1990 EF5 Civic RT-Si (4-door, 4WD sedan) Advice / Transformation Thread

Alright, so I recently picked up a new car for a project which should be a whole lot of fun, and I imagine there may be a bunch of interest from fellow enthusiasts as it is evidently quite a rare specimen. As mentioned in the title above, it’s a 1990 Honda Civic RT-Si, so it’s a 4 door sedan with the 4WD drivetrain from a 4WD Shuttle (“wagovan”) and the DOHC ZC engine.


It is pretty well completely stock, it’s jacked up from the factory to all-high hell, has under 170,000km on the clock and appears to have been garaged its entire life. No rust anywhere in it except for one tiny panel on the back where it once touched a letterbox. I know from experience it is doing very well for a Honda of this age as I am currently losing my ’88 EF3 Civic Si hatch to rust cancer. The only thing wrong with the new sedan really is its automagic gearbox. Unfortunately the old hatch’s time has come and is due to come off the road in 1 months time, hence my decision to undertake this exciting project to make a cool new daily driver while making the best use of any goodies or spares from the old one.


So, the first plans that are causing my initial concerns are how to go about lowering it and converting that slushbox to the real deal. This is my desperate cry for help so I am finally joining a forum and making a thread. I’ll start with suspension:

I eventually want to make it sit really quite low, enough to make it look very sweet at the cost of making speed-bumps quite an inconvenience. Handling, too, is an equal priority. For the meantime, I’d be happy with getting it at the same height as my old hatch (keep in mind it looks high in the pics as it’s jacked up on one side). The hatch has king spring lows in the front, super lows in the back on KYB shocks all round (I believe). After reading that the suspension is very cross compatible between the hatches and sedans, I took one of the rear struts out of the hatch and threw it in the sedan, to find that it actually made it sit ~1cm higher on that side. After some serious WTF moments, I then took out the strut to compare it with the original. As you can see, the spring itself is definitely shorter, but the spring perch on the factory shock is a lot lower to give the suspension more travel with a smaller strut. This results in similar length struts, meaning similar ride heights.


After doing some further reading, people encounter the same problems with the wagons and it seems they are what these different styled shocks are engineered for. Something to do with Honda taking into account that people will be loading up the trunks with more weight... My theory is that they’ve incorporated that suspension in this sedan because of the 4WD system in the rear end. Apparently the front is no different between the EF hatch, sedan or wagon, so my old front struts should be ideal; I just haven’t had a chance to try yet.

I’m concerned with how I am going to achieve my ideal height in the rear while maintaining the good sporty handling I have in the hatch. I’ve looked into coilover sleeves for putting onto the shocks I have, in which case I can just adjust them to the desired height. However if I use those KYB shocks for example, winding them down a couple of inches to the desired height will result in having very little suspension travel. Can anyone shed any light on ideal ways to get around this? Would it be possible to have the KYB shocks rebuilt with the bottom piece of the sedan’s factory shock to shorten its overall length, give it that lower spring perch but maintain its current amount of travel and stiffness?

Now, onto the manual conversion: It uses the same 4WD gearbox as the 4WD shuttles. These are also quite rare thus so are the gearboxes. I have actually managed to locate a parts shop relatively nearby who tells me they have a 4WD manual transmission for a ZC engine, but it is from an EG chassis and has the part number S22. This one in particular is very affordable, too and hopefully in good condition. It sounds like this will bolt on to the engine just fine, but I am not sure if there are any chassis mounts that may not correctly align, or if the output shafts to the rear diff might be in a different place or something. Again, any light on the compatibility of this gearbox would be greatly appreciated.

Another thing I have just read up on is Honda’s INTRAC system. There are a few INTRAC stickers on the new car and from what I have just read; I am (optimistically) gathering that it has some kind of LSD(s) in it. Would this just be in the rear end? Would this potential new gearbox possibly not have that, causing me to downgrade in some ways or cause any incompatibilities?

