here. I simply jumpered the neutral switch portion, so the car will start even without depressing the clutch (I'm old school and think interlocks are stupid) but you could run a pair of wires from that to the clutch interlock switch if you so desired. I ran a pair of wires to the reverse switch on the transmission, and simply jumpered the two points to tell the pcm that the car is always in drive. (Note that if you ran a couple of wires to a manual switch, I think you could open that switch to allow you to run all the diagnostic tests on the pcm, with it jumpered you cannot run the koer test which requires nuetral.) I drilled a couple of holes in the plastic wiper arm to run the reverse switch wires through, so that when I was all done I could reassemble the manual lever position sensor and it was all sealed up again. This all sits on top of the trans under the air intake hose, so nothing looks out of place unless you really look for it.
As noted by others, the lack of response from the missing automatic transmission causes the pcm to flash the "OD Off" light on the instrument cluster. The OD Off light is part of a module in the center of the cluster - I simply clipped the orange wire going to that module rather than disassembling the entire cluster to pull the bulb. You could alternatively disconnect the connector to that module - doing this also eliminates the "low coolant" light, which I did not want to do.
As others have described, the "Check Engine" light will eventually come on due to the egr system not functioning properly, if you remove the egr as part of the conversion. I used the atx intake (because it was the best looking one I had), so I mounted all the control stuff for the egr system, and plan to connect the egr valve also, just not to the exhaust manifold (since I have 3.0 manifolds on the engine, they are not plumbed for egr). Right now I have a blocking plate over the egr mounting holes on the intake. I will just rig some type of air filter device for the end of the egr pipe that should go to the manifold, and that should allow enough air to flow in the egr circuit to avoid having the CEL come on. Currently, w/ no egr, the CEL will come on after some 2-10 minutes of driving, and then stay on as long as the engine is on. Alternatively, you could pull out that bulb from the cluster, but then you would never see the CEL, even if it should be on.
The default is for autolock to be on, which occurs if the pcm senses someone in the driver's seat and the reverse lights go on and then off. Since that is not desireable on the stick cars, and since my keypad isn't working right, I disconnected the wiring to the seat switch, so the pcm never senses a driver. From my research, it appears this seat switch serves no other useful function, so nothing was compromised by disconnecting it.
Control Cables
Since I used the atx intake, I was able to use the atx throttle cable. (The mounting for the throttle cable and cruise cable to the throttle body are different between atx and mtx.) I also used the atx speedometer cable - the speedo cable has a 'main' section that goes through the firewall to the cluster. The atx and mtx have unique lower portions of the speedo cable, so I separated the main section from the atx lower and plugged it into the mtx lower.
Interior
On the atx shifter, in addition to the trans shifter cable there is an interlock cable that will allow/prevent the key from being turned to the 'lock' position so the key may be removed, and optionally, a vacuum connection that will automatically release the parking brake when the trans is shifted out of park. The vacuum lines to the park brake should simply be removed, and the tap on the vacuum distribution manifold under the hood needs to be plugged - this will ensure that the park brake will not release unintentionally. The shifter interlock cable may simply be disconnected, since the default position allows the key to be removed, so with the cable disconnected the key can be turned to "lock" and removed at any time. The only way that I've discovered to easily remove the atx shifter cable is to cut it and pull it into the engine compartment, since there is a clamp located on the floor of the passenger compartment, under the heat distribution manifold (that is exceedingly difficult to get off) that must be removed to pull out the shifter cable intact.
You need the clutch and brake pedal assemblies from the mtx car - you simply unbolt the atx brake pedal asm and install the mtx brake pedal asm and then the clutch pedal asm. There already is a hole in the firewall for the clutch cable to pass through (its the same one the park brake release vacuum line runs through, if you have that), so you just remove the rubber grommet that is in that hole and use the grommet on your clutch cable to seal the hole back up. This is only difficult because of how hard it is to get under the dash to do the work, and because of all the sharp edges that are under there to cut your fingers while you do it. Removing the knee bolster etc. from the bottom of the steering column helps that task significantly.
