How To Build A B-Series AWD Honda Civic
Posted by Matthew Marks on 12th Nov 2024
Today, we will help you build a full AWD conversion setup for your Honda Civic! We will review the OEM and aftermarket parts you need, the different brands that make the various parts, and everything in between.
For this article, I'm going to be referencing our own AWD Honda Civic EK B-Series build, but all of the parts are very similar for an EP3 or DC5; you will need to use MK2 CRV parts rather than the B-Series MK1 CRV parts as a base.
You can check out our build, where we went from FWD to AWD in around 24 hours. The video is below and whilst you're there, please subscribe to our YouTube channel for more car build progress! We will do weekly videos on the build and try to show every step of the way (including the failures).
For this guide, we will go from the front of the car to the back, starting with the gearbox and ending with the differential and driveshafts, and explain why we used all of the parts we did. Let's start with all the OEM parts you need for your build.
Oem Honda CRV MK1 Parts
So, as we are UK-based, we will use the Honda CRV MK1 as a base for all the parts here. They are easy to access, and you can pick up the running gear very cheaply. We found ours a few years back on the Facebook marketplace for around the £400 mark, which was a bargain!
If the Honda Wagovan were more readily available in the UK, we would buy it, as according to American sources, it tends to take more power stock than its CRV counterpart. We will also use some Freelander parts here, as they will take more power (such as the prop shaft) and are the best off-the-shelf viscous coupler.
So this is the list of parts you will need to grab from a MK1 CRV and/or Freelander:
- SBXM B20 Gearbox
- Transfer Case
- CRV Shifter Cables and Bracket
- CRV Shifter
- CRV Propshaft
- Freelander Propshaft and Viscous Coupler
- CRV Rear Differential
- CRV Rear Driveshafts
- Civic Rear Callipers, Brake Pads and Discs
Optional
- S9B Gearset
- Honda CRV rear trailing arms (if you want to use the 5x114.3)
Gearbox Build
Now that you have gathered all the parts, you can use the stock CRV gearset or a longer-ratio OEM option such as the S9B, the longest-geared B-Series gearbox from the factory (that I know of).
Considering that we were around 500whp (and I'm assuming you are also turbocharged), we decided that the CRV gears were too short, and we wanted to hold the gears for as long as we could for power delivery, so we combined S9B and SBXM gearset parts.
If you are looking for an S9B gearbox, you will need to find a Honda Civic MB6 breaking; again we found ours on Facebook marketplace cheap for around the £400 mark, as the shorter geared gearboxes such as the S80 are more popular (and more expensive) for naturally aspirated applications.
Also, the CRV 1st-2nd gear selector is incredibly weak, but luckily, we also have the option to fix that later on! The CRV differential is also an open diff, so we added a wavetrac AWD differential into the gearbox and a Speedfactory FWD2AWD conversion kit.
The video below shows our gearbox build, in which we install both gearsets together and build the gearbox from scratch.
So first, we will run through all of the parts we used in the gearbox build, including the gearsets:
- OEM SXBM Gearset and housing
- OEM S9B Gearset
- Speedfactory FWD2AWD B-Series gear conversion kit
- Wavetrac BAWD LSD
- Synchrotech B-Series carbon synchro set
- Speedfactory BAWD detent springs
Now, let's move on to how we use each part in combination with the others. The CRV gear set was never designed for high horsepower or RPM.
With a vast gear spread between 1st and 2nd and the stock rev limit of around 6700rpm, you will get a much better drive and feel from an S9B gearset retrofitted to the BAWD gearbox. This is where the S9B gearset and the Speedfactory FWD2AWD kit come in.
Speedfactory has developed a billet shifter fork and shim kit, which allows you to use the 1-4 gears from the S9B to have the longest ratios possible and remove the weak 1st- 2nd shifter selector fork.
This kit doesn't require machining, making it an excellent option for easily retrofitting this gearset. However, it requires the Input shaft, hubs, sliders, and synchros from the FWD gearbox, while the countershaft and ring gear must be from the AWD gearbox.
Then, you remove all the gears from both stacks and rebuild them using the 1st-4th gears from the FWD gearset and the 5th gear from the AWD gearset.
There is also an option to use this FWD2AWD kit for a PPG gear set, but this was more than we needed for 500whp.
As for the differential, the stock CRV gearbox will come with an open Differential, so we decided to go for the Wavetrac BAWD LSD. At the time, this was one of two options on the market, the second being an h22 LSD, which you need to machine and shim, but we opted for a full, bolt-in option.
Don't worry if this sounds daunting; the Speedfactory kit will come with instructions on how to do all of this and where to put the shims, and if you need to, reference our gearbox build above.