Please excuse my very long ramble-on and thanks in advance for any assistance you can provide. I hope some of you are as excited to see this car fulfil its potential as I am!


  • RoRoRoRo Wagonist
    i love both cars! the sedan is so cool, i wish north america got those, and your hatch is cleaner then 99% of the hatch's in canada
  • GriftyGrifty Wagonist

    That sedan is very very very rare!! Even is INTRAC which means front and rear LSD's!

    Please please take care of it :)

    Cant wait to see more!

    the S22 is a hydraulic gearbox but will bolt up to the motor, the rear mount will need to be customised though and you will need a cable to hydraulic clutch converter.

    When you do get rid of the auto gearbox I would be interested in the Diff in it :)

    I have a 4WD Concerto and I'm using the EF/ED BC coilovers, not issues to date, you shouldnt encounter any as well. There is a fellow member with a 4WD EF5 who is also using tein super streets with no issues.

    If you can find a manual INTRAC wagon and use the gearbox off that, they are more common.
  • rti intracrti intrac Senior Wagonist
    Intrac is just rear lsd. The 4wd boxes are the same from intrac to non intrac. The only difference is the rear driveshaft
  • GriftyGrifty Wagonist
    rti intrac wrote: »
    Intrac is just rear lsd. The 4wd boxes are the same from intrac to non intrac. The only difference is the rear driveshaft

    Ahh thanks for the correction, I thought it was front LSD as well.
  • VladiVladi Senior Wagonist
    Now thats a cool car!
  • mr_sp33mr_sp33 Wagonist
    Grifty wrote: »
    There is a fellow member with a 4WD EF5 who is also using tein super streets with no issues.

    That's me :).

    Cool car mate, i jizzed my pants when i saw this come up on trademe. If you have any 4wd sedan Q's feel free shoot me a msg.

    You could just use any 4wd wagoo box. Converting to manual isn't going to be fun, make sure you grab the shifter box as well, you wont be able to use your fwd hatch one (difference between linkage and cable).

    Instead of trying to use your 4wd rear shock i'd be just buying an off the shelf coilover. Like grifty mentioned, i'm running Tien Superstreets for ED/EF.

    Hope you treat it well mate! Look forward to this build :)
  • ChaifeChaife Instagram grand master
    man, that is sweet.
  • FrankzFrankz Band Wagon
    Very clean car, looking forward to the progress.
  • PootyTangPootyTang Band Wagon
    Thanks for your feedback guys!
    the S22 is a hydraulic gearbox but will bolt up to the motor, the rear mount will need to be customised though and you will need a cable to hydraulic clutch converter.

    I've spent a couple of days trying to confirm the different information which it looks like you nailed in one hit, thanks. This sounds quite complicated, I imagine I might be better off waiting until I can source a L3 4wd gearbox + shifter box from a wagon (if someone knows of one spare, shippable to NZ, let me know :p). Anyone have any ideas if the pedal box from my hatch will swap over and be compatable? I know it's for a cable clutch as well.

    Regarding my suspension woes, I'm kinda looking at getting these:


    Very affordable, will make use of my good shocks, hopefully almost as adjustable as a full coilover set. I have some nearly brand new rear Tokico shocks, the perches are in the same place as the KYB ones pictured though, of course. I'll patiently await any negative feedback on coilover sleeves (though I am surprised to find quite limited negative review on them so far). I figure with the amount I would wind these down, I would need something like this too:


    That'll only regain me around an inch of travel though - hopefully good enough. Does anyone know what sort of spring rate / stiffness to expect from the GC kit? I want something on the firm side, maybe a little stiffer than the king super lows, but not craaazy hard as this is most likely to be driven daily.

    Once again, I appreciate your interest and any informative feedback.
  • NZ-DB8RNZ-DB8R Moderator
    Honestly, dont bother with coilover sleeves. All well and good for the members from America to use them as they dont have as strict laws as in NZ. To get it at a decent height and still captive you will need keeper springs, will likely need longer extended tophats than that aswell. When you see americans using them and being slammed they are very very uncaptive

    I went through all that with my Shuttle, ended up spending as much as just buying some full body coilovers like BC and even when Id done all that I could it still wasnt as good as it would have been had I just bought coilovers to start with.

