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Old 12-25-2014, 10:35 PM   #1
Scooby Specialist
Member#: 16318
Join Date: Mar 2002
Chapter/Region: NWIC
Location: Kirkland, WA
2002 WRX Franknwagen
Grime over Sedona Red

Default '02 WRX wagon auto to manual drive train swap...a cautionary tale

The elephant in the living room: WHY??
- Original '02 manual car was t-boned in the passenger door, e.g. totaled...but no drive train bits were damaged. I loved that car...sob
- I wanted to re-use my Prodrive PPP3, my 4-pot brakes, rear disks/pads...
- I bought the car back from the insurance company, and found a clean, one owner, '02, same color, decent price...but auto
- Couldn't wait around for another car, so I bought it
- I have the full factory shop manual set: an absolute prerequisite!

Eventually I got around to the swap. Everyone I knew in the community thought I was nuts, but gottas have that manual back.

I've been mucking about with mechanical stuff my entire life, and quite a bit with Subarus, so the mechanical stuff was straightforward, but rather laborious doing it all myself with limited garage space to work in. The fact that I was working with 2 cars of the same body / engine / year eliminated all the mechanical pitfalls discussed in countless other conversion threads. Piece of cake.

NOTE: I'm glossing over all the minor details here, like getting the front axles out of the trans, attaching the engine to the hoist, etc., etc., etc...

Also note, as mentioned in many other threads, the rear diff ratio is NOT the same between manual and auto: you MUST swap the diffs also.

There was no (practical / safe) way to get the car up in the air far enough to get the trans(s) out / in from under the car...so I pulled both engines w/ trans attached. Worked fine, just took it slow and carefully. Moveable engine hoist absolutely essential...

A handy trick to installing the engine w/ trans attached: fold up some sturdy corrugated cardboard to tuck between the trans and the firewall end of the trans tunnel. Worked like a charm, 'cause the unit has to go in at quite a steep angle to avoid body structure bits. Cardboard was slick enough it just bent to fit the body and the trans slid right down and back into place. Ymmv...

There are 2 ways to swap the rear diff: yank out just the diffs and swap them, or swap the entire rear subframe. Swapping just the diffs seems like the obvious answer...but you actually have to do more disassembly / reassembly that way. The entire rear subframe comes out with 4 bolts. No disconnecting suspension bits to get the axles out, no de-mounting the diff while getting fluid everywhere, etc. Plus I knew my rear brakes were in good shape and was going to keep them in either case.

Of course, the entire subframes aare a bit heavier than just the diffs, and need to be supported. I used a floor jack, both to support them under the car and move them around.

I elected to pull the emergency brake cables with the subframe. Disconnecting / reconnecting in the car is a giant pita, though, so I'd look at how difficult it would be to disconnect at the brakes.

Ok, the mechanical stuff's all done (!?). So, how 'bout that electrical?

The good news: the instrument pod is just a straight swap! And in many cases - but not all - you can tap into the circuits you need using the existing auto harness connectors. Once you've figured out the "details".
The bad news: that's all the good news there is.

I'm pretty good at electrical stuff, and I did get it figured out. Eventually. The factory electrical manual is absolutely essential - once you've figured out all the place where it does NOT show you the info you desperately need:
- There are some excellent pages that show the different wiring paths and components for manual vs. auto installs.
- There are many other pages that show only one or the other...and don't tell you which.
- Many of those other pages lead to wrong assumptions, subtle conflicts in the info, considerable creative use of language, and hair loss.
- The ECUs are identical - except they're wired differently in a couple of critical places.

After exhaustive analysis of the manual I did find ways to connect to the existing wiring harness for all but a couple of connections in the cockpit. So I only had to run 1 (2?) wires through the firewall.

Everything works, and Frankensubie is again a joy to drive!

The astute reader has probably noticed the lack of actual wiring details above. That's because I'm writing this on a whim, and I'm not where I have access to all my notes/diagrams/scribblings/ and the manual.

If anyone actually needs those details at this late date I can come up with the answers...

- Can you perform this swap between, say, an '02 and '03, or an '05 and a '12, or...?
- I don't have a ******* clue, and I wouldn't presume to guess.
- One would think that '02 - '05 swaps would be pretty straightforward, but...I won't even guess.
- Do not, under any circumstances, consider this swap in the opposite direction. Mechanically, no problem. Electrically...only the clinically diagnosed masochist should attempt it.