AWD Engine Mounts
The next part on the list would be to get upgraded engine mounts. If you're already turbocharged (which I'm assuming you are), you will know that when you come on to boost and let off, the engine will rock more than OEM engine mounts can handle and can often split.
This is where you generally upgrade to an aftermarket engine mount kit option, such as Hasport, to give you a stiffer engine mount and remove the engine from being back to rock back and forth.
If you build an AWD, you will need specific AWD engine mounts, as the CRV mounting positions for the gearbox and rear subframe are slightly different from the OEM mounts.
We went with Hasport BAWD 70a engine mounts for our build, but the most significant bits here would be the gearbox bracket and rear bracket, as they allow you to mount the gearbox and sit it in the correct position for the transfer case, etc.
The gearbox mount differs slightly from its FWD counterpart, so you must choose a specific AWD mount set to ensure everything fits.
Ensure you get the correct AWD engine mounts for your chassis and subframe. This shouldn't cause you any problems. The fitment was incredibly tight on ours on the rear engine mount and bracket, but everything did align correctly!
Shifter And Cables
You could take two paths, and they both depend on your budget. The first option would be to use all of the CRV OEM parts, which would line up and be able to be directly bolted into place.
There are a few disadvantages here, though, with the main one being the age of the parts. The older these parts become, the more worn they are, and the more it is worth going with a brand-new aftermarket option.
Short Shifter
We decided to go with an aftermarket short shifter to get the most out of the AWD system and make the build more fun.
So we decided to go with a Hybrid Racing Honda Accord CL7 shifter and matching base plate, as most aftermarket B-Series shifter cables have been designed specifically for the CL7 shifter.
To mount this, we had to modify the tunnel, though. As the car was originally an automatic, we flattened the hole in the car where the shifter sits above, drilled some holes, and attached the base plate with the supplied hardware. The shifter then bolts to the top of this for a clean look.
Shifter Cables And Firewall Bung
Now that we have sorted the short shifter, it's time to move to the shifter cables. At the time, the only option was the K-Tuned BAWD shifter cables, which come with a bracket that bolts to the gearbox and allows the cables to sit at the perfect angle.
Since we bought all of our parts, Hybrid Racing has now released a BAWD shifter cable kit, but we have yet to swap over as the K-Tuned version has not caused us any problems.
We could have also gone with the OEM CRV option, but the cables we initially had were stretched, so we decided against it. Plus, the aftermarket cables generally have replaceable spherical ends, which is a bonus and gives a better feel than the OEM rubber bushes.
Now that we have chosen the shifter cables, we must decide how to pass them through the bulkhead to connect to the shifter. There are two options here, and in the past, we have taken both routes in separate cars. It mainly depends on what you're doing with the heater box.
In our original build, we removed the heater, as the plan was always to go with something aftermarket, such as the T7Design 400w fully electric heater. In this case, we could use the original hole that the heater passed through the bulkhead.
In this build, we decided to retain the OEM heater for the time being, so we drilled a hole in the firewall on the passenger side to the correct size of the K-tuned shifter cable grommet. This allowed us to use the rubber and remove the chance of the shifter cable rubbing against the metal.
Now that the shifter side is all sorted and you have chosen your shifter, cables, and transmission bracket, we can move on to the AWD system.
Transfer Case
So, for the transfer case, we have decided to go with the stock case for the time being, but the more power we run, the more likely the case or gears are to break.
There are a couple of options here, such as the Speedfactory billet B-Series AWD transfer case, a complete like-for-like replacement that will house OEM or aftermarket gears when correctly shimmed.
For the transfer gears themselves, there are options out there now for upgraded hypoid gears, which are much stronger, but we won't delve too deeply down that rabbit hole in this guide as this is more to help you build your first AWD system.
Prop Shaft
You will now need to decide which propshaft you will use. In our case, we wanted to use the viscous coupler from a Freelander to allow the power to gradually transfer and reduce the risk of snapping anything in the drivetrain.
Because of this, we opted to get a custom propshaft made. We used the ends of the CRV prop shaft to match the bolt pattern on the transfer case and rear differential and mated this to the Freelander prop shaft.
We also upgraded all of the U-joints, as they are also prone to breaking. A great option is to go with 1310 U-joints, regarded as one of the best ways to easily upgrade your prop and take outstanding power.
As a very easy off-the-shelf option, S1Built now manufactures the 1310 u-joints, so you can buy them and bolt them directly on!
As mentioned earlier, we decided to use the factory freelander option for the viscous coupler. Still, there are now options for brand-new versions, such as the S1Built viscous, a great bolt-on option with brand-new carrier bearings.
As our viscous coupler and carrier bearings were in perfect condition, we had no need to upgrade to a brand-new one. Still, upgrading has an advantage, such as choosing the viscosity of the fluid inside the viscous coupler, which will change how quickly the power is transferred. When building your first AWD, the OEM one should be fine.
