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Old 07-20-2014, 10:22 AM   #1
waiguoren
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Default Modified 5MT to modified 4EAT

Has anyone modified a WRX by replacing a 5MT with a 4EAT? There are plenty of threads that deal with replacing a 4EAT with either a 5MT or an STI 6spd, but I can't find any that deal with going the other way.

Yes, I realize there is a reason for this. The thought of replacing my modified 5MT (Albins gears, etc.) and Spec 2+ with a 4EAT is depressing, but injuries and wounds and a really nasty reaction to meds given to me by the VA (not the doc's fault; it was a good call, and it was backed up by a team of civilian docs) have left my left foot feeling as if it has been gnawed on by a shark with dull teeth. I've been on crutches for going on two months. My car is literally gathering dust. I can't use a clutch.

I'm an old guy, and I intended this car to be my last car (2002 WRX Wagon). I've used it many times to travel from Montana to both coasts and to the Midwest. I've never had a better touring/sports car. It gets 26.5 mpg at 75-80 mph. I can up this slightly by using different tires and by using a map designed for sea level, but only slightly.

We've managed to de-tune the engine to about 345 whp/325 wtrq. I think a 4EAT with a modified torque converter, etc., will easily handle this kind of power.

But I'm not sure what needs to be done. Do I need a new wiring harness? Different rear diff? If I'm going to do this, I want all my ducks in a row so that I can get it done quickly. I will have the help of a first-rate mech who is well experienced modifying American muscle. He is well experienced with normally aspirated Subies. I have personally extensively modified both WRX and Forester XT's, but have never done a transmission swap. I'm partial to a modified Subaru 5MT with Albins gears.

Yes, I'd happily swap for a Bugeye WRX Wagon with 4EAT or a modified Forester XT with 4EAT. But I can't find one that hasn't been ruined by poorly thought out mods and/or poor maintenance. Generally speaking anyone with an auto is not interested in a beast with a manual transmission. And selling my car outright--well, if I do that there's no way to recoup even a fraction of the cost spent building it. In fact, I'm sure I could easily make more by simply parting it out. If I can't trade for a good Subie with a 4EAT, or can't swap the transmission, then I reckon I'll just let it gather dust.

Any advice will be greatly appreciated.
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Old 07-22-2014, 11:57 AM   #2
waiguoren
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Someone!?
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Old 07-22-2014, 12:54 PM   #3
69subaru360
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To start with you will need the complete bulkhead harness from an automatic plus the obvious stuff. TCU, shifter, crossmember, matching ratio rear diff, driveshaft.

It can be done but it's a big undertaking, you will have to pretty much gut the interior out for the wiring.
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Old 07-22-2014, 01:58 PM   #4
Jubert69
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^^ What he said.

My advice. Don't swap it. Going to be a PITA. Wiring my previous WRX from 4EAT to 5MT was annoying enough. Couldn't imagine going the other way.
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Old 07-22-2014, 08:17 PM   #5
waiguoren
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Why can't I just reverse whatever it took to swap for a 5MT? I assume that the two wiring harnesses are the same. Some wires are used, others aren't depending on the transmission. I might have to add a few wires but that's no big deal. All the mechanical stuff is easily done. I don't think I'll have any trouble selling my 5MT and related parts. It's a hell of a transmission.

I've tried to trade for a 4EAT wrx or forester XT. No luck. I've looked for a good used 02/03 bugeye wagon with 4EAT or a good used 04/05 Forester XT, with the thought of simply swapping everything in the engine compartment, most of the suspension, etc., etc. But no luck.

I can no longer use a clutch. I'd like to keep my car because it's a one-of-a-kind, the best touring/sports car I've ever driven. I'll have plenty of professional help to do the swap, as long as I get all my ducks in a row before we begin.
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Old 07-22-2014, 10:21 PM   #6
Jubert69
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By all means, do what you want to do.

