Reverse Rotation Automatic Transaxle. Planetary gearset?

#1
I realize this forum is geared toward mid engine cars, and that you often discuss rear engine style transaxles being inverted for mid engine use. I want to use a transmission that would already be longitudinal mid engine friendly and use it in a rear engine applications (A VW Super Beetle).

My idea is to use an Audi V6 2.7 twin turbo (or possibly another Audi V6) with a FWD longitudinal Audi automatic transaxle. I will not pretend to understand all the ins and outs of automatic transmissions (but I did successfully rebuild a 700R4 once), but I believe they can generally be reversed by locking one of the drums/shells/carriers of the sun gears.

I am wondering if it might be possible to make a 4 speed auto box (or 5 or whatever) have 4 reverse gears and one forward, which when turned around for a rear engine application, would give 4 forward and one reverse.

I realize one major drawback would be loading the wrong side of the ring/pinion gears when under the greatest load, and this alone could be the ultimate deal breaker.

I was going to include some pictures, but my post count is too low.

Any ideas?
 
#4
I believe subarugears mainly makes a reverse rotation ring and pinion for $1500 for a subaru manual, is that correct? I don't want to spend that much money on that aspect of this build for a 74 Super Beetle. I can find a Porsche 914 transaxle for $250 (my understanding is that you can flip the r&p to the other side in this box). But then I would still need an engine adapter. In that case I would probably use a Subaru motor. My idea of the reverse rotation auto is to be able to use a cheap JY solution.
 

Howard Jones

Gold Supporter
#5
I would think a donor boxer power train would work well in a mid engine VW project. The old boxers are getting pretty cheap and you would have all the electrical system to go with it.
 

Ron R.

New Member
#6
Not sure if I totally understand what you're trying to do, but I suspect its something like what Factory Five does with their 818 Subaru-based kit. They use a FWD engine tranny combo in a mid-engine application. You might take a look.
 

Doug S.

Lifetime Premier Supporter
#7
Not sure if I totally understand what you're trying to do, but I suspect its something like what Factory Five does with their 818 Subaru-based kit. They use a FWD engine tranny combo in a mid-engine application. You might take a look.
I own a Honda Accord that is about used up, except for the powertrain, which is still quite powerful. I always wondered why nobody manufactured a platform that would use a transverse fwd powertrain in a small, lightweight (fiberglass) chassis/body...it just makes sense!!!!!

If that 818 uses a WRX powertrain, it'll be a killer!

I would think a donor boxer power train would work well in a mid engine VW project. The old boxers are getting pretty cheap and you would have all the electrical system to go with it.
I use to spend some time on the Porsche "Spyder" replica forum...there was a guy who took a 550Spyder chassis and fitted a WRX powertrain in it...even he said it was SCARY FAST!!!!

I could see a Honda V-TEK V-6 or (even better--lighter and more powerful) a "boxer" Subaru WRX powertrain installed behind the cabin of a 246 Dino "kit"...but I guess nobody else can...or does...maybe one of the old Kelmark/Magnum Dino replicas? It just seems like a great combo!

Cheers!

Doug
 

Jac Mac

Active Member
#9
Maybe I read this first post wrong

I realize this forum is geared toward mid engine cars, and that you often discuss rear engine style transaxles being inverted for mid engine use. I want to use a transmission that would already be longitudinal mid engine friendly and use it in a rear engine applications (A VW Super Beetle). From this I assume you wish to retain the engine behind the rear axle, or do you want the engine fitted in rear seat area with trans behind rear axle

My idea is to use an Audi V6 2.7 twin turbo (or possibly another Audi V6) with a FWD longitudinal Audi automatic transaxle. I will not pretend to understand all the ins and outs of automatic transmissions (but I did successfully rebuild a 700R4 once), but I believe they can generally be reversed by locking one of the drums/shells/carriers of the sun gears.

I am wondering if it might be possible to make a 4 speed auto box (or 5 or whatever) have 4 reverse gears and one forward, which when turned around for a rear engine application, would give 4 forward and one reverse.

I realize one major drawback would be loading the wrong side of the ring/pinion gears when under the greatest load, and this alone could be the ultimate deal breaker.Not only reversing hypoid loads but also swaps thrust loads on some or all internal geartrain which could place major thrust loads on circlips where they are not designed for them

I was going to include some pictures, but my post count is too low.

Any ideas?
Clarify that for us & it will keep your thread on track!
 
#10
Maybe I read this first post wrong



Clarify that for us & it will keep your thread on track!
Yes I want to keep the car rear engine, i.e., engine behind rear wheels.

I think if you hold the drum of a planetary gear set, the shaft will run one way, but if you hold the carrier stationary it will turn in the opposite way. And I think there are other ways that auto transmissions reverse their rotation internally to provide different gear ratios. I think a sprag clutch, for example, is another device that reverses rotation or is involved in reversing rotation.

1. I want to use an Audi North-South FWD Auto transmission

2. I want to keep it bolted to it's intended Audi engine

3. , I want to turn the whole thing around so the engine is pointing backward

4. I want to make some internal changes to the hydraulic circuitry (or whatever) of the transmission so that I will have 4 speeds going the right way.

Is that clear?


Yes, I agree, that if I reverse rotation some of the forces might be going the wrong way.
 

Jac Mac

Active Member
#11
Yes I want to keep the car rear engine, i.e., engine behind rear wheels.

I think if you hold the drum of a planetary gear set, the shaft will run one way, but if you hold the carrier stationary it will turn in the opposite way. And I think there are other ways that auto transmissions reverse their rotation internally to provide different gear ratios. I think a sprag clutch, for example, is another device that reverses rotation or is involved in reversing rotation.

1. I want to use an Audi North-South FWD Auto transmission

2. I want to keep it bolted to it's intended Audi engine

3. , I want to turn the whole thing around so the engine is pointing backward

4. I want to make some internal changes to the hydraulic circuitry (or whatever) of the transmission so that I will have 4 speeds going the right way.

Is that clear?


Yes, I agree, that if I reverse rotation some of the forces might be going the wrong way.
Absolutely clear! Will it work?, depends on how the Audi transaxle is arranged internally & since I don't have access to one I'm not going to tie my grey matter in knots figuring it out- one correction in your last sentence above- substitute the word 'will' for 'might'.

'Lots of Luck'. based on your mention of potential costs earlier in this thread I would strongly suggest an adapter plate etc for a Porsche or other transaxle that is already in the correct configuration would be the best option.
 
#13
Audi and Porsche use the same bellhousing bolt pattern so you should be able to use a Porsche automatic from a 911 type car and bolt it up to the Audi engine. Good luck figuring out the electronics to get the Porsche transmission to shift.
 
#14
I'd be willing to be dollars that you can't do what you want to do with the Audi ZF transmission. Use the Porsche unit and be done with it.
 
#15
You can't spin an automatic backwards and have it work. The pump rotation is directional. If you happen to overcome that hurdle the thrust surfaces will be on the non thrusting side of the gear stacks. One way clutches only work in one direction... the list is endless.
 
#16
Why not just use a 912 engine and gearbox? Everything is oriented the right way for your Super Beetle. You can get 200hp out of a 912 engine with webers and big valves and cam. Powerful and light weight.
 
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