Viscous Coupler Mounting
Depending on which viscous you have decided to use, you have a few options for mounting it. For an off-the-shelf option, you can use the Innovative viscous coupler mounting brackets, which are a great option, or make up plates, as we did.
We used thick 4mm steel and welded a cross-section to allow the carrier bearings to be mounted. We also slotted them slightly in case we had to adjust the angle of the prop shaft in the future.
The choice between these options is down to you, and it depends if you feel confident fabricating, or if you prefer a bolt on option.
Rear Differential
We opted to use the stock CRV differential and housing for the rear differential, as we knew this would match everything else in the setup, and we would not have to work out gear ratios, etc.
We are now running a viscous in the system, though, so we did not need the clutch packs in the rear differential. The prop shaft runs to the rear in the stock system, and the fluid inside the rear differential will engage the clutch packs.
The viscous coupler now controls the power to the rear, not the clutch packs, so we no longer need these. Plus, the fluid will generally boil when you run more power than stock, so from a longevity and grip standpoint, eliminating them also made more sense.
cause of this, we removed the clutch plates and installed S1-Built locking plates in the rear differential. These plates make it much easier than the conventional method of pinning and welding the clutch packs. You just replace the clutch plates with the locking plates, and you are good to go!
If you wanted permanent AWD, you could remove the viscous coupler from the system, and every wheel would constantly be a driving wheel. However, you risk binding, so it is much safer to combine the viscous and the locking plates.
Rear Differential Brace
Before we go any further, as a quick note here, you will have to remove the OEM fuel tank to make room for the rear diff, but we will explore the options of aftermarket fuel cells later in this guide.
It might also be worth removing the OEM fuel lines. Although you can use these, you would have to convert them to whichever fuel tank you're using, and at that point, you're better off just removing them and opting for something more versatile, such as AN fittings and hose.
Now, we need to decide how to mount the rear differential.
As we are using a Honda Civic EK as our base, we had multiple options for this, including Innovative, S1Built, and Hubcityperformance.
At the time, we went for the most accessible option, which was the Innovative AWD rear differential mount. Everything has been designed to make it very easy to bolt up the rear differential and for it to sit at the perfect angle.
We did have to modify the chassis a bit, though, to make everything work. First, we couldn't mount the rear differential without notching the subframe, so we cut a section out of that, folded the tabs up, and welded it back up.
Without doing this, the back of the differential housing would have nowhere to sit, and you could not physically get it to sit underneath.
Once done, you must weld plates on either side of the brace to get a solid mount to the chassis. Innovative includes a Rivnut kit to allow you to do this without welding, but we went for the welding option as it seemed a bit more permanent and more substantial.
Lastly, you may have to hammer up the boot floor slightly to make the diff fit correctly in line with the brace and prop shaft. You only need a very slight amount, but it is always worth doing, as the prop/diff will have to sit at the perfect angle to not cause any problems.
Rear Trailing Arms
Now we move on to the rear trailing arms, which are incredibly important as this is how you will connect everything in the system to add drive to the rear wheels.
There are a couple of options here, and it would mostly depend on the stud pattern you are going for or how much you want to spend. So, for our build, we opted to go with the DIY S1Built kit, which includes the gusset plate that needs welding in and a hub adapter to fit our bolt pattern and accept the driveshafts.
At the time of writing, this is still the cheapest option, but it is not a direct bolt-on. You need to cut a hole for the hub adapters and weld in the rear gusset plates. As it needs a bit more work, this isn't a beginner-friendly option, but it would be the most cost-effective option.
If you want a more bolt-on option, they now offer stainless steel rear trailing arms that replace your OEM trailing arms. These are direct bolt-ons with no modification needed and also come with trailing arm bushes, etc.
They are also available in multiple stud patterns such as 4x100, 4x114.3 and 5x114.3, so you can match the wheels you already have or the stud pattern at the front of the car to make wheel choice that little bit easier.
Both options here will work; it depends on whether you prefer to save some money and weld the parts or spend more and get a full bolt-on option.
In terms of calipers, they are designed to be able to bolt on OEM calipers, so whether it's a 242mm or 262mm rear setup, providing the discs are the correct PCD to the trailing arms you have chosen you can fit them like a stock setup.
You will also need to match handbrake cables to a rear disc setup, but you may already have this if you convert from a setup that already utilises rear discs.
Rear Shock Brackets
The rear shock brackets are the next part you will need before fitting the driveshafts. These brackets fit between the suspension strut/coilover and the rear lower control arm, moving the shock over slightly to allow room for the driveshaft.
If you do not use these brackets, the driveshaft will rub the suspension due to the hub's alignment with the rear trailing arm.
