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Loadbane

Modular VW based build

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Hi, I'm planning a project build, a VW bug sleeper with a mid (NOT rear) mounted EJ2X engine with a turbo (probably an EJ2X), manual transmisison and I have a few questions, mostly to do with the transmission, differentials, and axles.


My dream build stared as a typical VW sleeper with a turbo EJ engine. Nothing new there. From that point I figured to set it apart and remove the need for reverse cut crown and pinion gears, I'll have the engine mounted in the middle, where the rear seats will go.

Engine selection is flexible, power target is around 300hp at the flywheel. EJ25 I think would work?

My understanding is that Subaru has a 2wd conversion kit that eliminates the rear driveshaft. From here my initial concern is in the Subaru front diff (at the rear in my build). Will the front diff handle the power by itself? Can I use the front axles with the rear hubs or the rear axles with the front diff?

Now things get a little, let's just say ambitious.

I'm thinking of custom A-arm suspension with variable coilover mounts to quickly turn it into a buggy. (Move the mount inwards, get better travel, more height, softer effective spring rate. Fix the camber and put big tires. That kind of thing.).

The concern here, as above is in the axles. Strength of whichever I can use.

And here is where it gets a little crazy.

The transmission was designed for AWD, and built as above I'll have an eliminated rear driveshaft. Is there any reason I can't use it? Say, remove the 2wd kit, and hook it up to a bolt on subframe with a rear diff. Now the car has 6 wheels and space for a  truck bed/camper/what have you. Would this work? In this setup the rearmost wheels may not have brakes. I'll see.

Is there something preventing me from removing the 2wd conversion, putting in a VCD center diff, and attaching a rear diff via a chopped down driveshaft? Yes this will be a ridiculous 4x6 extended bug.

Now a risk of sounding totally crazy

Based on that idea above, instead of a VCD and driveshaft,

Can I put a solid center diff and a propeller?

Some pontoons for buoyancy that kind of thing, make an amphibious Herbie type crazy build. Similar to how guys in New Zealand made an amphibious Impreza most likely.

Thanks for reading all the way to the end, and apologies for possibly sounding totally out of my mind.

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It is crazy, but all do-able, given enough time and fabrication/engineering

 

Almost any turbo Subaru engine is capable of 300 crank hp with a decent tune (this part is fairly crucial, no Subaru engine puts out quite that much in stock form, so it will need some modifications, albeit minor, and a good tune is pivotal in making the power and making it reliable).

 

Yes, there are several "FWD" conversion kits for Subaru 5- and 6-speed transmissions. Several different styles in how they block off the back of the transmission. Some require cutting the center diff housing in half, and just have a round plug where the diff would go, this is a cleaner, smaller solution. But in order to simplify converting back to "AWD", I think you'd prefer one with a bolt-on plate that deletes the last output housing, and leaves the center diff housing in place. Depending on access to the transmission itself, this could be done pretty quickly (transmission does not need to be removed to replace the center diff).

 

There are "RWD" conversion parts, that is basically just a solid chunk of steel with the appropriate splines to engage the transmission output, and the front and rear differential inputs. Or just get a spare center diff, and weld it solid...

 

 

Strength-wise, at 300hp, I don't think you have too much to worry about. In AWD or FWD mode, even a 5-speed should be able to hold up to it as long as you're not abusing it. In RWD mode, the transfer gears (between the center diff and driveshaft slip yoke), are proven to be the weak link. But, since you're talking about having it drive a propellor, there wouldn't be shock loading or anything like that, and I'm betting you probably wouldn't be using full power, so it might be fine.

 

 

Axles will depend on exactly what transmission you use and, more importantly, what knuckles you use. But suffice it to say, you have lots of options, and most will involve some custom/hybrid parts. I know when I was looking at 914 projects, there was a source for adapter flanges that slid over the older male-splines of the front differential, and allowed the stock porsche CVs to bolt to them. This would give you enormous options, and most of them would have greater travel than the Subaru options. Generally speaking, rear axles will not work on the front differential outputs.

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