Just my opinion. The reason why I said not to, wiring. Wiring the TCU will not be easy. There's extra plugs here and there and I just see it as a big headache to trace. Once you start, there's really no going back. Right now in my other car that went from 4eat to 5mt, there are 3 giant plugs below the top mount that are not being used.
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Old 07-23-2014, 12:23 AM   #7
waiguoren
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Believe me, I'm hearing what you are saying. And I'm starting to think that replacing the wiring harness is the way to go. Both the engine and the trans will be out of the car. I've got some things I want to do to the engine that will require removing the heads, and it's about time to replace all the timing stuff. The guy who will be helping is well experienced in wiring cars from the ground up. I absolutely do not want to do this, but don't see any way around it. Last year, I took two trips to Bloomington, Indiana during some truly unreasonable weather. It's 1,968 miles one way. I can't think of another car or pickup truck that could have performed as well. It's taken me years to build this car into its present incarnation; it is the product of years of racing both cars and motorcycles. I don't want to throw all that away.

Thanks again for the advice.
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Old 07-23-2014, 01:17 AM   #8
02 RS
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First of all, thank you for your service. Really, thanks, and I'm sorry to hear about your injuries (no matter what the cause).

Secondly, you might be better off finding a harness from an auto WRX/WRX Wagon, or finding a wrecked one and part out what you don't need, thus possibly doing the swap for free (or a profit! ) I know the ECU's are the same, and the drive shafts are shorter, but everything else, I have no idea.

I'd start here: http://forums.nasioc.com/forums/show...ht=4eat+thread Found in a minute of searching with my limited knowledge on the subject.

I only read through that thread a few minutes but there seems to be some knowledgeable auto trans folk in there (I think).

There IS information out there, it's just really hard to find. Try PM'ing some guys in this thread and see if they have any info.

As far as I remember all the parts I found for a built 4eat were from overseas (AUS, EU, etc.) If your looking to go that route.

I also know that P&L uses autos in some of their drag cars, but I don't know if they're Subaru autos.. (some of them appear to still be AWD)

Good luck man, I hope you can keep enjoying your car (and sorry for the word vomit)

Thanks Again, and good luck,
Ben

Last edited by 02 RS; 07-23-2014 at 01:32 AM.
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Old 07-23-2014, 09:40 AM   #9
waiguoren
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Thanks. I've pretty much decided to replace the wiring harness. As far as the trans itself is concerned, once I find one, I'll modify it myself (high-rev torque converter, etc.)

The biggest headache is going to be coordinating the acquisition of new parts with the sale of parts related to the 5MT. People are already lining up for the trans and the clutch, but, of course, they want them right now. That's not going to happen.
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Old 07-23-2014, 12:42 PM   #10
69subaru360
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Quote:
Originally Posted by waiguoren View Post
Why can't I just reverse whatever it took to swap for a 5MT? I assume that the two wiring harnesses are the same. Some wires are used, others aren't depending on the transmission. I might have to add a few wires but that's no big deal. All the mechanical stuff is easily done. I don't think I'll have any trouble selling my 5MT and related parts. It's a hell of a transmission.

I've tried to trade for a 4EAT wrx or forester XT. No luck. I've looked for a good used 02/03 bugeye wagon with 4EAT or a good used 04/05 Forester XT, with the thought of simply swapping everything in the engine compartment, most of the suspension, etc., etc. But no luck.

I can no longer use a clutch. I'd like to keep my car because it's a one-of-a-kind, the best touring/sports car I've ever driven. I'll have plenty of professional help to do the swap, as long as I get all my ducks in a row before we begin.

It's not a few wires. It's a 2" thick bundle of wires not there. You need an automatic harness, a TCU and a few other little boxes IIRC.
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Old 07-23-2014, 06:17 PM   #11
waiguoren
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I've resigned myself to replacing the harness, adding a TCU, but what "other little boxes" are you talking about?

A friend in Japan who has an STI is contacting friends of his who are Subaru engineers. They all have modified Subarus of one sort or another.
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Old 08-19-2014, 07:05 AM   #12
djravechild
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Default would following the 4eat to 5mt backward work, whats th e best thread

I am hoping to figure out the 4eat to 5my, just picked up a 2005 wrx that came with the drive line. Just need to do the work but I'd identifying th best method so far has been challenging. Is there any full success swaps listed, I ask cause there is a lot of threads.
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