Grass Roots Motorsports Solution To Building A Corvette C5/C6 Midengined Transaxle

Calling all machinists and mechanics.

While researching a way to convert a Corvette C5/C6 drive train into a mid engined configuration I have found several great ideas which never went anywhere and that seem to only exist in pictures.

How would Grass Roots Motor Sports design and build a poor man's high horsepower transaxle? Something made out of plate steel from Send-Cut-Send. Maybe aluminum plate.

1) The Vector W8 with a transverse drive train and 3 speed auto.

2) Longitudinal drive train with heavy duty chains transferring the differential's output forward to CV axles near the flywheel.

3) Longitudinal drive train with heavy duty drive belts transferring the differential's output forward to CV axles near the flywheel. I once saw an advertisement in an old copy of Circle Track Magazine for such a thing but never heard of it again.

4) Longitudinal drive train with with what appears might be a transfer case or Toronado chain transferring the differential's output forward to CV axles near the flywheel. Ready for sale but the only thing that exists is a photo from a PRI show.

I want something like #4 but without all of the fancy and expensive housing. I somehow have to attach a chain drive sprocket to the Vett's differential splined out shaft and then connect a chain drive sprocket to the half shaft CV joint.

Can I assume that all of these transfer case and Toronado transmission chains are virtually all the same and thus could theoretically be made any length and width?

Vector W8

The DCT from the new C8's appear to be available for $6-8k. That's going to be cheaper/easier/more reliable than any of the above.

In reply to BA5 :

Ha, that sounds like a bargain considering my Ford Windstar's emergency out-of-town rebuilt transmission cost something like $4000.

What layout is acceptable? Does it have to go

engine - diff - trans

or is it OK to go

engine - trans - diff

?

In reply to AngryCorvair (Forum Supporter) :

Engine-Trans-Diff and then back up near the bell housing with a home brew chain belt drive for the CV axles. Just like that fancy Side Drive one except without the fancy aluminum housing.

So it sounds like you want to use the C5/C6 engine and transaxle in a mid-longitudinal setup but you don't want the extreme powertrain length that would result from running the axles directly out of the diff like this.

Is using the C5/C6 gearbox really necessary? If not there may be cheaper options such as a C8 DCT or an adapted Porsche or Audi gearbox, or possibly even a dedicated race transaxle if you can find a good deal on a used one.

If it is, then you're stuck with using some of these addon gearboxes to move the diff output forward again, an approach that I don't think is worth it...

If a transverse/lateral setup is an option, it could be possible to adapt a Toyota EA60 or U660E, these were used in the Evora and should stand up to the torque of an LS.

Boxster S 6-speed is the usual answer but how much HP is 'high'?

Those chain and belt drive systems all seem like complicated solutions to the problem of using the wrong transaxle. 

I'm thinking I need a 1000hp twin turbo LS for my World's Fastest Street car to be middle of the pack. When I started, the fastest cars in the world were 180mph and I designed it  front engine because I read somewhere that weight distribution and polar moment of inertia where important. I guess 35/65 weight distribution is just fine and 50/50 is more of a suggestion.

I just see a need for a cheap, strong IRS unit and if with just one little cheap fix the C5/C6 would be a great GRMS type solution.

It's got to be better than using a front wheel drive transfer case on an engine turned 180 degrees. Maybe not.

In reply to VolvoHeretic :

If you want to hold 1khp that makes the C8 DCT look like an even better option. Sounds like this is for a drag racing class? If so, would a dual-powertrain EV be legal? At that level of power the costs could be similar and the EV might have more potential to keep up in the future.

BA5 said:

The DCT from the new C8's appear to be available for $6-8k. That's going to be cheaper/easier/more reliable than any of the above.

Sure, but does it have cheap and easy independent control options available?

An 01E would probably live okay with no shock loads and a cooler to keep oil temps in check.

This may not be a Boxster 01E...  the five speed 01E from the five cylinder S6 is probably the strongest trans Audi ever made, they handle drag racing shock loads behind engines well over the power levels you are contemplating, with all wheel drive traction to prevent drivetrain-saving wheelspin.  And they have built in provisions for an external transmission cooler.

This was also used in the five cylinder S4, but the S6 had a wider 1st gear.  (Like, the case is slightly different to accommodate the physical width of the gear)  Probably irrelevant for your needs.

You'd need to convert it to "front" wheel drive, but this is relatively trivial compared to simply finding one, or doing the kinds of mechanical hackery that you are already contemplating.

To give an idea behind how Audi transmissions are, the weakest unit, the 01A, is good to about 600hp in a road racing environment as long as you don't hop curbs under power.

In reply to GameboyRMH :

This is for the World's Fastest Street Car class of highway terror. Also for people like Mugglesworth.

Evidently the 1970 500ci Caddy Eldorado put out 400-425 HP and Torque 550-575 lb-ft (gross). So, two chain belts, one for each axle and tire should easily handle 1100 lb-ft of torque.

