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Sun Dec 30, 2007 8:39 pm

OK a few months of planning have gone by and things are moving forward. I am attempting to do what many others have tried before.....build a 4WD Manx.

Purchased 2 types of Subaru Auto transaxles as this would be the ideal gearbox for on-boost launches. As you can see from the pic, unfortunately they are just too long and too wide to fit within the chassis horns (or above or below).

So now I tried the Subaru Manual transaxle and this fits between the frame horns beautifully. It's still too long but looks like it can be made to fit.

See the front of the gearbox hits the chassis plate. Looks like I will need to cut this away to let the output yoke clear. Then I may still have to cut the torsion bar area away to get the front cover of the gearbox to clear as well. This would then be reinforced with a 'hoop' welded over the top of the whole assembly. And I guess I would have to run coil over shocks. Not such a big deal!! Or can the torsion bar splines be rewelded to be on the outside of the frame horns so I can retain torsion bar suspension?

For those of you wondering about me having 5 reverse gears and 1 forward gear....the age old problem of not being able to flip the Subaru diff!!!! I have found there's 2 things that need to be done to achieve this. (1) Some of the reinfocement ribs need to be ground down in 1 side of the casing to allow the crownwheel bolts to clear. This is easy enough with a dremel and carbide bit. This makes the ribs the same size as the ones on the other side so no big deal there.
(2) I am having a reverse cut driven gearbox shaft/pinion gear cut and matching reverse cut crownwheel made. I have two quotes, one from USA and one from India where they make tons of this stuff and Labour is cheaper.

Any intelligent comments and advise would be appreciated, especially from people who have modified this rear part of the chassis before and fitted coilovers etc.[/img]

Sun Dec 30, 2007 9:14 pm

Is this going to be just for street of street/offroad use, if you are going to run around a 31''-- 33'' tall tires you might want to think about a R&P around 5-1,
If you get this to work put me down for one, I have a 5 speed box waiting to go into my buggy along with a 2.5 turbo engine, get this to happen and you will become an overnight business with buggy- Baja- rail and Beetle guys all aroung the globe 8)

Sun Dec 30, 2007 9:17 pm

I have never done just what you are planing but the hoop idea would work IMO. with stock cars, hot rods and go karts the best way I`ve come up with doing something along those lines to to make your bracing hoop, weld it in and then cut out the area you need. This keeps everything in place and inline.
If there is any worry about strength after grinding down those ribs, what about building a strapping type over-case?
Sounds like you are not afraid of fabbing, so the first hurdle is done :D
There are lots of coil-over shock options and almost all would have different rate of springs you could use.
Another thought, what about fabbing a complete chassis?
Whatever route you way you go, I for one, would like to see the progress of your build. Someone always has to be the inovator of new ideas and makes it easier for the next person to do and maybe improve/evolve an idea. best of luck and keep us informed.

Rayth

Sun Dec 30, 2007 9:24 pm

Ken Trongo built a 4WD Meyers Manx (Classic Manx Serial #15). Its called Fourplay. He used a VW Syncro transaxle with a Chevy S-10 front differential. He built the frame from tubing. You can see a small picture of it on his Avatar on the RBC website. His website name was Bugzapr. He passed away in 06 but you could probably get more pics from his son if you asked on the RBC webpage.

http://bugzapr.e.yuku.com/t/bugzapr-Avatar.html

Mon Dec 31, 2007 3:55 pm

Thanks for the replies guys. This project is for the street only, in fact I want to drag race it. So the R & P will stay at the standard WRX of 4.11. Once the initial design of the shaft is done it shouldn't be too hard to manufacture different ratios if people need them.

Be aware that these R & P sets will run around $4000 US, that's what I have been quoted to date, not including the design costs. So it still makes for an expensive gearbox.

Great idea about welding in the hoop before cutting and keeping everything aligned. I will be doing that as soon as I get the transaxle back from the gear manufacturers, I have to send them the sample box.

I have thought many times about using syncro parts for this conversion but I have a fear that they will not be tough enough to do the job and new parts are difficult to come by. Hence the Subaru WRX project continues. This is getting an EJ20TT motor behind it so it needs to be strong.

