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DIY: Auto To Manual Swap

349K views 420 replies 128 participants last post by  gc_soobs9 
#1 · (Edited by Moderator)
IMPORTANT, IF YOU DO NOT HAVE THE ABILITY OR UNDERSTANDING TO REMOVE AN ENGINE AND A TRANSMISSION, YOU WILL NOT BE HELPED BY THIS INFORMATION, THIS INFORMATION REGARDS PROBLEMS THAT WILL BE ENCOUNTERED DURING AN AUTO-TO-MANUAL SWAP

THE FOLLOWING WILL/MAY BE LOST DURING A CONVERSION

CRUISE CONTROL
ABS (believed to be solved by retaining the TCU and using a resistor to give the TCU the illusion of being in neutral, this doesn't solve cruise control) read more here Legacy Central -- Transmission Conversion and here '98 RS 4EAT to 2000 RS 5MT w/ LSD - NASIOC

CREDIT! I received a large amount of technical and mechanical help From SleepySubieSleepySubie on my project, All credit goes to him, I provided the garage and the budget for this learning experience. CREDIT!


This covers an RS Transmission swap, more specifically a 98 RS Auto to a 2000 RS Manual,

Step 1: Parts collection (the following is specific to my situation, specifics may vary without notice)

Manual Transmission (including mounts)
Matching Shifter Linkage (includes bushings/nuts bolts ect.)
Matching Shifter (Ensure that you have ALL bushings and screws)
Matching Flywheel and Clutch/Pressure Plate
Matching Clutch (master and slave) and Pedals NEED CONFIRMATION, on brake pedal engage switch
Matching Manual Starter
Manual Driveshaft
Manual Rear differential (be sure to match gear ratios, consider this a great time to upgrade to LSD)
Manual ECU Not Required but fuel maps are different between the two. (Same year/trim as your vehicle RS gets RS, L gets L, WRX gets WRX)
your model/trim shifter trim and shift knob (Auto shifter trim offers enough clearance for proper shifting with a short shifter without modification)

We used the 98 RS Automatic CV Axels for both front and rear, if you check with any retailer of rebuilt or OEM replacement parts they tend to use the same part number for both auto and manual variants, which could show either that these parts are the same or that these retailers don't care, I'm going with the first as the 2000 rs axels appeared identical to the 98's (in the rear, the fronts had the ABS ring on the axel vs on the hub no spline additions or extras aside from that) they will, however, charge extra for one or the other left or right on the LSD rear axels, but we couldn't order either to be sure since none of the retailers had any in stock or capable of being ordered.

!!!! If you collect a transmission from a year/model that is not of your own, such as in my case where I purchased a 2000 RS transmission for my 98, you MAY need to keep your speed sensor as the connector varies.

Step 2. Mechanical breakdown (Simple as dirt because this is covered in other DIY's in the forum)

remove the engine, trans, drive shaft, and rear differential.

you will have to remove the shifter trim and separate the automatic shifter from its arbitrary linkage, there will be a few bolts most likely stuck to some degree which you will need to separate from the transmission, if you wish to sell it, you're gonna want to leave that sucker intact. now, what you do with the shifter itself is up to you! As long as you leave the little clips with wires leading away from the shifter alone you will be fine.

Continue to split the Transmission from the engine if you didn't during your original removal process.

At this point, you can check the speed sensor on your transmission, if the replacement transmission has the same sensor you can keep it, if not, simply remove the old one from your automatic and put it in the manual trans.

If your automatic transmission is 98 or older, and your replacement transmission is 99 or newer you will notice that the transmission has 6 bolt locations while your motor has 4.

This will cause no imminent threat to your project! it will cost you another 10-15 dollars. We had to tap a new hole into the starter and purchase a larger bolt to bolt the second end of the starter down, this also requires you to expand the hole on the 2000 MT5 Starter. This secures your starter properly and taping the whole larger doesn't hinder your future USDM WRX swap.

Obviously, you will need to remove the torque converter and flex plate from your engine. and proceed to replace it with your matching clutch, pressure plate, and flywheel. You can now reattach your engine and transmission and put them back into the car. (If you haven't done this before, I suggest installing the starter after the engine/trans are securely in place, less to get caught on)

You will want to install the shifter linkage before you insert the drive shaft as it's going to get in your way, kartboy bushings are great to do now rather than later. and since you're playing with it, go ahead and install the shifter. (leave the trim off till you're done)

Proceed to install the new rear differential and drive shaft, and reinsert the old axles (for the front, you may want to purchase new pins for the inner connection between the axles and transmission)

Step 3: Some assembly required

Now you're going to need to take apart the lower portion of your dash on the driver's side, and gain access to your ECU this will be under the passenger's feet, covered by a metal kick plate.

