8-Speed Automatic

[Nyoka]

I know, I know, it's heresy but...

If the 4-speed auto that bolted up to the RAM truck V10 was installed in a Viper with a Gear Vendors under-drive (both properly modified as necessary), I suspect, geared properly, it could be a very mean combo.

For the record, I would not consider this for my '08 Coupe but I had a conversation with a Gen II GTS track rat who was considering a 6-speed sequential setup and I thought I'd mention the auto swap possibility. He was very intrigued.

I was about to begin some research on "fit" issues but thought I'd ask the pros if you thought it was feasible.

Thanks for your input.

 

[Torquemonster]

I know, I know, it's heresy but...

If the 4-speed auto that bolted up to the RAM truck V10 was installed in a Viper with a Gear Vendors under-drive (both properly modified as necessary), I suspect, geared properly, it could be a very mean combo.

For the record, I would not consider this for my '08 Coupe but I had a conversation with a Gen II GTS track rat who was considering a 6-speed sequential setup and I thought I'd mention the auto swap possibility. He was very intrigued.

I was about to begin some research on "fit" issues but thought I'd ask the pros if you thought it was feasible.

Thanks for your input.

with a torque curve like a Viper V10 I can't see an advantage. What would be the point?

An overdrive on top gear could be useful if you run a lower rear gear but that truck auto will **** more power and add a large amount of weight while the OD will add even more weight.

Maybe a prepped powerglide and gear vendors would be better? or better still a prepped German 5sp auto by itself

 

[Nyoka]

The point of an automatic (vs a manual) is superior shift speed.

The point of an underdrive is to keep the motor in its sweet spot, no matter the gear. Using the Tremec 6060's gear ratios as an example, a .78 underdrive (like GearVendor's) gives you a 2.07 second-stage first gear (not a 1.78 second). All other things being equal, and despite the formidable Gen IV torque output, this should translate to measurable out-performance accelerating vs. a 'regularly' geared car. Road course "options" for the driver also double, something I would enjoy, having tracked my car numerous times on two very different courses yet I've never seen 4th.

Obviously, one would have to plan the gear ratios carefully (auto or manual) but there's no question in my mind that the additional gears would give the car more punch; an automatic would also significantly reduce shift speed and, possibly, the incidence of driver error. The driving experience would, admittedly, be quite different with an auto but it might be worth the trade-off for Formula 1-type efficiency.

The sole reason for suggesting the truck auto as a starting point was to hope for a clean bolt-up to the V10, i.e. no mods to bell housing. (A non-MOPAR option, e.g. BMW, would be too much trouble.) The torque convertor and internal tranny components would have to be custom and as lightweight as possible.

For the record, were I to take this project seriously, I would certainly evaluate the pros and cons of starting with a 3-speed vs. a 4-speed (no Powerglides in my future).

I appreciate your input and hope others pitch in as I continue this feasibility study. If anyone has dimensions of the 4-speed truck automatic (weight, length, gear ratios, etc.) in question, that would save me some research time.

 

[Torquemonster]

Firstly - while shift speeds are quicker than a T56 manual - this is offset by the loss of power to the rear tires on lower power cars (eg. 500rwhp). This loss of power is expressed as heat.

The cooling required to keep an auto working throughout a real road race will require considerable thought and space.

Auto's have been successfully raced at club levels, but will never compete with a good driver on a quick shift manual box due to the power drop and lack of engine braking. A sequential box like a Holinger will shift just as quick as an auto with far less weight, heat and power drop - so will be quicker - and by quite a lot.

Drag racing is different - and when you start ramping power up like with turbos - then an auto becomes a great option because power shifting a manual with 1500rwhp is never going to hook whereas the progressive and smoothness of a well sorted auto will be better at getting power down and the extra power it soaks up is more than offset by this. The heat is more easily managed too than in road racing where power is applied over a long time generating heat soak.

Secondly: it will not fit without extensive body work. Adding a Gear Vendors will make for a very short driveshaft. For the time and money spent cutting up the car and making the 4 sp Ram box work you might as well just go buy a Holinger which will be vastly better for road racing.

