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Old 12-25-2014, 09:35 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...
GravelRash is offline   Reply With Quote

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