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Suby trans

kb_ara - November 26th, 2008 at 07:18 AM

I not sure if this has ever been asked BUT has anyone ever tried turning the crown wheel over in a subby transmission so it can be used in the back of a beetle thus removing the adaptor plate and weak gearbox from the equation? and also giving a strong 5spd and a good auto to play with.............

ttriebler - November 26th, 2008 at 07:41 AM

Yeah, it's been tried - refer to my build thread on the Samba "4WD conversion begins!"

http://www.thesamba.com/vw/forum/viewtopic.php?t=271863&sid=982997e0f670f...

In short, it can't be done. In the manual box, the differential is an "offset hypoid" design which means that if you flip the diff, the gears no longer mesh because they're at the wrong angle. Also, you need to relieve the case a bit to clear the crownwheel when it's on the other side of the case. The only way is to mae another crownwheel that has teeth at a different angle to the original, that now meshes with the pinion gear. Or...make reverse cut crown and pinion gears.

In the Auto, the pinion shaft is not in the centre of the gearbox, it's off to one side, and the crownwheel is centred in the case. So you cannot flip the diff in the auto. You can reverse the rotation of the pinion shaft be replacing it's 2 x drive gears with a double row chain - however, the crownwheel & pinion will be meshing on their 'weak' side, not designed to take the full load of the motor/trans. This 'may' result in significantly less strength in the diff.

The good news is I just shipped off my Subaru gearbox to a gear maker in India that is going to provide a solution. We will either design and cut a new pinion shaft/gear and crownwheel that are reversed or we will design and cut new crownwheel/pinion shaft/gear that works with a flipped diff and it's different offset angle. Once the gearbox gets to them, they will advise the best/cheapest course of action. At this stage it's around $4,000 USD to design and manufacture the reverse cut gears, which I'm getting done. Obviously other people will be able to purchase these once the initial design is done. But for approx $6k Aussie plus $2 to $3k for a good gearbox with PPG gears, you're looking at a very expensive box, not the cheap solution we had all hoped for.

pete wood - November 26th, 2008 at 10:08 AM

Quote:

Originally posted by kb_ara
...thus removing the adaptor plate and weak gearbox from the equation? and also giving a strong 5spd and a good auto to play with.............

the adaptor plate is completely secondary. lots of race cars use them and they are just not an issue. the real issue is that porsche are the only car manufacturer still mass producing rear engined cars...everyone else has seen the light and gone mid engined. I wonder when we will get with the program and do the same? :lol:

Without dissing what ttriebler is doing, a porsche box is probably a cheaper option in the long run. Our problem in Oz is that porsches are rare as hens teeth while subies are as common as political opinions.

BTW, I like the idea of are simple conversion to use a subaru five speed, but as has already been said, it's not simple or cheap. I thought about it some years back but the advise I got from a few mates was, even if you could do it, the market isn't big enough out here to support mass production numbers that would make it affordable. The US is a different proposition of course, but they have porsches and other aftermarket 5 speeds easily available and much cheaper than we can buy them over here. The other thing is, even if you use the trans in a purely 2wd configuration, the amount of surgery required on the chassis is enough to stop most people doing it. In short, a Berg5 would be easier.

The other thing is, for most VWs the factory trans is strong enough for a performance street car with only a few mods. People might like the idea of a 5 speed but they don't really need it. 5 speeds suit NA motors with fixed powercurves. Production cars only got 5 speeds to give them the overdrive top that VWs came stock with. So the "got a big turbo need a 5 speed" argument is just not applicable in a street car due to the extra torque the turbo provides. Race cars are a different story, they are money no object. Besides which, their isn't really anyone racing a big turbo VW outside of the drags...for which you only need a 4 speed. I'm rabbiting on here, but basically there are a handful of performance street VWs in Australia that could benefit from a 5 speed.

P.s. There is also the issue of fan speed, but I'll let you look up the Gene Berg website and read about that for yourself in his page on 5 speeds.