These are incredibly simple to install by removing the shock and inserting the shock bracket.
here are two options here. The first is the stainless steel box section S1Built shock bracket, which we opted for, or they now offer a revised billet version. Instead of the coilover fork sitting over the shock bracket, the new revised design replaces it and slides over the bottom of the coilover.
The only note about this second option is that you would need coilovers with a removable bottom sleeve because you have to remove this to make this option work.
Now that you have nearly every part you need, the last thing on the running gear list is the rear driveshafts themselves!
Rear Driveshafts
Now that you have mounted the rear diff, we can move on to the driveshafts. For the front, you can use any B-Series driveshafts provided you are using the correct hubs to match the spline. On the rear, it would depend on which trailing arms you have chosen from the section above.
If you went with the S1Built example, they will accept any CRV/Wagon 23-splined rear driveshaft. As we were using all CRV parts for this, we ended up using 2 x short CRV driveshafts. From the factory, the CRV rear differential is mounted slightly off-centre, making one driveshaft longer than the other.
As the rear diff mounting kit locates the diff in the centre, the only way we could make it work correctly was to use 2 of the short driveshafts.
We ended up going to insane shafts in the end, and so far, so good. We actually bought four of these, as one of our customers was doing the same swap at the time. After installing everything, you should now have a fully working AWD system!
There is nothing tricky with the rear driveshafts; they are installed as any other driveshaft would be.
Fuel Cell And Lines
Now, we need to get the car running, and the first thing on the list is a fuel cell. As mentioned earlier, you have removed the stock fuel tank and lines, but we still need to find a fuel cell and make up lines.
There are three good options here, again, all money-dependent. The first one is to go with something such as a
Nuke Performance fuel cell, which you can mount in the boot. As they have an inbuilt CFC swirl pot unit, you can mount the pumps in the tank, which makes for a much neater install.
The second option is to go with a cheaper fuel cell, external swirl pot, and external fuel pumps (which we opted for in the first build). I'll add the video below here in case you want to learn how to build this entire system from scratch.
The last option is to go with a specifically made fuel cell that would fit underneath the car, such as a custom-fabricated option or something like the FCS fuel cell, which fits neatly underneath the car and removes the need for mounting anything in the boot.
once you have chosen the type of cell you need, you need to make up AN lines or some fuel line to feed and return from the fuel rail. If you need help with how to make AN lines, we have a guide here that goes through all of this in depth.
If you prefer to build the system yourself, we have a video below of the external fuel cell and swirl pot setup in our last AWD build.
Exhaust
The last item on the list before you can start driving the car is the exhaust. If you've already researched this system, the exhaust is likely the most challenging. It will have to be fully custom, as you have now taken up the whole tunnel, which the exhaust would usually run down with a prop shaft and viscous coupler.
So, there are a few options here. You can either run everything out of the bonnet/side exit, which in drag applications is acceptable (or area, depending on the local law). In the UK, we cannot run the exhaust out of the bonnet due to the regulations surrounding this and the need for a catalytic converter.
If your application is solely drag racing, then you don't have a huge issue here. Cut a hole in the bonnet and send it (haha!).
But for road use, it's a bit trickier.
We did actually find a great video which outlines the entire exhaust system from front to back, and this is the route we are going to go with our build (currently in progress) where you run the exhaust down as usually just past the anti-roll bar, then cross over to the passenger side, and oval the tube to be able to fit down the little gap in the chassis (this is why we also moved the brakes lines to the other side).
From here, you can add silencers or anything else you need to add before exiting at the back.
There are a few things to note here. Firstly, on the passenger side of the chassis, you will encounter brake lines. To counter this, we had Hel Performance come down and measure up some custom lines, which we can move to the opposite side of the car so we don't boil the brake fluid.
The next thing to consider is that if you went with the fuel cell mounted under here or were thinking of running fuel lines here, you would either need to move it to the opposite side or figure out where you can physically run everything.
The main thing here would be to forward-plan the brake and fuel lines to ensure this doesn't become a problem, so hopefully, you have read down here before starting to order or fit anything!
Once the full exhaust is all made up and ready to go, you can finally start the car and watch that all-important first turn of all four wheels!
Conclusion
So now you should know everything you need to build your first B-Series AWD Honda Civic! Although there are a load of variables here to account for, I have tried to cover everything I can think of.
If you think I've missed anything or you need help with any of the steps or parts here, please comment below. The more in-depth the guide is, the more chance we have of helping someone else build their first one.
Alternatively, if this has helped you, please let us know below or tag us in your videos on social media, as we would love to see them! @exoracinguk
Thank you all for reading, and if you would like to check out any of our other related articles, which may also be helpful, I'll link them here: