How-To : ATX to MTX Swap Info.

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How-To : ATX to MTX Swap Info.

Post by Lackof » Tue Feb 06, 2007 12:17 am

Last edited by Lackof on Mon Jan 21, 2008 2:13 am, edited 1 time in total.

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Post by krat0s » Mon Feb 12, 2007 9:38 am

Don't forget to replace the rear main seal when doing this!

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Post by glasswars » Mon Feb 12, 2007 9:43 am

Good info. Thanks!
01' Neon.
Member #20.

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Post by fusion210 » Mon Feb 12, 2007 3:46 pm

Since we are neon owners and cheap, you can reuse your atx pcm.
If you leave it as is, you will get a code for the tq converter lockup solenoid, well, since you don't have one anymore!
In order to get rid of the code, take the tq converter lockup solenoid out of the transmission, plug it in, and zip tie it aside like so. ... 010243.jpg
It is the sensor that is blue, next to the pcm. Note my crappy wiring, make yours better than mine.
However, the atx pcm with sometimes fight with you for idle while slowing to a stop both in neutral and in gear, causing some bucking when in gear or it will hold 1500ish rpm while coasting in neutral, the pcm will always win that one. I highly suggest getting a mopar or af/x reprogrammed pcm if you are going to stay naturally aspirated, or a cheap mtx pcm.

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Post by Lackof » Mon Feb 12, 2007 4:15 pm

right on great info. added gise.

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Post by spoo76 » Mon Feb 12, 2007 6:39 pm

this is a VERY old post of mine from and i just decided to copy it over seeing as how more and more people are swapping
ive also updated some of the links and Info

Spoo76 wrote:
Tranny swap tipsok some of this is just info i collected from other sources
3.55 or 3.94 all dohc neons came with a 3.94 but the R/T and ACR neons have a different final drive and 5th gear i think the first sohc ACR's had the same 5th and final as well

the 3.94 seems to be the best choice for the all motor or lower power cars because of the gearing

the 3.55 seems to be the best for the high power or turbo guys

check here if you know your tranny vin to see which you have and other tranny info
on the bottom left you can change the menu from
PLT350 ( Neons )
PLT850 (Neon SRT4 )
and PT ( PT cruiser )

vin plate looks like this

prices vary on lots of things. if you have the option get a donor car and sell everything left over. other wise look on the forsale boards or local or internet salvage yards
for me the prices were
$250 for the shifter,brackets,passenger axle, and all the other misc items
$200? (I don't remember) for my 3.94 tranny
$30 average for a new throw out bearing
$30 roughly for mopar MTX tranny fluid (really recommend only mopar fluid)
$280 (i think) for the LUK modular clutch (clutches vary in price quite a bit)

optional upgrades:
$100-175 used afx or Mopar performance since you have to replace the ATX ecu
$200 mopar short throw shifter or maddog
$25 jeff ball's booger bushings (definitely cool)click here for his site
$25-30 booger strut (highly recommended)click for mount
You can also use vitors bobble strut,
and bobble strut mount if you have a welder but No MTX K-member
click here for his site

parts you'll need
(1) Vehicle speed sensor appropriate for your year (rear of tranny)

(1) Left transaxle mount, AKA engine mount (in strut tower area on drivers side)

(1) Shifter cable bracket

(1) Bobble strut, upper mounting bracket, and bushing

(1) Clutch (recommend a new clutch) a modular clutch is easier

1 new throw out bearing

(1) Drive axle tranny side

(1) entire clutch/brake pedal assembly. including any switches or sensors

1 clutch pedal stop (grey plastic thing) at the end of the cable attached to the pedal

(1) Shifter assembly (with knob and boot)

(1) Shifter linkage cables

(1) Clutch pedal position switch

(1) Clutch cable

(2) Shift cable retaining clips

(2) Shift cable retaining clips (for the other end)

(1) The longer of the two engine to transmission brackets

(1) K member from a MTX neon. recommended over welding a bracket on the auto kmeber(its easier if you dont have someone to weld)

(1) Plug for the reverse light switch on the tranny with the pigtail of wiring (front of tranny)

(1) Bobble strut (recommend aftermarket solid bobble strut)

1 computer from a manual car for your year car..aka ecm, pcm, ecu
car will work with the auto but the rev limit will be pretty low @ 55k or so and you will have the check engine light