While you need to cut a hole in the floor for the shifter to come through and drill 4 holes to mount it, Ford was kind enough to provide dimples in the floor pan marking where the 4 bolts go. So, I just drilled those 4 holes and then laid the plate down w/ the bolts through those holes and marked where the large opening needed to be, then cut that larger opening w/ a Dremel. (The atx cars have a sticky rubber/asphalt-type vibration damper on top of the tunnel in that location, so you may only see the dimples for the rear holes until you scrape away some of that damper material.) The big part of the console is identical between atx and mtx, so only the insert piece that goes by the shifter is different. I saved the console from my parts car and used it, but others have made the atx console work with the mtx shifter with a little creativity. The wiring that was connected to the atx shifter is simply left disconnected inside the console, although you will want to make sure its tied in place so it doesn't rattle.
Exhaust
You need the resonator and pipe from the mtx, since the atx pipe interferes with the shifter, and is too short anyway. I cut the atx pipe right behind the resonator and took the mtx pipe apart at the clamp joint behind the resonator. Then I bought a piece of 2.25" exhaust tubing to patch it. The expanded end of the 2.25" pipe slipped over the pipe to the mufflers perfectly, but the other end was too big to fit properly on the mtx resonator pipe. I made a sleeve from another piece of exhaust tubing which made it all fit snugly, then clamped it together. If you have an aversion to exhaust clamps, it can certainly be welded together, which I may yet do.
Suspension
After removing some 200 lbs from the front of the car, the front end sits nearly 1" higher than before. This is problematic, since many of the atx cars sit too high in the front anyway, so I still need to cut down or change the front springs to get the ride height where it should be. Since I have the typical 'clunk' that indicates bad strut mounts, I'll get some new strut assemblies with the 'right' springs.
I changed the front radius arm bushings to the black ones from Energy Suspension, and they seem to be a big improvement over stock (at least so far). I also put in aluminum subframe bushings, but with a twist from what I've seen done before. I made some isolators from .030" 'paper' gasket material and placed those in every location where steel and aluminum would otherwise meet. This should eliminate the risk of galvanic corrosion and have the side effect of at least a little damping of high frequency vibrations that would otherwise be transmitted from the subframe into the unibody. The gasket material should not creep, so the bolts should stay tight. I also installed 96+ brakes on the front of the car to improve braking performance, and when I have the rear struts off I plan to install a 26mm rear bar.
Results
The aluminum subframe bushings do result in an increase in NVH. Noise transmission from the engine to the cabin is increased noticably for engine speeds above 3500 rpm. While vibration is not really increased, the harshness of the engine noise is increased significantly. Even the shudder from the a/c compressor kicking on is much more apparent. While cruising, the NVH is very comparable to the rubber bushing setup. Overall, for a daily driver its questionable whether it was a good move or not, imho.
I've got nearly 1000 miles on it after the swap and all is working as it should. Once I get the struts changed to eliminate the 'clunk' that currently accompanies every hard bump in the road, it should be good for many more miles. If you have never had the opportunity to compare the mtx and atx side by side, the mtx definitely is quicker and more nimble. And, it seems to be getting significantly better mileage - over 25 compared to around 22 for the type of driving I've been doing.
Here is a photo of the car w/ the stock atx front springs after the installation of the mtx assembly:
Here is a photo of the rod bearings I took out of my "new" engine when I changed them. These are from a reportedly 130k mile engine, but may not have been the originals:
Here are a couple of random photos of the dead 3.2 coming out of the car:
I started with a 95 atx that had thrown a rod (loaded, $500 with lots of nearly new parts - fuel pump, plugs, plug wires, alternator, brakes, radiator, etc), a 93 mtx parts car ($400 with literally new tires and battery, almost new clutch, engine mounts, water pump and alternator; engine had spun a rod bearing and the paint was terrible), a 92 engine/trans/subframe that was known good ($200 and needed 60k work done + motor mounts) and about $400 in new parts. [So far, I've recovered over half of that total from various parts sales, so my total cost is in the 3 digits, which is less than the cost of all the new or virtually new parts I have on it.
