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Different weights/viscosity definitely affect handling! There is a big chart online someone put together that breaks down the actual viscosity of different brands and "weights" (which is apparently a pretty arbitrary thing) of shock oil. In the Subarus we used the Fox JM2 oil but it is expensive so recently we've been using Sunoco Sunvis 1015 or Glacial Blu by Kendall. Those three are fairly equivalent. In your specific case I really don't know.

I've played with these, swapped gearing, diffs, etc. many many times over the decades (I've posted a lot of it here, search for my posts. Although most of the photos are probably gone). I have a little information in the Retrofitting FAQ. Here's a "quick" overview. RX is the ONLY EA-series transmission with dual range and FT4WD. It is also the only one in the US Market. I have heard of an EJ series dual range and FT4WD (with locking, not AWD) overseas, but I'm really not sure. Also would create it's own headaches with an EA engine (I assume that is what you're running just from context) RX has 3.7 axle ratios, 1.19 low range and .871 5th gear Non-RX EA82t FT4WD ('87.5+) cars are single range, 3.7 and .871 XT6 has 3.9 axles, no low range and .780 5th. PT4WD D/R 5 speeds are 3.9 axle gears, 1.59 low and .780 5th (I believe '85-'87 turbo PT4WD cars are the same, but I'm not positive). Might be possible, but the lower transmission gearshaft is different between part-time and full-time 4WD (FT is 2 piece with a pinion gear running inside of the transmission output shaft, PT has the pinion gear one and the same with the output shaft. The the low range gearset is part of the input shaft. You can swap gear ratios, but you have to start with a dual range input shaft and case. So without actually having an RX transmission to start with, you'd be using the input shaft from a PT4WD DR and the output shaft from the XT6. Since the drive gears for 1st, 2nd and reverse are part of the input shaft, you'd have to use the PT4WD driven gears on the FT4WD output shaft. I wouldn't bet that that would be interchangeable, but maybe. The center diff housing from the XT6 will not have provision for the low range linkage. Not a huge hurtle, but something that has to be addressed nonetheless. IMO, if the gravel is loose enough that you're spinning a front tire in FWD, than it's loose enough to run 4WD. I had an '86 wagon that was stock except the EJ22 and rear discs, I used 4WD when the ground was damp otherwise it would just spin away everything. Also, keep in mind, when the center diff is unlocked on a FT4WD, you have zero traction devices. If you hit the throttle hard in a turn, you will still spin up the front tire just like you would in FWD. I was so disappointed with the RX box in my Loyale. Even that tired non-turbo EJ22 could smoke the inside front tire coming out of a turn on dry pavement, and I was running 215/45r17x8+48s with High Performance All Seasons and EJ knuckles for better Akermann angle and camber. On my '88 XT6, I dropped phase 1 EJ internals into the XT6 front case halves. Better gearing (4.111 axle gears, but .738 5th, so lower rpm on the highway), and the center LSD is light years better than the open FT4WD. I had started combining all of this to make a dual range with 4.444 axle ratios, 1.59 low range, EJ AWD center diff, and a clutch-type front LSD, but that particular front LSD does not clear the low range set. I ended up scrapping the whole project. The front LSD might find it's way into the split-case 6 speed destined for my H6 Baja project, though.... Experiment if you like, but I think you'll be very sad with the results, especially considering the amount of work to get there. It'd be so much easier to EJ swap, then you have the torque where you don't need the low range, and viscous center diff.

Sure will. I have another unit on order so I can create the step-by-step instructions and also take some better detailed photos. I plan to offer the bracket adapter, dust cover and a small hardware pack at a nominal fee so people can buy their own SERA484-10 TPS and then modify/install it themselves. It's hard to see the bracket in the image below but it is medium gray in color and wraps around the TPS. Red arrows in the photo point to the bracket and longer screws are required but easy to find. The wiring sounds confusing but is actually straight forward. Since the TPS is reversed (but then installed upside down) the wires go to the same A,B,C &D positions as before. I'll post up some more details soon. I 3D printed the backet using ASA filament, which is one of the best for high heat areas.

Wow! This is great news. I've been trying to sell my 87 GL-10 Wagon, as is, with the TPS missing. I've had 4 or 5 people want it. But as the OP of this thread and in the spirit of full disclosure, I've pointed them here and they each lost interest. Would you be so kind as to post more details and photos of this solution, including the mounting bracket you created?

No, not yet, just arranged the wire transfer and shipping is being arranged currently. Bill Rigsby - Florissant, CO - 8,213 feet 1982 Brat

Have you received it yet?

I'm quoting my own post from 2025 because I have since revisited the question of using a SERA484-10 4-wire throttle position sensor as a $30 alternative to the OEM TPS that, when available, sell for over $300 (if you are lucky enough to find one). It's not a quick PNP solution but it is working for my 1987 EA82 DL wagon with the SPFI engine and not that difficult to install. The functions of this substitute TPS are all a mirror image of the OEM part and it even had the Hitachi logo on the plastic case. By mounting the TPS upside down, and creating a new mounting bracket, I was able to make it work quite well. I have about 150 miles on it so far with no issues. The idle switch is still adjustable and functions properly. The resistance range at idle and full throttle are easily within the range of the factory service manual recommendations. I will clean up the wiring in the near future but for now, I have simply made a set of jumper wires to go between the old TPS plug and the new TPS body as the 4-wire plugs are not compatible.

