Busy workweek this week - but I got some really wonderful weather today and took the opportunity to get the next notable step dealt with - making the threaded mounting points for the impreza diff subframe.  Also before I get too far into it, a  protip/safety tip:  if someone finds themselves recreating this, or if I decide to do it again - make sure you're using plain, non-galvanized tubing. I'm sure someone has spotted that already and was kind enough to keep their yap shut about it 😅  I used what I have on hand and looking back at it the prep work involved to safely weld this stuff with my setup quickly wiped out any minor cash savings I made by not just going to buy another stick of tubing. I'm sure I don't have to go into details about the dangers of working with galvanized material, but it's worth repeating that Zinc is bad for you in gaseous form and if you're gonna encounter it to take the proper safety precautions. 

With that out of the way - the photo essay goods: 

After everything was tacked up and nominally square - I clamped the new frame in its place on top of the bushings, and marked the first hole location for the threaded inserts ( M16 nuts I'm welding in), then center punched and drilled out the hole. I had access to weld the outer half of the nut since it's pretty close to the end of the tube and I used a technique i learned involving some clever placement of smaller access holes to get the inside faces of the nuts fused in. Like the other channels, this will all get boxed in and closed up when i'm happy with the fitment. After this I continued marking and drilling one hole at a time, using the Impreza subframe as a jig to make sure things ended up where they needed to be. I also drilled these holes slightly oversize so that I have a little wiggle room in their placement. Their final positions were dictated with tacks on the welder and then fully welded off of the impreza subframe so as not to melt or damage the bushings. 

 

After the new weldment and sheet metal subframe were temporarily assembled together, I put the diff back in it, put it on the transmission jack and then bolted the diff to the front mounts under the car.  The original holes and features made for a really handy reference mark and wouldn't you know it, things came out super even. So even in fact, I couldn't help but loosely bolt the lateral links in, prop the trailing arm up, and lean the coilovers (not pictured) up in there without any bolts to get an idea of how things are going to sit. 

I can almost see it on the ground again! (It'll still be a while). I don't know if I'll be able to narrow the rear wheelbase quite as much as I'd have originally liked, though with a quick google having a slightly wider rear track isn't uncommon and can actually help with certain handling characteristics. I might have to flare my rear fenders, as I do not think I'm going to be able to reduce the rear width the full 9" (4.5" on each side) or so I originally measured without some pretty significant clearancing wizardry beween subframe and coil. I'll have a better plan of attack here once I've got everything semi-permanently affixed to the frame but either way what this is telling me is that I'll probably need to refrain from fully welding in this frame modification until I've got the suspension completely located. I'm also eyeballing putting in a set of rear discs rather than these drums, as I'm not a huge fan of drum brakes and well... I'm already really in the weeds so why not just do it from the ground up?

Might get a little more in on this over the weekend, but I'll be playing that by ear. 

Until the next one! 

-M

 

Edited December 6, 2025Dec 6 by mka

Sweet! Little at a time.

 

My first thought on the brakes was wondering if anyone has done inboard disks somehow. That would probably take too much money but I am thinking if axles are cut down maybe they could be adapted at the inner ends to accept a disk. Or an existing setup like from a Lotus etc. as an example. 
 

Pardon my freaky thought in the middle of your hard work. 
 

Inboard brakes at the diff, big bash plate to  shield it all. 
 

Anyways , cool to see as usual and who knows I could maybe copy you or use the knowledge to take a different approach etc.

73 Coupe over the Impreza and just bump out the fenders and quarters with obnoxious looking flares. We’ll see. I’m years away from that project more than likely. But I’d want to keep it thrifty too. 

Edited December 6, 2025Dec 6 by moosens

On 12/6/2025 at 1:57 AM, moosens said:

Sweet! Little at a time.

 

My first thought on the brakes was wondering if anyone has done inboard disks somehow. That would probably take too much money but I am thinking if axles are cut down maybe they could be adapted at the inner ends to accept a disk. Or an existing setup like from a Lotus etc. as an example. 
 

Pardon my freaky thought in the middle of your hard work. 
 

Inboard brakes at the diff, big bash plate to  shield it all. 
 

Anyways , cool to see as usual and who knows I could maybe copy you or use the knowledge to take a different approach etc.

73 Coupe over the Impreza and just bump out the fenders and quarters with obnoxious looking flares. We’ll see. I’m years away from that project more than likely. But I’d want to keep it thrifty too. 

Freaky build thoughts welcome here. I don't think inboard brakes are going to fit on the setup i'm planning, but someone wily might be able to make em fit on a closer to stock undercarriage. I'll probably just be swapping the knuckles to add discs on this one once I've got the suspension set up in the back end. 