]My original plan was to use the mtx computer and the engine & front body wiring from the 93 mtx to make it a 'real' mtx, but I soon discovered that the wiring is different between 93 and 94/95, so I ended up using the atx wiring and doing the required modifications.
Drivetrain
I used the complete front subframe assembly from the 92, including engine, trans, axles, and sway bar, and added the new motor mounts from the 93. I thought about using the 92 non-vaps rack, but chose instead to keep the 95 rack because the plumbing at the rack appears to be slightly different and the electrical connections are signficantly different, and I wasn't motivated to figure out the wiring crossovers. This is a daily driver, so the steering rack differences aren't that significant to me. However, the hose that fits on the back of the ps pump has a longer 'leg' on the end for the 3.2, so it was a very tight fit between the firewall and the pump - a better choice would be to use the mtx hose.
A/C
Many people who have done the atx to mtx conversion have deleted the a/c, but I chose to keep it. You need all the a/c plumbing from the mtx car, since the accumulator/dryer will not fit at the rear of the engine compartment with the engine moved rearward like it is in the mtx cars. Also, you will need the a/c compressor that goes with the accessory drive type you are using - single belt requires an atx compressor, dual belt requires an mtx compressor.
Radiator, overflow tank, battery location
Since the 95 atx car had a virtually new radiator, I chose to keep that and use the atx cooling fans, atx overflow tank, and atx battery location. This works, but it is very tight between some of the a/c components and the cooling fan asm, so I had to rig up some extra rubber cushions to insert a couple of places to hopefully prevent things from wearing on each other. A better plan would be to use the mtx radiator and cooling fan, so everything can be installed in the stock locations. Either battery tray and overflow tank seem to be able to be used equally well. Regardless of which radiator you use, you will need mtx radiator hoses and heater hoses.
Wiring
The dash and front body wiring are different between 92, 93 and 94/95. The R134a a/c system has added a high pressure switch on the system, the alternator connector has changed to a 3-wire setup (although the middle wire is unused) and the wiper motor wiring connectors are significantly changed between 93 and 94. Thus, if you want to minimize wiring changes, use wiring from the same years. Since I have 93 a/c parts and 95 wiring, I have a high pressure switch on the wiring with no place to go - it turns out that the switch is normally closed and as long as you have the switch plugged into the harness, everything will work okay (of course there is no protection from an overcharged system...)
I installed the 3.2 engine wire harness on the 3.0, and kept the atx front body wire harness. To use the atx wiring w/ the mtx setup, I had to add some length to the a/c low pressure switch wiring, since that has moved from the rear to the front of the engine compartment. The low engine oil sensor is on the rear of the mtx pan and front of the atx pan, so that wire needed to be lengthened as well. In both of those cases, I just added the required length and put split flex over it to protect it like the factory wiring - I ran the a/c wiring across the engine under the intake on the passenger side, and the oil sensor line under the pan next to the flywheel. (Note that if you are doing soldering on the wiring, do the soldering before you plug in the connector to the pcm, just to be sure your soldering iron doesn't do something to mess up the pcm.)
Note that because I'm using atx wiring, I needed to use the atx cruise control. This was fine with me, because I prefer the operation of the electronic cruise control, but if its mounted in the stock location it requires eliminating or reorienting the engine roll damper that sits on the transmission end of the engine compartment. I don't have that connected at this time, but I plan to make a new upper bracket to mount the top end of that damper behind the cruise control servo.
Since I am using the atx wiring, I also needed the atx o2 sensors from the 3.2, as they are 4-wire units v. the 3-wire units on the 3.0.