I just need to learn about these chain belt drives. And bearings/spindles to hold and drive them.

All this talk of chains for a DIY/GRM solution has me thinking skip the Vette and go straight to Frazer-Nash...

In reply to Driven5 :

I keep getting ideas to take a transmission, machine off all of the gears, and install sprockets and motorcycle chain.

Transmission efficiency would skyrocket because chains are pretty much 99% efficient vs gears at 80-90%, and you could REALLY choose what ratios you had.  The chains would either explode quickly or last forever running in a constant oil bath.

Pete. (l33t FS) said:

In reply to Driven5 :

 

Transmission efficiency would skyrocket because chains are pretty much 99% efficient vs gears at 80-90%

Really? My experience is exercise machines-but one of the many arguments for belts was not having the many, many, many tiny friction laden links in a typical chain.

In reply to MrJoshua :

Bicycles have chains because it's the most efficient way to transfer power from one shaft to another.  People keep trying new things because OMG 1800s TECH but when you're a low powered machine that can tell the difference between tires at 100psi and 120psi from the added rolling resistance, every little bit is important.

In reply to Pete. (l33t FS) :

My curiosity was the efficiencies quoted for chains vs gears. I have a hard time believing the numbers. For bicycles it seems more convenience driven than efficiency. Chains are an easy way to connect a power source  to something of a variable size a variable distance away. A belt or gear requires a much more specific design that cant be adjusted for length by a guy with a chain breaker.

People have tried gear drives, just as people have tried belt drives, to try to eliminate the maintenance intensive chain.  It always ends up being a power suck.

The logistics are not insurmountable, as there are shaft and belt driven motorcycles.

It's easy to try in the real world, too.  Ride a bike with a gear reduction hub like an old Sturmey-Archer or one of the newer Shimano units.  They feel a lot more laborious to ride for the same gear inches until you get to the 1:1 ratio.

(I haven't seen "gear inches" used as a term for a very, very long time, so at the risk of mansplaining, the gear inches is what the effective gear ratio/tire diameter combo would equate to if you were riding a penny-farthing or other device that directly connected the crank to the drive wheel, with that diameter tire.  So a 27" tire with a 32 tooth front sprocket and a 16 tooth rear sprocket would be 54 gear inches - one rotation of the pedals would be the same traveling distance as one rotation of a 54" tire)

In reply to MrJoshua :

Not to derail the topic too far, but I worked in the bicycle industry for a long time, and was around when Gates was making a big push to try and gain market share for their belt drives. This was for single-speeds, or internally-geared hubs only. They had some claims, but when pushed for data/evidence/studies to back those claims, the best I saw was, "Well, if you look an off-road race bike with a worn, poorly-tensioned, dirty roller chain with zero lube running in a mud/grit bath, and compare it to a good belt with proper tension running in the same conditions, it can be argued that the belt *might* have an efficiency advantage, and if nothing else, it is quiet-running and doesn't wear the sprocket as quickly!" 

Our single-speed race team riders had some choice criticisms of the belts. My takeaway was that it is an interesting idea that probably has a place on bikes where quiet operating and low-maintenance for cleaning/lubrication are important, and that don't see lots of instant torque...like a short-trip urban commuter in an area with few hills. There's a reason that the roller chain reigns supreme for bicycle usage. When you've got more than human power on tap, absolute efficiency probably isn't as much of a concern. 😁

wonder what inspired this thread...   🤔

anyway, there is also the option of using a corvair transaxle in various orientations or a quick change diff in front of the transmission, anything is possible with enough fettling.

https://grassrootsmotorsports.com/forum/grm/adding-an-oil-pump-to-a-corvairkelmark-transaxle/162866/page1/

see this chaps solution, unfortunately it looks like the build stopped or he stopped posting - https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/mid-engine-v8-barchetta-build/173785/page1/

VolvoHeretic said:

In reply to GameboyRMH :

This is for the World's Fastest Street Car class of highway terror. Also for people like Mugglesworth.

I've seen you post this concept several times, and forgive me if you've already mentioned it but what is the reasoning for having the extra set of wheels at the front? Seems like it's adding a lot of complexity, weight and cost, and I'm not sure what the benefit is. Are you planning on running 2 separate steering racks to steer the two sets of front wheels? If so, how do you connect the steering shaft to both racks? It can be a bit challenging to dial out bump steer and get the correct ackerman one set of front wheels, let alone two. Are you planning on running 6 sets of brakes or do the extra 2 wheels not have brakes? If you are set on having 6 wheels for some reason, wouldn't it make more sense to have the extra wheels in the rear for added traction (assuming rear wheel drive)? I'm just trying to understand the justification for it.

There are actual transaxles available 

http://www.mendeolatransaxles.com/transaxles.html