    It would be a waste of money importing a gearbox, you should be able to find one in NZ pretty easy and for maybe 1/4 of the price of importing one
  • PootyTangPootyTang Band Wagon
    Long overdue update:

    Progress has been slow, mainly because I did this to my hand...


    But then I finally bought these:


    Then I chucked them in and dialed it down about 70mm from stock at all corners:


    Front is tucking tyre but doesn't rub on the guards except in extreme circumstances. The back looked like it needed to come down quite a bit more but I'm currently limited with how low I can go because of my killer driveway. I dropped it another 10mm at the back (now -80mm from stock) and it still isn't quite level. Here's it chilling with my buddy's AE70:


    With stage 1 complete, I am reeaally happy with how well it handles. Having good firm suspension has really shown to me what difference the 4WD system is going to make. It is strange not being able to drive it fast enough to really test the traction (it sticks like shit to a blanket). I am also very happy to have the height adjustability, because this is all likely gonna need to be changed with new wheels and/or new profile tyres, as well as when I don't have such an unfriendly driveway.

    Time to start looking into stage 2: getting a 4WD manual gearbox and swapping out the shitty thing that's in there now. What an exciting prospect.
  • HaydzHaydz Moderator
    You will come across a 4WD box in pick-a-part occasionally.
  • PootyTangPootyTang Band Wagon
    Haydz wrote: »
    You will come across a 4WD box in pick-a-part occasionally.

    From your extensive knowledge, if I get any manual 4WD box from a shuttle, any idea if it will connect fine with my current rear INTRAC diff? Someone on NZH mentioned that they might have different diff ratios between auto and manual. It's really hard to research this stuff with the parts being so rare :S google aint giving much love.
  • rbwdrivenrbwdriven Senior Wagonist
    I know this is a stupid one.

    Have you tried these guys.


    I've been buying from them for a while.
  • PootyTangPootyTang Band Wagon
    rbwdriven wrote: »
    I know this is a stupid one.

    Have you tried these guys.


    I've been buying from them for a while.

    I did give them a call a couple of months ago and they didn't seem to have anything (or even really know what I was talking about). I guess there will be no harm in trying them again soon though.
  • I guess I owe you guys an update, now that there is another one.

    I took the wheels off my old hatch, cleaned them up, painted them and chucked them on this. I'm pretty happy with the look, considering it may only be temporary (until I possibly get some new wider wheels). These wheels are very very light too.

    The profile of the tyres are slightly lower and because ground clearance on my driveway has been an issue, I needed to raise the front a bit. I raised it 15mm which makes it look a lot more level and I haven't had any issues with guard clearance. I still think it looks nice and low too.



    I tried to take my extractors off the old hatch and fit them to this but I had a bunch of troubles. The bottom section didn't line up with the exhaust under the car and it seemed to touch the sump of the engine, while also poking further underneath the car. I should have taken some pics.

    Next little thing I need to do is to get some new front break pads. Anyone have any recommendations for some suitable for 'aggressive' street use?
  • klumklum Senior Wagonist
    Such a rare car I had no idea they existed I honestly think the ef sedan is the best body for a 4wd setup looking for performance and handling over all as wagons are kind of top heavy subscribing to the build!
  • What do we have here...


    Progress will remain kinda slow, but we'll see how far I can get over my xmas / new year holiday break.
  • PootyTangPootyTang Band Wagon
    Hey guys,

    I'm having a bunch of trouble finding the shifter assembly and cables for my gearbox swap. It is seeming to be impossible to find the assembly from a 4WD shuttle or another RT-Si so I am now wondering if I might have any more custom options.

    Does anyone know what it might be like to try and custom fit something along the lines of the following kind of things?