The pcm needs to be convinced that the trans is in park and drive simultaneously (park to allow starting, drive to turn off the 4krpm neutral rev limiter), which is done on the manual lever position sensor - this is described in detail in a post that Phoenix has linked in another thread, (http://www.shospeed.com/pics/ATXtoMTX.pdf) and I will not duplicate all that information here. I simply jumpered the neutral switch portion, so the car will start even without depressing the clutch (I'm old school and think interlocks are stupid) but you could run a pair of wires from that to the clutch interlock switch if you so desired. I ran a pair of wires to the reverse switch on the transmission, and simply jumpered the two points to tell the pcm that the car is always in drive. (Note that if you ran a couple of wires to a manual switch, I think you could open that switch to allow you to run all the diagnostic tests on the pcm, with it jumpered you cannot run the koer test which requires nuetral.) I drilled a couple of holes in the plastic wiper arm to run the reverse switch wires through, so that when I was all done I could reassemble the manual lever position sensor and it was all sealed up again. This all sits on top of the trans under the air intake hose, so nothing looks out of place unless you really look for it.
As noted by others, the lack of response from the missing automatic transmission causes the pcm to flash the "OD Off" light on the instrument cluster. The OD Off light is part of a module in the center of the cluster - I simply clipped the orange wire going to that module rather than disassembling the entire cluster to pull the bulb. You could alternatively disconnect the connector to that module - doing this also eliminates the "low coolant" light, which I did not want to do.
As others have described, the "Check Engine" light will eventually come on due to the egr system not functioning properly, if you remove the egr as part of the conversion. I used the atx intake (because it was the best looking one I had), so I mounted all the control stuff for the egr system, and plan to connect the egr valve also, just not to the exhaust manifold (since I have 3.0 manifolds on the engine, they are not plumbed for egr). Right now I have a blocking plate over the egr mounting holes on the intake. I will just rig some type of air filter device for the end of the egr pipe that should go to the manifold, and that should allow enough air to flow in the egr circuit to avoid having the CEL come on. Currently, w/ no egr, the CEL will come on after some 2-10 minutes of driving, and then stay on as long as the engine is on. Alternatively, you could pull out that bulb from the cluster, but then you would never see the CEL, even if it should be on.
The default is for autolock to be on, which occurs if the pcm senses someone in the driver's seat and the reverse lights go on and then off. Since that is not desireable on the stick cars, and since my keypad isn't working right, I disconnected the wiring to the seat switch, so the pcm never senses a driver. From my research, it appears this seat switch serves no other useful function, so nothing was compromised by disconnecting it.
Control Cables
Since I used the atx intake, I was able to use the atx throttle cable. (The mounting for the throttle cable and cruise cable to the throttle body are different between atx and mtx.) I also used the atx speedometer cable - the speedo cable has a 'main' section that goes through the firewall to the cluster. The atx and mtx have unique lower portions of the speedo cable, so I separated the main section from the atx lower and plugged it into the mtx lower.
Interior
On the atx shifter, in addition to the trans shifter cable there is an interlock cable that will allow/prevent the key from being turned to the 'lock' position so the key may be removed, and optionally, a vacuum connection that will automatically release the parking brake when the trans is shifted out of park. The vacuum lines to the park brake should simply be removed, and the tap on the vacuum distribution manifold under the hood needs to be plugged - this will ensure that the park brake will not release unintentionally. The shifter interlock cable may simply be disconnected, since the default position allows the key to be removed, so with the cable disconnected the key can be turned to "lock" and removed at any time. The only way that I've discovered to easily remove the atx shifter cable is to cut it and pull it into the engine compartment, since there is a clamp located on the floor of the passenger compartment, under the heat distribution manifold (that is exceedingly difficult to get off) that must be removed to pull out the shifter cable intact.