1303Steve - November 26th, 2008 at 10:14 AM

Hi

The other thing you could do is flip the whole transmission, but brings a whole host of other problems including oiling and the motor still needeing an adaptor plate as the transmission bolt pattern is not flippable like a VW one.

Flipping VW & Porsche transmissions is a common practice

Steve

VWCOOL - November 26th, 2008 at 10:19 AM

... just block the breather, dril another hole in top and add more oil!

ttriebler - November 26th, 2008 at 01:29 PM

Nice try on the 'just flip the Subaru transmission upside down' concept. Except that your differential will run without oil. Or add lots more oil so that the upside down diff gets some and watch it wreck everything else. The diff oil is shared with the gearbox oil so the gearbox will be overfilled. yechhhhhh and kapowwww.

If only Subaru had mad a front diff that wasn't 'hypoid offset' we could all be flipping them.
I have tried a few other diff centres in there as well including a Nissan GTR front diff centre, Subaru R160 diff centre but no go I'm afraid. You'll all just have to wait and see what India comes back with. If they can just grnd up a crownwheel gear with the teeth on a different angle to suit the pinion gear, the conversion will be cheap as chips. Aftermarket crownwheels are only a couple of hundred dollars at most.....but I don't like the chances.

Only reason I'm going forward with this expenditure is because I've had the idea of a 4WD Manx in my head for around 10 years and I'm just going to make it happen.

Hey Pete I'm not sure about the whole 'surgery on the chassis' if you used a Subie box in just 2WD. Those 2WD boxes are a lot shorter because they don't have a centre diff or an extension housing with gears to reverse the output for the tailshaft. My 4WD gearbox required me to cut through the torsion housing to fit but I'd say a 2WD one would fit without cutting through that. Maybe cut the std beetle tranny housing off but that would be about it I suspect.

pete wood - November 27th, 2008 at 08:49 PM

couldn't you just dry sump the subaru gearbox and then run it upside down? then you could pump the appropriate amount of oil on to the gears and diff and it could drain out of the bottom of the case below the diff and seperately below the gears.

On the other hand, if the R&P becomes cheap, I'd love to see an easy 2WD conversion. How plentiful are the 2WD boxes?

VWCOOL - November 27th, 2008 at 08:56 PM

I think Subaru has been exclusively 4WD internationally for around a decade...

mactaylor - November 28th, 2008 at 04:39 AM

plenty of 2wd boxes floating around but there is a company from NZ pilfering them by the dozens to put in a kitcar they are building dont know much about it other than they mid mount a wrx motor thru a built 2wd box.

1303Steve - November 28th, 2008 at 07:38 AM

Hi

I think flipping and using a special lubrication system like Peter said is doable, but I don't think the Subaru bellhousing bolt pattern is flippable, so maybe and adaptor would be needed.

You would end up with starter at bottom of the bellhousing, on the plus side is being able to use a stock Subaru flywheel and a host of performance clutches.

Steve

pete wood - November 28th, 2008 at 09:04 AM

for people wanting a cheap 5 speed for their dub motor, a conversion plate is par for the course anyway. I reckon that's where the real market is. the engine conversion market is much smaller and for people putting turbo engines in a porsche box would be stronger than the 2wd subaru box.

ttriebler - November 29th, 2008 at 01:30 PM

Plenty of 2wd Subie boxes around, and if you can only find a 4WD one it's easy to convert to 2wd - just take the centre diff out of it's housing. You will still have a long gearbox, but it will be 2wd. Haven't looked into the idea of getting rid of the entire centre diff & housing and bolting the rest of the tranny together, as far as I remember it's alldifferent studs and stuff. You'd prob have to make up some adaptor plate to bolt the nosecone onto the gearbox. Not total rocket science but a pain in the ass nonetheless.

Dry sumping the gearbox/diff and running it upside down is definately an option but not one I'm taking with my build. See how the ring/pinion thing turns out first.