2.5 quarts of tranny fluid (that's 2 and a half bottles only use mopar fluid)

new cotter pins

high pressure high temp grease

some extra wire for the reverse light plug. and the clutch pedal switch



tools you may need
1) Sockets (in mm): 8, 10, 13, 15, 17, 18, 19, 21, 32 (hub nut socket)
2) Breaker bars
3) Pry bars (I suggest one long one, one midsize one)
4) Hydraulic Jacks ( I suggest 2)
5) 2 jack stands
6) Screwdriver assortment
7) Ratchets: 1/4, 1/2, 3/4 drive
8 ) Torque wrench
also a hayes or factory service manual will help a lot
lots and lots of extensions for the socket wrench..short ones and long ones

wire cutter/strippers

locktite or similar product

also wouldn't hurt to have some liquid wrench or WD-40
i definitely recommend a breaker bar if you don't have air tools
my big as red 3 foot crowbar (named tina don't ask) is what i used to get the clutch cable on

lots of plastic baggies and a sharpie for the misc bolts..(makes life a lot easier when they are separately labeled)

some tips and stuff some of which are from others that helped me out

be prepared to make trips back and forth to the parts'll likely break or lose something or you my want to replace old parts..

while you have everything apart now would be a good time to check if you want to replace brakes,rotors,suspension bushings..
the rear main seal while the trans is out, you will be sorry if you don't

also if you have the funds why not replace stock parts with better parts?
i got a LUK modular clutch,mopar shifter,booger bushings and booger strut, and an afx ecu. also you can put on a fresh set of rotors and better brake pads if needed..or since you have the suspension apart put in new rubber bushings or prothane/energy suspension bushings..also you could put filled motor mounts now too

the pedal assembly seems to be a pain but once you figure out how to get around the steering column its not to bad.after you unbolt it, it will be glued to the plastic/rubber..just pry it loose,,you might want to pull the brake booster a little out from the engine makes things a lot easier..also remove the drivers seat to give you some room

the flexplate is keyed to the flywheel so make sure you have it on correctly (the bolts are keyed in a certain order)

put the clutch/flywheel into the tranny before you put the tranny into place (don't forget to have the throw out bearing on there(lubed of course)

when putting the clutch cable on you will want to use a crowbar to push the clutch lever (inside the tranny) so that the cable will be long enough to go onto the clutch pedal(this part sucked)

take off the flexplate and make marks on the flexplate to the flywheel to how it should go into place... use a sharpie... make a mark on the flywheel and flexplate
put the tranny into place and get under the car, have someone turn the crank (by the crank pulley) until your marks line up and bolt them into place by turning the crank to turn the flexplate/flywheel

NOTE: i didn't do it this way and i had to keep moving the crank till i had the right lineup

clutch pedal wires (directly copied) this is not needed but the car will start in gear if you don't wire this. in my opinion do the wires last

The clutch safety switch has a solid yellow wire and a yellow wire with a red stripe on it. Locate the larger gauge solid yellow wire under your dash in the wire loom. Cut that wire... The solid yellow wire that comes outta the safety switch will be connected to the solid yellow wire (larger gauge) that you had just cut (the end that seems like is coming from the fuse box). The yellow wire with the red stripe will be connected to the other end of that solid yellow wire (larger gauge) which leads through the fire wall.

All the wiring consists of.... clutch safety switch, reverse lights switch (which are patched into the outside wires on the neutral safety switch), and the center wire on the neutral safety switch needs to be grounded.

When you locate that thick gauge solid yellow wire, you will have to cut it in the center (where both ends are about the same length) there is not a lot of wire there to play with. You have about a 4 inch length there to work with, 2 inches after you cut it. The side that I referred to as the fuse box, is the side that is NOT actually going through the firewall (speaking after you cut the wire)." - author unknown

or the more simple way....there should be a yellow wire in the main harness that goes from somewhere in the steering column, out that giant ------ rubber plug thing that all the wires go though.... you have to cut it. and wire one side to each terminal on the clutch pedal connector

reverse light plug in engine bay on front side of tranny

the connector with two wires on it is useless. just zip-tie it up somewhere......

the connector with 3 wires. needs to be cut off on the plug end

you need just the wires... cuz you need to splice those wires into the MTX reverse light plug

the two purple wires go together... then the white wire goes to i believe the yellow wire on the car harness,. and the brown wire gets grounded to the frame

(in my case it was purple-purple, white-white and yellow/with brown stripe gets grounded)


In my opinion the swap was well worth it and wasn't that hard at all just make sure you have at least 2 people. and if you don't have air tools definitely get breaker bars there will be some tight ------ bolts.
the car is faster more fun and pulls so much harder. if you do it you'll love it.

and also this Info was from fusion210
this will get rid of the CEL if you use the ATX computer, but you will still have the lower rev limit of the stock ATX ECU
fusion210 wrote:To use the automatic's computer with the swap you just have to do this.
Before you remove the auto tranny from the car and while you are draining it remove the pan.
Remove the manual valve body.
Take off the torque converter lockup solenoid connected to the vavle body.
Zip tie it to the wires by the side of the computer and plug it in.
Put back in the valve body and pan.

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