Engine Swap - Will this work?

Hey All,

Im planning on giving my current N/A SF Forester a new heart out of the turbo GT version but I want keep the dual box from the N/A gearbox. I am aware that this gearbox is very weak so I'd be looking to take a box from an SG forester with dual range.

So my question is:

Will an SF GT engine and SG gearbox work?
Is anyone else running this?
What troubles am I likely to run into?

Thanks in advance!

Last year I put an 07 WRX engine in my SG N/A 5 speed with dual range. My advice would be to buy an XT and stick a dual range in it with the correct ratio rear diff. My build is here, although the engine swap is towards the end. What you plan will work. You will need to replace so much, from cross member, exhaust, fuel pump, wiring, ECU, although a lot of this can come from the donor car. Also cruise control, bonnet, etc, etc, etc.


https://www.offroadsubarus.com/showthread.php?t=2091

yep - it'll all bolt up.

I expect the forester swap would be similar in complexity to my twin-turbo-engine-in-an-outback conversion (see my build thread at subyclub)

Rally is right - most of the work is not related to gearbox or engine.

A gearbox swap into a GT is much more straightforward - bolt in.

Putting in an engine from a front-cut/wrecked GT donor and you're looking at swapping over all the engine electrics (ECU + wiring from the bulkhead forward), engine subframe (turbo subframe has a dent for the dump pipe), exhaust, fuel pump + controller (minor rewiring back to tank). If you pick the right donor/recipient combo (ie: same forester revision) - then with any luck it'll just be plug and play for the bulkhead and engine wiring harnesses.

If you do a different route (say WRX engine), then you'll probably have to splice harnesses - which then becomes another can of worms best left unopened.

You may want to go the more complicated route to save some $$ - as JDM GT forester cuts are probably cheaper, more plentiful, and of better general condition than what you can find locally.

And if you do go ahead and plan to do the re-wiring yourself, you need to know that the factory worksop manuals are invariably wrong. Which means you need to have above average auto electrical ability. Or pay someone a lot of money to do it for you. I'd go with a 2.5 litre engine because they have so much torque. But then you'd want to do what I did to mine- LOTS OF WORK. Which brings you back to getting an XT and sticking the dual range in it, etc.

Rally said:

Last year I put an 07 WRX engine in my SG N/A 5 speed with dual range. My advice would be to buy an XT and stick a dual range in it with the correct ratio rear diff. My build is here, although the engine swap is towards the end. What you plan will work. You will need to replace so much, from cross member, exhaust, fuel pump, wiring, ECU, although a lot of this can come from the donor car. Also cruise control, bonnet, etc, etc, etc.


https://www.offroadsubarus.com/showthread.php?t=2091

Click to expand...

Getting a full donor car is the plan, preferably getting one with a few bashed in panels or something so its a bit cheaper. Surely if I do that its just a process of swapping all the running gear and the SG box into my forester? Getting to see it come off an already running GT would make the build easier imo
The reason I've chosen not to just buy a GT and swap the box in is that my n/a is quite lifted and I was thinking that the engine swap would be less hassle and cheaper than swapping all the lift over onto a tidy GT.

I think Rally's right.

Far easier to swap suspension bits between cars than it is to splice wiring looms, etc, etc, etc ...

Agree with the above advise Aids, sell your car and buy a turbo one. It will save you a huge amount of work.

aidan - I don't want to dissuade you from either path.

Just make sure you go in with a plan and your eyes open regarding the things you'll need to address.

Wiring the loom, as mentioned above, is a hassle if the donor doesn't match, but if you don't have the skills or motivation to do it yourself, can be resolved with about $1k to someone like AMAuto who will make a plug and play conversion loom for you.

I don't know how much luck you'll have finding a reasonable condition GT donor -- so make sure you check around a few reputable Japanese importers for front-cut options.

The auto electrical work alone on my car alone would have cost $2,000-$3,000 if I paid someone to do it. Conversions are never easy, not unless you do the same one for a living day in day out. Things is, if you get an XT, you get the 2.5 litre engine, which is so torquey. Sure, you need to do a couple of things to it for reliability, but nothing more than replacing the oil pick up, windage tray and sump. I've done gearbox conversions and engine conversions on Subarus. Gearbox conversions are SO much easier.

Thanks for all the responses, glad I made the post. I think I'll try bringing my n/a back to stock, selling it, then buying a good GT and just drop the new gearbox into that. Sounds like it will save a lot of stress and money.

BTW Aidan, a warm to the ORS forum, mate :biggrin:.

Thanks Ratbag! Subie communities are always good ones, especially offroad ones I'll make sure I post up some pictures of what I end up doing

aidanmair said:

Getting a full donor car is the plan, preferably getting one with a few bashed in panels or something so its a bit cheaper. Surely if I do that its just a process of swapping all the running gear and the SG box into my forester? Getting to see it come off an already running GT would make the build easier imo
The reason I've chosen not to just buy a GT and swap the box in is that my n/a is quite lifted and I was thinking that the engine swap would be less hassle and cheaper than swapping all the lift over onto a tidy GT.

Click to expand...

Perhapse a front cut import would do the trick.
I'm relatively new to this concept but from my research, it may solve your probs.