Start by replacing the ECU (the same years/trims will clip right in)

Next, we will go over to the Pedal box

the pedals you should have purchased need to match your clutch cylinder, from my findings on the 98 (I haven't had the privilege to search other auto or mt5 vehicles other than my own and the donor car)

You will notice the TCU dangling there or bolted onto the Auto brake pedal, this has to be removed, but according to what I've read this controls your ABS system, removing it kills automatic ABS, one simple solution is to get a fully manual wiring harness, manual abs unit, and controller. but that isn't so practical (unless you're doing a WRX swap in which case you really don't need to be reading this) regardless there is information about this problem at the top of the page to refer to, as information is found I'll add it to the DIY

If I am assuming correctly, the manual brake pedal and auto brake pedal are the same, or I'm wrong and the 98 was wired for both pre and post-brake pedal boxes either way you should get lucky and the connectors match or you have both in there, the clutch side, on the other hand, you won't be so lucky, you don't have a clutch switch. there are two options here. you will run a 12 gauge wire directly from the ignition to the starter (yes the starter on the transmission) OR you will run a wire from the ignition to the clip on the clutch pedal (standard spade connectors fit snugly) and run a corresponding one out, all depends on how much you trust yourself to start the car in neutral or with the clutch depressed.

Now for some more wire housekeeping, now if you return to your shifter area you will notice your funny little shifter wiring, ** due to me having lost the pictures I'll be blunt and explain till I get the visuals up** here you have 4 wires on one clip and two on the other, the 2 others light up an indicator to help you figure out what mode you are in when it's dark, it's useless. The other 4 have a great purpose, 2 control a locking motor to keep you from exiting park while the car is off and the other two dictate that it IS indeed in park, (this allows two things, ONE it allows you to take your key out, and two, it turns the fuel pump on, which is kinda important!), the simple man's way of doing it would simply be to take the two that activates the switch (easily known as the ones that DON'T go to the locking motor) and splice them together and retain the clip and plug it into the shifter harness and toss the shifter.

Finally, we return to the engine bay, the following you will have to find wiring pinouts on your own, I will post the RS ones when I post the pictures

you will need the reverse lights, there is also the neutral position switch (I haven't looked it up but we believe its for cruise control which you cannot use anymore), both send a signal, so one goes to ground, and one goes to the reverse light pin. The best way to do this is to locate the Auto wires per those pins and splice them into the transmission sensor wires as you wouldn't want someone hitting you because your reverse lights weren't on. and that's it for wiring!

In a way, you could almost say that you're done! But for obvious reasons, you will want to check and double-check that all of your exterior lights are working as they should. Between now and when you turn the car on, please ensure you have emptied out and refilled both your differential and transmission with new fluid, and unless you're crazy and lifted the engine with the radiator you're going to need to refill that as well.

And as per any DIY ESPECIALLY THIS KIND

I AM NOT RESPONSIBLE FOR ANYTHING YOU BREAK/SHORT/DESTROY DURING THIS PROCESS, OR ANY FAILURE OF THE VEHICLE DURING NORMAL OPERATION, NOR AM I LIABLE FOR YOUR VEHICLE IF ANY BREAKING SYSTEM FAILS AND/OR CAUSES AN ACCIDENT THAT LEADS TO YOUR INSURANCE COMPANY REFUSING TO PAY DUE TO UNANNOTATED MODIFICATION OF YOUR BREAKING SYSTEM

** I TYPED THIS ALL IN ONE SITTING I'M PROOFREADING IT AS WE SPEAK Images will be uploaded soon for now, here's a video of sleepysubie starting my car with no exhaust *

Impreza 2.5 RS No headers - YouTube
 
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#59 ·
just got the subie a week or so ago and already halfway done with this swap. wired up the pedals today. good to know that clip on the clutch pedal is actually needed.

i better get to wiring that thing up to the ignition.

any tips. like, "dont cross the wires it'll fry your starter."
 
#62 ·
-so i had to use the manual starter. no biggie. but the auto starter does not fit in the manual tranny as stated earlier.

-also i just took out all my ABS stuff and plugged in all my manual brakes stuff. its pretty choppy looking since my brake lines are twisted around each other.

-the reverse lights should be easy enough to figure out. just cut the stock clip and put my own clips in.

-the shifter stuff i may have to see to understand. doesnt sound too crazy though.

-i am still a little cloudy about what this clutch pedal clip does. is it just a loop that gets shorted or what. if i can understand what its doing i can understand how to get around it.
 
#63 ·
-so i had to use the manual starter. no biggie. but the auto starter does not fit in the manual tranny as stated earlier.
never said an automatic one would. sorry for the confusion if you picked that up some where.

-also i just took out all my ABS stuff and plugged in all my manual brakes stuff. its pretty choppy looking since my brake lines are twisted around each other.
If you had a brake line bender/extruded you could have shortened and straightened them to look fine. they're fairly cheap at any auto parts store.