 

Did a little more weekend deathwheel work today - took about an hour to get some access panels cut into the bed floor so I can more easily add some gussets to the subframe while it's bolted to the assembly.

The idea here is that I'm going to use them both to reinforce the subframe and it will give me a locating feature when I go to tack this piece into the car so everything lines back up.

The idea here is that I'm going to use them both to reinforce the subframe and it will give me a locating feature when I go to tack this piece into the car so everything lines back up. I've still got to take things in and out a couple times before this becomes a more permanent part of the vehicle. I'll probably weld the panels back in once I'm satisfied with the subframe and suspension towers, as some of these welds I'm planning on leaving only semi-permanent till I've got all the clearances worked out with the coilovers, so I'll be leaving access until I'm sure I don't need it anymore.

 

This last photo looks real scary but in reality it's just me adding four tack welds to the gussets only on the subframe. I'll be removing it one last time to box everything in and hit it with a bit of weld-through primer. 

Folks with a real professional background in automotive engineering would probably cringe at some parts of my approach, but I got everything measured up as even and straight as a mallet and tape measure would allow. I'm honestly pretty impressed with myself at how evenly I was able to get everything to line up with a couple symmetrical features I used as reference points (a couple bolt holes and a few key bends/seams. I find myself repeating the mantra "perfection is the enemy of progress" a lot on this build, and so far (knock on wood) it's working out pretty good. 

Next up I have a fairly short punchlist to get this subframe on the car in a  meaningful way, and then I'm planning on attacking the lateral links, trailing arms, and locating the strut towers. The more I think on it the more likely it is that I'll probably be scrapping more of the Impreza tower than I'd intended. The rust is pretty deep in the driver side tower and the more I stare at the mockup as it sits the more dislike the way it looks. One way or the other I'll figure out something good. Main goal is to have it back on its own four wheels (again) around the new year. We'll see if I make that goal or if I blow past it for some unforeseen reason. 

 

Hopefully I'll have at least one more update before the New Year, but if you don't hear from me beforehand, have a good last few weeks of the year, everybody! 

-M

Edited December 21, 2025Dec 21 by mka

Ok so on the ground by 2026 didn't happen - but i did finally get things to the point where the subframe and diff are now semi-permanently attached to the car. Hooray! 

 

Using the holes in the bed for access I cleaned and tacked in the subframe, using the diff and its sheet metal as a jig to get everything in evenly

 

Once everything was pretty sturdily tacked - I pulled  the jack out from under everything. So far so good! I pulled the CV axles off of the knuckle/wheel assemblies and bolted in the stock lateral links and stacked the tires on blocks to get an idea of where I want the wheels wheels to sit at rest, and this is where the next complication arises - overall things look really good, except the wheels rub on the front of the arches left to their own devices.

I'll need to play with this a little more - I'll either need to do a little bodywork to extend the wheelwells about an inch or two forward, or I may also consider options to move the whole diff/subframe assembly backwards about the same amount, though then i run into other clearance problems in the tunnel. I'll need to spend some time under the car staring at it to figure out which I'd prefer to do. Currently my gut says the latter is the easiest. 

For now, however, this still lets me move forward somewhat with the suspension construction. the more pressing issue at this stage is that the rear track is still several inches wide at the back. I loosely bolted the rear coils in place, and that let me get an idea of how much room I have to cut and move things inboard.

I can almost see the end result - II'll be able to scrap the plan of using the impreza towers and modify the stock wheel wells without too much trouble, even though I might want to reenforce them after the fact. Had I known this prior I would have just cut the tops out, but oh well. Maybe if i do another in the future I can save myself the exploratory chopping. Or hell, even if someone else does this similarly - hopefully I can save you a little trouble.  

  Did a little measuring and this is what I came up with:

Forgive my mixed units and felt tip marker sketch on my mechanics crawler (free USPS cardboard) - but here's the broad strokes: I have a little more than roughly 2" / 5cm of horizontal clearance before the coils begin contacting things they shouldn't. The stock rear lateral links measure about 41cm long bolt center to bolt center, and I'm estimating about 10cm of vertical drop from their frame mounts to the knuckle mounts. if my math is mathed correctly, that means I'll need to shorten the link about 6cm to get the wheel moved inboard the requisite 5cm. I'm going to pull the links all the way off so I can measure them on the ground to double check these measurements - as I've found some adjustable links that would appear to be able to get close to these lengths without much serious modification and if i can do that and save myself a few hours of fabrication, I'd prefer to do that. I've also gotta figure out the trailing arm mount, but that'll come after I figure out the width issue. 

