5s swap into my H6 opinion

[Shane01BH]

Hi all. Just for flaming, I have read the posts about Trans Swaps and so far I'm not turned off.

For back story here is my car https://sl-i.net/FORUM/viewtopic.php?f=6&t=24669

For my reasoning here is my inspiration https://sl-i.net/FORUM/viewtopic.php?f=31&t=12871

So on to my search for opinions.

Reading through too many posts, the main red flags I see for a swap of this type is the large amounts of specialized parts in the BH/BE chassis that are not present in the Previous and Post Legacy models. So parts swapping becomes an issue.

Right now I have come across a crunched (as in salvaged) 2004 Legacy GT with a 5s. The body is toast, but the drivetrain is suppose to be in fairly good shape. About 12k less miles than my car and it runs. Would this by a wise investment for my swap as the donor car is currently half the price of buying a used STi 6s.

Reading through keltik's post, it seems that most of his issues were trying to find BH specific parts.

Feel free to challenge me. So far my wife isn't against the theory of having a parts car in the driveway while I work on it. I'm just worried it may take me a months to get it sorted.

[Huffer]

You can install a 5MT into the BH and bolt it to the H6. Physically it'll fit. You'll need the appropriate clutch mechanism, pedal box, and be prepared to do a small amount of wiring to get the ECU to think it still has an auto transmission. From what I understand of the earlier H6 (the EG33) the work around was to leave the 4EAT's TCU installed and plugged into the harness. Because the 5MT is completely mechanical, it doesn't need to tell the ECU "hey, I'm switching from 1st to 2nd". The only issue might be with the Neutral switch.

BTW - you won't have 1 parts car while you do this - you'll have TWO.

[Shane01BH]

Ha yes I would have two parts cars, don't tell the wife.

The clutch mechanism and pedal box is why I'm looking at a full parts car instead of buying a piece at a time.

I'm hoping that minimum responses are a sign of "go for it"

[Yamazaki]

I say go for it and document the progress in great detail. There are some others of us with H6s that might like to do that someday but are too scared to go first.

[Huffer]

^^ Yama, it's really the same process that the SVX guys go through installing a WRX 5MT into their cars.

[Yamazaki]

Really? That's cool then. I thought there was something about the newer ECU that made it more difficult.

[Huffer]

It's the same story of the ECU looking for the Auto ECU to make sure it's shifting appropriately based on RPM. As long as the ECU has somewhere to send it's signals, and the TCU can send them back, everything should be fine. Now, if you started looking at using the 5EAT that might be a different kettle of fish because the TCU has one additional gear, but the factory ECU is still only programmed for 4...although its possible that the ECU just hands off that decision making to the TCU...which actually makes more sense really.

[Caboobaroo]

I've also been looking into doing this swap (never been a fan of Subaru slush boxes) and the ECU recieves a pulse signal from the TCU for the torque converter. I know the older automatic ECUs just look for an on/off signal from the TCU instead, which makes it easier. Pretty much just ground a couple pins coming from the ECU to fake it and it runs fine. Haven't played around much with OBD2 automatic harnesses, mostly OBD 1/per OBD.

On the 80s stuff with a 3AT, it's a matter of jumping the neutral safety switch. Oh I wish it was that easy.

[1055]

I know this thread is older.. but I just so happen to have a complete 5 speed drivetrain and pedal box..