  • spinoutspinout Band Wagon
    Preludes have similar shiftboxes and are probably cheaper
  • shenrieshenrie Council Member
    ^^^ as well as 90+ accords and crv's. when i converted my wagon to crv drivetrain the shifter cables were really close to be exactly the same as the rt ones.

    oh and badass car man. i freaking love it. one piece lights, raised cowl, rt4wd...all the goodies i love from non usdm sedans.
  • So I pulled out the engine and gearbox from the old ef3 hatch:


    I pulled out the clutch and noticed it is different to the one I need for my 4wd gearbox. Here is a pic of the flywheel and pressure plate that came with the 4wd gearbox. Sitting in the pressure plate is the clutch disk that came with it, and sitting on the flywheel is the clutch plate I just pulled from my ef3 hatch:


    So it looks like I'm in need of a new clutch kit of the higher diameter and lower spline count (20 not 21). I should have a heavy duty one on the way very soon.

    I've had some other worries with it for a little while, which have recently gotten worse. Sometimes during hard cornering, it gets a little unstable over bumps and darts around a little randomly. There are occasional shakes, noises and shit when just driving it at certain speeds even on a straight smooth road but this is all intermittent. I still haven't had a wheel alignment done since lowering it, and considering how big the drop was, this is probably a good idea. So I'm getting that done this weekend.

    There has also been a bit of a drivetrain whine that has been getting slowly more noticeable. I was just hoping that it was the gearbox and not the diff or driveshaft because then it will just be getting replaced. On Tuesday I was driving along and something made a little bit of a bang, a bunch of shit on the car shuddered for a fraction of a second and it kinda lurched forward (slowing down) very briefly. It was very instantaneous, and then it happened again another 5 - 10 meters later so I slowed down and pulled over. I was thinking it could've been some suspension or steering component coming loose and a wheel going wonky for a split second, the steering felt a little bit funny as I pulled over but I think I might have just been imagining things. I realised that it kinda lurched from all 4 wheels so it may more likely be drivetrain, it just doesn't make sense to me that it happened 2 times in quick succession, but not close enough together to be every revolution of the wheels or drivetrain. After checking all corners that the wheels and suspension felt sturdy, I completed my drive home with no issues re-occuring. Thinking on it now, would the engine momentarily losing spark cause it to lurch very briefly but quite aggressively at that kind of low RPM (I'd guess around 2,000)?

    Man I hope it's the gearbox.
  • rbwdrivenrbwdriven Senior Wagonist
    Stupid thing.

    Did you pull your distributor cap and check the rotor button tightness?

    EF's prone for that bloody button suddenly getting loose and walking off.
  • So I can get the shifter assembly and cables for a K20A gearbox, which I guess is from a newer (2001) Type R Civic or Integra. From my understanding of the shifter's basic mechanics, it should be quite universal, I just have no idea how it will bolt to the chassis.

    I'm just slightly concerned about the cost as it will cost me around the same or maybe even more than what I paid for the gearbox, but sometimes that's just the way it is.

    I have some new goodies that have arrived that I'll have to get a picture of for you guys sometime. There will also be some other good goooood goodies on their way next week, so stay tuned.
  • I would honestly keep searching for the correct shifter, i dont think its cost effective to modify the K20 one to work + you will still need to seal it at the firewall some how.
  • So here are some new goodies:



    New HD clutch and pressure plate. Thankfully I got the correct flywheel with the gearbox.

    Still hunting for the right shifter assembly.
  • PootyTangPootyTang Band Wagon
    Looking like this is going to be quite a fun project:


    ...when I finally get properly into it.

    There was a bunch of other cool stuff in the kit not included in this picture!
  • GriftyGrifty Wagonist
    aww yeah!!!
  • GriftyGrifty Wagonist
    I might have a shifter for you, will let you know by today.
  • PootyTangPootyTang Band Wagon
    Awww hell yes.

    I have had a couple of possibilities from a couple of different people in the States, but all of those options would cost me a fair bit more than what I paid for the gearbox. Only having to ship out of Aus should be far more ideal.
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