Got plenty of work to do in the meantime so I think the next steps will be to get the front diff and axles/cv's in place.

Tue Jan 01, 2008 2:44 am

You can retain the torsion bars if you use the short swing axle torsion bars with the IRS trailing arms. this lets you put the inner torsion bar anchors in the frame horn with some extra bracing.

Tue Jan 01, 2008 5:52 am

I would consider cutting off the frame horns and fabbing new mounts from scratch along with using coil overs shocks that would be adjustable for the added weight of the Subi parts.
Here is a pick of a custom trans mount and with a few changes that could be a Subi gearbox in there :D

http://s241.photobucket.com/albums/ff42/Jogyver/?action=view&current=IMG_0905.jpg

I think trying to utilize the VW parts will just make the build that much more difficult.

Tue Jan 01, 2008 6:05 am

There is a manx here in Brisbane Australia that runs a type3 auto and has cut off the frame horns and made a new section wide enough for the auto to fit. Might be a better way to go.

Tue Jan 01, 2008 10:37 am

I like Rayth's idea with the hoop. If you make the hoop
out of 2X2 box instead of round, it would make it easier
to modify the body lip for a clean fit. Just a idea.

Wed Jan 02, 2008 3:46 pm

With a powerful engine hanging out the rear, the front end will lift, loose traction and just spin the front wheels. I didn't see what kind of traction control system you're going to use

If you mid-mounted the engine, it would be exactly where you want the weight for acceleration, braking and handling, without any of the direction of rotation issues or need for TCS. Without the extra weight of a second transaxle, a mid engine would outperform a rear engine 4wd version in every way (except maybe off-road). With the flat water cooled Subaru engine you could fully cover it with a fiberglass deck and have a large rear cargo area. You'd also have plenty of space to mount the radiator under cover in back where the engine would have gone.

Wed Jan 02, 2008 7:47 pm

Don't forget that I will have the added weight of the front differential, front driveshafts, front uprights and brakes, CV's to help keep the nose down. I would say this would add perhaps 80-100kg to the weight on the front of the vehicle and balance it up very nicely.

As for traction control, the Subaru has it's own inbuilt traction control in the manual gearbox setup, using equal length driveshafts. Any wheelslip automatically transfers power to the opposing wheel(s). So in theory if the front lifts off the ground, more power will go to the rear until the front drops down again.

Look what turned up yesterday......the EJ20TT - twin turbo Subaru!!

Wed Jan 02, 2008 8:28 pm

Original Manx wrote: Any wheelslip automatically transfers power to the opposing wheel(s). So in theory if the front lifts off the ground, more power will go to the rear until the front drops down again.

Seems to me that if the front tires are lifting and spinning that means the backs already have lots of traction and power (remember weight transfer when accelerating). Adding more power to the back will only cause the car to accelerate more and the center of gravity to transfer further back thus unloading the front even more.

Am I missing something?

Also I don't understand the need for the special ring and pinion gear sets you mentioned. How is that going to make the trans work for a rear engine layout? Can't you use the Subby ring and pinion set once you modify the case to allow for flipping the ring gear (crown wheel)?

Wed Jan 02, 2008 9:59 pm

John you may be right but I'm told these things wheelspin tremendously with this sort of power so there's a good chance the back will wheelspin rather than lift the front up. I dunno, it's all theory at this stage. Let's see what happens when the thing gets going. It probably also somewhat depends on how the power is delivered, it might be better if it's delivered higher up the rev range like this turbo motor so the buggy already has momentum.

To answer your ring and pinion question - once the gearbox case clearances are done and the diff centre is flipped, it then rotates in the correct way to give you 5 forward gears and 1 reverse gear. However, because the R & P are a Hypoid gear set (i.e. off-centre unlike 9 inch diffs) the teeth on the gears no longer mesh once the centre is flipped. Hence the need for new R & P with gears cut at a different angle.

I did up a bunch of pix and explanations when I got quotes from the gear companies so I have included them below, hopefully they illustrate the process for everyone. cheers.