-the reverse lights should be easy enough to figure out. just cut the stock clip and put my own clips in.
Purdy much, wiring changes on every vehicle, and I didn't look up the information on every year so that's a home work project for you.

-the shifter stuff i may have to see to understand. doesnt sound too crazy though.
In the transmission tunnel, right behind the opening for your shifter, you have to install bushings for the shifter to mount into. on an automatic car those holes are usually plugged with plastic to prevent rust. pop them out and install the rear bushing. from there the install should go as if you're just installing a manual transmission in a manual car (mechanically)

-i am still a little cloudy about what this clutch pedal clip does. is it just a loop that gets shorted or what. if i can understand what its doing i can understand how to get around it.
Clutch pedal switch is an interrupter that stops the car from starting without the clutch being fully depressed. You can run a line from the ignition column to the clutch and then a second from the clutch to the starter and have your car function like any normal manual car, but if you run it straight from the ignition to the starter your car will start WITHOUT having to press the clutch in.
 
#65 ·
its not called neutral safety for manual its neutral position. And what I'm told it does is tell the ECU you're in neutral this will keep the engine revs up longer wile off the throttle so you can make a clean shift.

This one technically is optional.
 
#67 ·
Clutch pedal switch is an interrupter that stops the car from starting without the clutch being fully depressed. You can run a line from the ignition column to the clutch and then a second from the clutch to the starter and have your car function like any normal manual car said:
so is the line that you are running a ground that is open and when your depress the clutch it connects the negative side of the starter so you can start the car. or is it a 12v line.


also put the tranny in today and the xmember for the 1.8 tranny is waaay off compared to the xmember of the auto 2.2 tranny.

im going to fab one up unless there is an easier fix.
 
#75 · (Edited)
as for the connector on the clutch, its one terminal comes from the ignition switch, other goes to the starter but its optional.

Ok Letze I have a question...I have a 96 L sedan, and im getting the ej20g wrx engine and tranny, will the ecu work w/o problems. Will i have to 1st swap in a 96 L tranny and then swap in the jdm wrx tranny?
It depends on how its wired if it will work or not, thats up to you or who ever you pay to merge your harness.

if you're using a manual ECU, you cannot use an Auto Trans.
 
#72 ·
here is the clutch pedal connector im talking about. (im thinking what if you just jumper the two terminals together what happens. ill check both sides with a volt meter)



these are off of the auto tranny. im assuming we leave them alone. will these cause a CEL.


where do these go.



and finally where do these go.


thanks for the help.
 
#73 ·
one of the 2 big plugs we took the other side from the actual transmission and just made a little harness for it.. i may have a picture of it. The 3rd picture looks like o2 sensor (white plug). I didnt do anything with the connector on the clutch.
 
#78 ·
I just wanted to take a moment to thank Letze for helping all of us in this conversion to rid the heavy, horsepower robbing 4EAT out of cars. On another note, the used 99 5 speed I installed is making horrable bearing noise and when I drained the oil it was mostly gray and had bits of bearing cage stuck to the drain plug. needless to say I am going to have to pull it out once again. i just bought a 98 outback 5 speed that had no bearing parts stuck to the drain plug so I think im going to slap it in and hope for the best. I will take pics of how I modded the starter mounting and give you a first hand pin to pin pics of the wiring before I make it look pretty and legit.
 
#82 ·
not exactly the 5th gear in the RS transmission is a ratio of .780:1 ratio. that is 22% over driven. The outback transmission 5th gear is .871:1 ratio which makes is only 13% over driven. so I will be at high RPM at the same speed in the out back transmission but it will get rid of that hitting a wall feeling that you get when you try to accelerate in 5th gear or so I hope.
 
#83 ·
so ive got the shifter thing shorted together.
and i have also jumpered two pins on the 12 pin connector that used to connect to the automatic tranny. (they are two thicker wires)

car still wont start. i have a few harness clips that arent connected to anything under the dash.

im stuck at this point.

oh yeah the o2 sensors are not connected. (but could this cause the engine to not start at all)
 
#84 ·
i found a good diagram that shows where and what everything is doing. by taking that 12 pin plug that goes to the AT and jumpering pins 11 and 12 (or the thicker wires coming out of the backside of it) you are shorting out the circuit to the starter before the clutch ever comes into play. thus you wont have to push the clutch in to start the car as was stated numerous times before.

so my next step since this is already done is to check that this jumper from pin 11-12 is actually seeing gnd. if its not then i have to trace from there.
otherwise i am thinking of just installing a pushbutton start.
 
#85 ·
ok i checked my little jumper wire. turns out it wasnt sending a gnd because that wire had an open that was under the heat shrink.

so i just some solid core wire in there (tested continuity with a multimeter) and got a click from the starter.

turns out my problem the whole time was that stupid jumper wire. after further troubleshooting my battery needed charging and a wire brush too.

it cranked right up after getting a jump.
 
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