You need the clutch and brake pedal assemblies from the mtx car - you simply unbolt the atx brake pedal asm and install the mtx brake pedal asm and then the clutch pedal asm. There already is a hole in the firewall for the clutch cable to pass through (its the same one the park brake release vacuum line runs through, if you have that), so you just remove the rubber grommet that is in that hole and use the grommet on your clutch cable to seal the hole back up. This is only difficult because of how hard it is to get under the dash to do the work, and because of all the sharp edges that are under there to cut your fingers while you do it. Removing the knee bolster etc. from the bottom of the steering column helps that task significantly.
While you need to cut a hole in the floor for the shifter to come through and drill 4 holes to mount it, Ford was kind enough to provide dimples in the floor pan marking where the 4 bolts go. So, I just drilled those 4 holes and then laid the plate down w/ the bolts through those holes and marked where the large opening needed to be, then cut that larger opening w/ a Dremel. (The atx cars have a sticky rubber/asphalt-type vibration damper on top of the tunnel in that location, so you may only see the dimples for the rear holes until you scrape away some of that damper material.) The big part of the console is identical between atx and mtx, so only the insert piece that goes by the shifter is different. I saved the console from my parts car and used it, but others have made the atx console work with the mtx shifter with a little creativity. The wiring that was connected to the atx shifter is simply left disconnected inside the console, although you will want to make sure its tied in place so it doesn't rattle.
Exhaust
You need the resonator and pipe from the mtx, since the atx pipe interferes with the shifter, and is too short anyway. I cut the atx pipe right behind the resonator and took the mtx pipe apart at the clamp joint behind the resonator. Then I bought a piece of 2.25" exhaust tubing to patch it. The expanded end of the 2.25" pipe slipped over the pipe to the mufflers perfectly, but the other end was too big to fit properly on the mtx resonator pipe. I made a sleeve from another piece of exhaust tubing which made it all fit snugly, then clamped it together. If you have an aversion to exhaust clamps, it can certainly be welded together, which I may yet do.
Suspension
After removing some 200 lbs from the front of the car, the front end sits nearly 1" higher than before. This is problematic, since many of the atx cars sit too high in the front anyway, so I still need to cut down or change the front springs to get the ride height where it should be. Since I have the typical 'clunk' that indicates bad strut mounts, I'll get some new strut assemblies with the 'right' springs.
I changed the front radius arm bushings to the black ones from Energy Suspension, and they seem to be a big improvement over stock (at least so far). I also put in aluminum subframe bushings, but with a twist from what I've seen done before. I made some isolators from .030" 'paper' gasket material and placed those in every location where steel and aluminum would otherwise meet. This should eliminate the risk of galvanic corrosion and have the side effect of at least a little damping of high frequency vibrations that would otherwise be transmitted from the subframe into the unibody. The gasket material should not creep, so the bolts should stay tight. I also installed 96+ brakes on the front of the car to improve braking performance, and when I have the rear struts off I plan to install a 26mm rear bar.
Results
The aluminum subframe bushings do result in an increase in NVH. Noise transmission from the engine to the cabin is increased noticably for engine speeds above 3500 rpm. While vibration is not really increased, the harshness of the engine noise is increased significantly. Even the shudder from the a/c compressor kicking on is much more apparent. While cruising, the NVH is very comparable to the rubber bushing setup. Overall, for a daily driver its questionable whether it was a good move or not, imho.
I've got nearly 1000 miles on it after the swap and all is working as it should. Once I get the struts changed to eliminate the 'clunk' that currently accompanies every hard bump in the road, it should be good for many more miles. If you have never had the opportunity to compare the mtx and atx side by side, the mtx definitely is quicker and more nimble. And, it seems to be getting significantly better mileage - over 25 compared to around 22 for the type of driving I've been doing.
Here is a photo of the car w/ the stock atx front springs after the installation of the mtx assembly:
Here is a photo of the rod bearings I took out of my "new" engine when I changed them. These are from a reportedly 130k mile engine, but may not have been the originals:
Here are a couple of random photos of the dead 3.2 coming out of the car:
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