Anyways, that's all for my new years update - until next time kids! 

Oof, the hits keep on coming. Between life happening and that stint where the forums were down - I hadn't had much time to update this, but today I took the time to get things moving a bit again.

Long story short - I decided the simplest thing to do to solve the rubbing problem as it currently exists was to cut the tack welds and shift the whole subframe back about an inch, rather than doing a whole bunch of complex bodywork. My bodywork skills are definitely not my stronger suit, so I figured I'd better make things fit to what's already there as best I can. While this job was harder than I thought it was going to be (I had to cut out a larger section of the bed to get my cutting tools in there), the wheels now sit squarely (loosely) in the middle of the arches.

To continue the spirit of solving a problem by creating new problems to solve, now I have to modify the original rear diff crossmember to make up for the distance the entire assembly has moved. Probably going to knock that out in the next couple days. Basically for that I'm going to cut some chunks out of the existing crossmember , then offset them with lengths of rectangular or square tubing of similar cross section. It shouldn't be too difficult because the stock part is basically a piece of straight U-channel with bushings mounted through it. No weird bends or offsets to be had so as long as I modify it so the threaded holes move directly rearword, it should be a pretty quick fix.

Once that's all done it'll be a temporary modification of the stock lateral links to bring everything a little tighter in towards the frame, then I'll get started on fabricating the strut mounts in the bed, and probably remeasuring everything to see about finding an off-the-shelf set of adjustable lateral links and trailing arms that fit, and then another semi-permanent modification of the rear CV axles to get those back on.

I'll likely need to revisit the wheel arches in some form or fashion, but I'm hoping I can get away with just some good ol' fender rolling. Time will tell.

Edited April 11Apr 11 by mka

On 12/25/2024 at 10:52 AM, mka said:

I'm more than slightly bummed to be ditching the selectable 4wd, but this thing will definitely not hold up to what I'm doing long term. It would be really cool if there were a retrofit or modification for these transmissions to get that to be a feature again but all research I've done seems to point to that being a very expensive proposition at best so AWD it is.

You would need to import a gearbox from Australia that’s a dual range. Easier said than done sadly, but not impossible.

I’m glad to see that you didn’t move the lower lateral arm pivot points - they’re positioned where they are to work with the inner CV joint through the pivot motion of the joint. Move the suspension pivot point and you’ll have issues with the compression and extension of the drive shaft.

I love this build and wish we could do stuff like this over here in Australia - but engineering would be prohibitively expensive to complete to get it road worthy. Other “trick” is to get the original vehicle registered, modify it and either not tell anyone until you’re pulled over and the officer wants to look closer at it…

Part of me thinks your rear subframe and adaptor frame are too wide for the sweet spot that the struts require, you’ll know in good time.

It’ll be a ripper ride once it’s done and one to be proud of!

Keep up the good work, after reading this front to back I’ll stay updated as they come in from now on!

19 hours ago, el_freddo said:

You would need to import a gearbox from Australia that’s a dual range. Easier said than done sadly, but not impossible.

I’m glad to see that you didn’t move the lower lateral arm pivot points - they’re positioned where they are to work with the inner CV joint through the pivot motion of the joint. Move the suspension pivot point and you’ll have issues with the compression and extension of the drive shaft.

I love this build and wish we could do stuff like this over here in Australia - but engineering would be prohibitively expensive to complete to get it road worthy. Other “trick” is to get the original vehicle registered, modify it and either not tell anyone until you’re pulled over and the officer wants to look closer at it…

Quick response to this before today's mini-update: In short, thanks! I'll have to at least peek at an import gearbox, but I'm coming to terms with all time AWD. Not the worst thing to have.

I thought about it a lot and I figured the more i cut up the subframe from the Impreza, the more suspension problems I would have to tackle later, especially the closer I get to the differential. at the end of the day my intent is to keep any and all potential wear items as close to stock as possible so I can buy replacement parts off the rack. Cutting up the subframe is in direct opposition to that directive.

Re: doing a build like this in Australia - I definitely appreciate the distinct privilege I have being able to just "grip it and rip it" over here. I'm curious to what engineering is necessary to have this sort of thing done if it's all above board where you are. I know I've seen at least one or two WRX swaps from your part of the world, although those were the next generation brumby from the 80's.

Okay all - mini update. The diff crossmember adjustments are done.