Wed Jan 02, 2008 10:19 pm

Original Manx wrote: As for traction control, the Subaru has it's own inbuilt traction control in the manual gearbox setup, using equal length driveshafts. Any wheelslip automatically transfers power to the opposing wheel(s). So in theory if the front lifts off the ground, more power will go to the rear until the front drops down again.

I understand that Subaru continuous AWD manual transmissions "normally have a 50/50 front-to-back power split and they use a mechanical viscous center differential to to vary the power split when there is a loss of traction". But didn't you say you were using an automatic transmission?

I understand the other Subaru transmissions "use traction sensing computer input to electronically vary the front to rear power split via a hydraulic multi-plate transfer clutch". Sounds pretty complicated.

I suppose you could get a viscous differential from a manual transaxle system and adapt it to the automatic transaxle system, but I wonder why Subaru didn't offer that option.

http://www.cars101.com/subaru_terms.html#awd

Wed Jan 02, 2008 10:49 pm

BL# Manx - I can't get the automatic transmission to fit without cutting off the frame horns so am using a manual transmission and it's 4WD system. This has the centre diff built into the back of the transmission.

I finished opening up the chassis to make it all fit today and must say I'm fairly happy with how it turned out. First off I cut out the torsion bar housing and ground down the torsion tube till they're flush with the frame horns (clearanced the frame horn lips just a touch to get enough room)

Ground down the top and bottom sheetmetal to form a nice curve. The top sheetmetal is cut back to where the inspection hole was and the bottom sheetmetal is cut back to where the pan goes from curved to flat.

My plan is to get in there with the mig welder and weld up where the torsion tubes meet the sheetmetal as this has been weakened. I will then create a horseshoe shaped piece to weld back into this entire gap to re-strengthen it, with just a hole in it for the front of the gearbox (drive yoke) to poke through. Where I have removed the top and bottom sheetmetal, I figure I can create two new pieces like 'dimples' that I can weld back on and will clear the gearbox case top and bottom. This should give me back all the strength of the original chassis.

Here's how it fits, I have placed some 'cups' around the gearbox drive shafts to approximate the size of the CV's to ensure I have clearance on the frame horns.

I'm quite pleased with the fit. I made the pan level on the jackstands and looked at the gearbox angle, quite good, we should not have any problems with oil starvation. I could lower the back of it a touch by cutting out 'dimples' in the frame horns for the CV's to have more clearance like on Superbug horns but I'd rather leave the horns intact. It looks like I can weld the original Subaru gearbox mount across the bottom of the horns and have a nice sturdy rubber mounted gearbox!!

Wed Jan 02, 2008 11:20 pm

That looks like the easy bit.....what are the plans for the front end?

Thu Jan 03, 2008 12:36 am

Plans for the front end are to cut an access hole in the frame head and slip the Subaru R160 diff in there (upside down). This looks like it can quite easily be bolted into the frame head. Then it's a case of reinforcing where I've cut to make everything strong again.

I am going to use the Subaru front hubs on this project to replace the VW spindles. I plan to make a steel insert for the lower VW control arm that replaces the VW ball joint. The lower Subaru ball joint will bolt through this steel insert. I intend for the steel insert to be drilled off-centre so I can rotate it for caster adjustment.

For the upper part it's a little trickier - the Subaru has struts. So I need to make a bracket that bolts to the top of the Subaru hub and allows the VW ball joint from the VW top control arm to bolt through it. If I make it adjustable with some sort of thread I can also adjust for camber.

You would be amazed at how similar I've found all Subaru dimensions to VW dimensions......!!!!!

Thu Jan 03, 2008 12:47 am

I look forward to see how you go.

Fri Jan 04, 2008 10:17 pm

Okay, I understand the ring & pinion gear problem. That really sucks! If the center lines of the two gear were on the same plain, it would be a snap.

So if you can get these gear sets made you'll be in business. May even be a product worth selling if you can get a few made. Not sure what the market for that would be.

Fri Jan 04, 2008 10:44 pm

Wouldn't it be cheaper to just make the engine spin the opposite way? Seems like if you go the right computer and programmed it correctly the engine should be able to run in the opposite direction easily...

Just an idea.....