Hopefully this will be enlightening to the innocent, remotely helpful to anyone insane enough to attempt this, and roll on the floor to those who have been there...
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GravelRash is offline   Reply With Quote
Old 12-26-2014, 05:16 PM   #2
Scooby Newbie
Member#: 316863
Join Date: Apr 2012
Chapter/Region: E. Canada
Location: Southern Ontario
2003 WRX Wagon
Midnight Blue


I was under the impression that swapping the main harness that runs underneath the dash would make this swap so no wires had to be tapped into... Maybe you didn't want to pull the dash? Or maybe my impressions are wrong
hopperjon is offline   Reply With Quote
Old 12-26-2014, 08:53 PM   #3
Scooby Specialist
Member#: 16318
Join Date: Mar 2002
Chapter/Region: NWIC
Location: Kirkland, WA
2002 WRX Franknwagen
Grime over Sedona Red


You're probably not wrong, for the most part. You're definitely not wrong that I didn't want to pull the dash.

I didn't have to actually tap into the existing cockpit harness wires. I just used some generic spade connectors that I trimmed one leg off of, and the remaining leg plugged into the appropriate existing connector socket. Most of these plugged into the 5 connectors that used to plug into the auto trans controller module, conveniently located above the clutch pedal. Far, far, easier than pulling the dash and swapping the harnesses!

Note: for every item that was connected to a harness in the manual car I generally left the plug attached, and cut the wires as far back from the plug as was convenient/possible. So I had wiring to attach new connectors to, and/or extend to reach the necessary connection on the auto cockpit harness. (I also salvaged every other connector in sight, with as much wiring as was convenient, just for future reference. I have a milk carton crate full of that stuff...)

Example: the wires coming from the clutch pedal position switch(es?) can be either siamesed with the brake pedal switch(es?) connectors, or have a trimmed spade connector added and plug into one of the aforementioned trans controller sockets.

Even if you do pull the entire dash, the main cockpit harness wraps over-under-around-and-through so many openings and structural bits that it would help to be a snake charmer. And the harness is securely taped to something just about everywhere you can't reach. Plus it has a bazillion other connections that have nothing to do with the swap. And you'd have to unplug every one of them, and then get them all plugged back into the new harness. Add different connector colors and configurations, and mounting locations/orientations, and I don't know if it would all actually be plug-n-play...

And that still leaves you with the one connection from the engine compartment to the ecu: the manual trans speed sensor. There's no workable connection from the sensor to the existing engine compartment harness, and no access to that circuit in the cockpit. And really, pulling one wire into the cockpit isn't a big deal, just a pita to route it neatly all the way over to the ecu.

I'd love to swap stories with someone who actually did the cockpit harness swap. Assuming, that is, that they're not locked away somewhere under heavy sedation...

Originally Posted by hopperjon View Post
I was under the impression that swapping the main harness that runs underneath the dash would make this swap so no wires had to be tapped into... Maybe you didn't want to pull the dash? Or maybe my impressions are wrong
GravelRash is offline   Reply With Quote
Old 12-26-2014, 09:11 PM   #4
Scooby Specialist
Member#: 16318
Join Date: Mar 2002
Chapter/Region: NWIC
Location: Kirkland, WA
2002 WRX Franknwagen
Grime over Sedona Red


One other little quirk that you won't find in the manual. If you leave the key in the ignition of the auto car when you pull the battery...you can't get the key out of the ignition switch. Ever.

Or, if you did remove the key, once you've done the swap and you insert the key and fire it up, and everything works just like it should, when you shut off the ignition...you can't get the key out. Ever.

Unless, that is, you find the appropriate connector that came off the auto shift lever module and permanently jumper the 2 connections in the plug. That bit was connected to the switch for the Park position of the auto shift lever...which controlled the locking mechanism in the steering column that prevented you from removing the key unless it was in park. No "Park" position, no remove key...

Or, of course, you could just swap the entire steering column over from the manual car. Whichever is easier...
GravelRash is offline   Reply With Quote
Old 02-09-2015, 02:58 PM   #5
Scooby Newbie
Member#: 413060
Join Date: Feb 2015

Nice thread man how long did it take you to get it all done ?
& did the tranny mount up to the engine exactly ?
Planing to do the same but from a 02 to an 04
Rex34v is offline   Reply With Quote
Old 02-10-2015, 11:45 AM   #6
Scooby Newbie
Member#: 399786
Join Date: Aug 2014
Chapter/Region: MWSOC
Location: Michigan
2002 02 wrx Saab 92x


A lot of very interesting info here. Way more consolidated and to the point than other swap threads.

I too was tboned in my 02 wrx wagon and a friend of mine gave me his auto 02 wagon. He was planning on doing an STI swap and jumped on a rolling chassis that he got for a steal. Only problem is it's an auto and he didn't realize the pain in the ass it would be to convert 👎.

His loss, my gain.

So what I've gathered for my best plan of actuon is the following:

1. Swap out entire rear subframe.

2. Pull dash and replace entire dash harness and trans harness.

3. Replace entire steering column with components.

4. Drop trans, manaul ecu, engine and harness in.

5. Done.

Obviously easier said than done, but is this the gist of it? The most direct route without having to cut and splice wires? I'm not good at that and I'd like to avoid that head ache.
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