They do have a very extensive manual, was not familiar with that site thanks. Bill Rigsby - Florissant, CO - 8,335 feet 1982 BRAT GL

You need to study the pinion shaft setup as this is the key to a conversion like that. If the PT4wd gearbox has a pinion shaft that floats on the pinion shaft and is independent of it, then they’re interchangeable. I haven’t fully investigated this but I believe the PT4wd’s pinion shaft is press fitted with the lower gearset. This is why you can use an EJ gearbox to make a dual range AWD locking centre diff gearbox that mates directly to the EJ engine (like I did). The nasty way to make a single range AWD LCD gearbox dual range is to find an RX turbo PT4wd gearbox with the same gear ratios, pinch the upper gearsets with the dual range setup and fit it with the lower gearset from the AWD LCD gearbox. ^ insert potential gear whining followed by potential early retirement of one of those gearsets. But you’d have a dual range LCD AWD gearbox..!

I have the physical book somewhere, but yeah, all the scans I've seen are missing those pages. Does https://charm.li/ have what you need?

A couple forum posts I read said the XT6 came with a single-range locking center diff box with 3.9, and if you can find one of those too, you can make a dual-range 3.9 box, and have a spare center diff. I wonder if you even need an RX box or if you can mix-and-match a single-range full-time with a part-time dual-range front half...

Finding one is the challenge - and one without a shagged centre diff. Finding a 3.9 is the unicorn. Hence why my box was put together with a modified pinion shaft for 4.111:1 diff ratio. From memory a 27 tooth speedo drive pulls the speedo back in perfectly with 27 inch diameter tyres. Again, from memory this came from an early Liberty gearbox - a gen 1 series 1. Need to find a suitable locking AWD gearbox first…

Wondering if any one has a PDF of the 1983-Subaru1600 1800 ENGINE AND BODY SERVICE MANUAL, that is complete? All of the copies I find on-line starting at page 765 have missing pages and starting at page 775 every other page is black to the end of the book? Bill Rigsby - Florissant, CO - 8,335 feet 1982 BRAT GL

The harder part might be finding more than just a pic of one... and then figuring out how to get 3.9...

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! 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. 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!

That’s the one!

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. 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?

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.

I found a pic of a ft dr... it has both a vacuum pod cable and a manual lever.

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!

Hi all, I'm putting an 84 Brumby back together, has anyone got a diagram of the different lines in and out of the tank/vapour thing? I believe the fuel out to the engine come off the front of the tank, but I'm a bit lost how the return and vapour lines connect around the fuel tank. Thanks, Simon

Hey Todd, I was meaning to ask about what oil you used when you serviced your struts - then the forum went down. I have a set of MY front struts that are (were, I pulled them apart!) oil filled. What I didn’t think about was what oil I’d refill them with and that project sat on pause. Keen to hear your thoughts on this and how different weights/viscosity affects handling. My brumby will end up EJ’d with a water to air intercooling and AC if that’ll make a difference. Regards Bennie

G’day @bushytails The L series AWD locking centre diff gearbox came in the RXII coupe, some XT4s and JDM GT wagons. I’m unsure about the XT6 - we didn’t get them here, infact all of these models except the XT4 were personal imports. How to tell them visually apart from the single range PT4wd gearbox with the vacuum actuator to engage the rear drive: this PT4wd single range gearbox’s lever to engage the rear drive is arm above the pivot point. The AWD locking centre diff gearbox is the opposite - the arm is below the pivot point for the locking centre diff engagement. I believe the dual range version will have the rods passing through the rear housing like the DR PT4wd gearbox. The AWD gearbox comes in single and dual range. Pick the one you want as it’s not easy for you to swap it to dual range without another dual range AWD gearbox (EA or EJ). The 3.9 ratio is out there from what I’ve heard, it’s hard to find. Mine was a 3.7 ratio. All of these dual range AWD boxes are 1.19:1 low range. The 1.59:1 transfers in without any issues, it’s a direct swap - need a donor NA dual range PT4wd gearbox. The EJ AWD gearbox pinion shafts are too short. I heard of a bloke that modified two of them to make one pinion shaft for the L AWD locking centre diff gearbox to get 4.44:1 diff ratio - to do this with the good L series low range requires the crown wheel to be shaved to clear the low range selector ring and gearset. I have not seen pics or videos of this done (the double EJ pinion shaft to make one L series AWD pinion shaft). From my understanding, L series PT4wd gearbox internals do not swap over to the AWD version, other than the low range. Everything will physically fit but it’ll become a part time box that requires the part time rear housing as well. My gearbox is made of EJ parts (drive gears and front cases) and the L series AWD bits for the locking centre diff and 1.59:1 low range. Ultimately if you’re on dirt that’s somewhat loose, you want to lock your centre diff, especially if EJ’d as it’s very easy to be spinning the front wheels faster than the rear, over working the centre diff that will lead to its destruction. You could be better off sticking with the PT4wd dual range box, the AWD is only worth it on solid surfaces. ^ PT4wd in the foreground, AWD in the background, you can see the locking lever on the side here with the pivot point above the arm. I don’t have any better pics than the above sorry. I believe the dual range AWD gearbox is fitted with the same rod looking setup in the background of the gearbox as the PT4wd gearbox. My dual range AWD gearbox is built from a single range box originally, so my rear housing lacks the rods that I believe pass through the rear housing for the low range dedents/position retainer setup. Make sure you get the vacuum actuator and it works, plus the matching vacuum switch solenoids too, or have access to them. The single range PT4wd gearbox units work fine with the AWD box ;) I hope this helps.

Rob Allen may offer some insight. Wizard of the RX ;)

Would be for 1975-79 4WD Wagons and 1977-81 Brat 1600 EA71 Top starter location is the give away. They’re fairly plentiful for their age. I scrapped and gave away several and now still have at least two sitting around.