I dunno what it is with this build but anytime I do any welding anywhere near a thread... no matter how I prep or what covering I do, I always seem to absolutely wreck at least one bolt and captive nut. So replacing that took another extra chunk of time I didn't plan on, but I got it done. Things on the adapter / subframe still need to be perma-welded in, but I'm going to leave them as is until I'm totally certain I don't need to shift things around any more. Once I've got it sitting lightly on the ground again, I'll strip it back down, weld it, paint it, and forget about it while I work on the front end again.

Rear differential now hangs unsupported and centered. Is it super pretty? No. Does it look centered in the photo? No (I promise it is). Is it fuctional as hell? Yes. Do I need to invest in a real fixturing setup? Also yes. Am I going to anytime soon? Strong maybe. I'm also pretty excited that I finally can put my transmission jack away in the garage where it belongs and not worry about it being stolen in the night.

This coming week or so I'm going to start ruin-I mean experimenting on and/or adjusting the stock lateral links to bring the wheels and knuckles closer underneath the car, and then I'll start locating the strut towers. That'll be a wild ride.

19 hours ago, el_freddo said:

Part of me thinks your rear subframe and adaptor frame are too wide for the sweet spot that the struts require, you’ll know in good time.

Re: Subframe and adapter width - your thought is likely going to end up being pretty prophetic, but I have thought about the potential issue before going this route. I have some room to move and shorten things inboard, far more than I would have were I to have kept the Impreza struts and springs. The coilovers buy me at least an inch of clearance towards the centerline and offer quite a lot of adjustability in terms of ride height and length, but If my hunch is correct I'll likely need to do some kind of mild fender flare on the rear end at minimum even with those. It'll probably be some version of Amazon special plastic numbers, but like you said for the struts - I'll figure that out in good time. Fender flares are a minor problem compared to everything else I've set myself up for, so I'll deal with those first.

Oh, one more thing as a small post-script: This may seem blasphemous after all the effort I've gone through to put the EJ in there, but I've fallen down an EV rabbit hole, and I'm considering down the line converting to electric at some point. Thoughts on that?

Edited 11 hours ago11 hr by mka

9 hours ago, mka said:

I'll have to at least peek at an import gearbox, but I'm coming to terms with all time AWD. Not the worst thing to have.

Got the AWD box and if you decide to get a dual range version it’ll bolt straight in place of the single range gearbox ;)

Really though, if you don’t go offroad, you don’t need the dual range. Plus the shipping will be more than the gearbox will cost you!

9 hours ago, mka said:

I thought about it a lot and I figured the more i cut up the subframe from the Impreza, the more suspension problems I would have to tackle later, especially the closer I get to the differential.

My thought on the rear subframe would be to cut the mounts to the body and relocate them to where you want them to be on the chassis rails, maybe even pick up the old diff hanger bolts. Leave everything else so it’s all stock geometry to work with. It’s not a wearable item so once it’s sorted you don’t need to replace it for the life of the vehicle.

9 hours ago, mka said:

I'm curious to what engineering is necessary to have this sort of thing done if it's all above board where you are. I know I've seen at least one or two WRX swaps from your part of the world, although those were the next generation brumby from the 80's.

Well this is the tricky bit. Each state is different in what they require. Here in Victoria you need to find an engineer that’s on the approved list with Vicroads, our vehicle department.

Then you need to meet their requirements and they may change a bit between engineers. I do know that any welding needs to be certified as done by a qualified welder. Brake changes may need a performance test for stability. Using a complete swap like you are makes that easy. It’s the welding of brackets for major components that trips us up here. Same for things like the transmission tunnel grafting. Can be done, but you need to discuss with your engineer about how you’ll do it and they’ll let you know if they’re happy with it.

Of course, the more you modify, the more engineering generally costs - and you want to get EVERYTHING modified on that report, otherwise road authorities can pick you for things they find that aren’t on the list if you’re pulled over and they decide to inspect your vehicle. Doesn’t happen often, but it’s something they can do if they want.

Once engineered, you need to carry a copy of the certificate/report with the vehicle at all times. And further modifications need to be engineered, so you really only want to do it once then enjoy the vehicle!

I heard of one model like yours that someone over here crammed a wrx drivetrain into and got it engineered. Not sure which state they were in, maybe Queensland… My 1990 brumby will end up WRX swapped, but without cutting chassis rails to do it like everyone else. It’s halfway there in a rusty old halfcut with everything dummies up. Engine and wiring loom all works which was a big hurdle with the cut down (my third, first turbo though). I wish my gearbox mount was as easy as yours to make too!

Sorry for the long post! Good to see your progress and hopefully you have it back on all four permanently soon!