The Holinger can be ordered sequential and has no peer/equal in the road racing world for the Viper. They will shift as fast as you can move, and can even be shifted without the clutch, though you might want to lift between shifts rather than power shift clutchless. Their ratio options will ensure you can use more than the first 3 gears too.

In summary - unless you want to road race with 4 digit power - an auto offers only one advantage i.e. its easier to drive.

The downsides are:

1 - heat (road racing big power would make heat soak almost impossible to prevent in an auto) so the risk of DNF is high to extreme (esp. if you have more than 1 race);
2 - fit;
3 - loss of lap time vs a sequential or even a T56 due to power loss, slip, weight, lack of engine braking;


even if you can keep it alive for a race, you will be rebuilding an auto after every race weekend - guaranteed. Auto's HATE excess heat. You may make it work for 4-5 hot laps on a club day but that is a LOT of trouble to go to for something that could not handle a real race IMHO.

Not saying it cannot be done, just saying the obstacles are going to cost you way more than you imagine to overcome.

 

[Torquemonster]

if you are still serious about this - talk to Paolo at CPE Turbos - he has put one in a GTS and can tell you all about the work involved.

It'd be fine for a turbo drag/streetcar, not for road racing in my view. Paolo and others may disagree.

 

[GR8_ASP]

Most of Torquemonsters comments relate to planetary automatic transmissions with a fluid torque converter.Do they apply to planetary automatics with a launch clutch (aka Mercedes 7 speed used in performance cars)? Or dual clutch automatics using parallel shaft gear technologies similar to traditional manuals? Way too many different types of automatic transmissions to lump them into one category.

Even torque converter variants change the mold as the transmissions they drive increase the ratio spread and provide lock-up capability throughout the driving range. using the torque converter for anything beyond initial torque multiplication at launch will be a thing of the past shortly. And with it goes the heat and losses associated with automatics.

 

[Torquemonster]

Most of Torquemonsters comments relate to planetary automatic transmissions with a fluid torque converter.Do they apply to planetary automatics with a launch clutch (aka Mercedes 7 speed used in performance cars)? Or dual clutch automatics using parallel shaft gear technologies similar to traditional manuals? Way too many different types of automatic transmissions to lump them into one category.

Even torque converter variants change the mold as the transmissions they drive increase the ratio spread and provide lock-up capability throughout the driving range. using the torque converter for anything beyond initial torque multiplication at launch will be a thing of the past shortly. And with it goes the heat and losses associated with automatics.

not quite

anything less than cog on cog transmission has a power and efficiency loss - period. All these hi tech autos do is make up for power loss by faster shifts, and the sacrifice is still - heat - if you doubt it look at the race cars - they are all still manual. An electric/paddle shifted clutch on a manual trans is another matter.

Zeroshift is the ultimate in transmission technology but is still not yet available - and that is cog on cog - but with instant shift and no synchro, thereby offering the full width of the cog for power engagement compared to synchro boxes that have half the cog taken up by synchro. Zeroshift is also smoother than any auto. Once in production everything else will look like a dinosaur.

 

[Nyoka]

I'm pleased others have considered this concept seriously and I recognize that some have actually made the transition (with mixed results, no doubt), so I won't dispute the very comprehensive, and compelling, arguments presented here.

Overall, I would agree that the anti-track rationale makes some sense with the current technology but the intended application was mostly street, with some track/strip (probably <10%).

I never intended to design an auto from scratch, which is where this very sophisticated engineering debate is obviously headed. I was merely trying to match a bell housing with a block first, then deal with the durability and performance issues, later.

Like other enthusiasts, though, I have been impressed with the new generation autos offered by Lexus and Mercedes and believe a similar setup for a Viper could compete with the traditional manual in all but the most severe applications.

If I ever get this concept off the ground, I'll be sure to post details. Thanks for you interest and input; it's been very helpful.

 

[Camfab]

I'm pretty certain that the overall length of an auto with the Gear Vendors unit attached would leave you with an extremely short driveshaft. Quite possibly a stubby race powerglide would work, but a powerglide only has two speeds.

 

[Canyon707]

I really like the thought of an automatic for drag racing. It would be interesting to see for sure. I am sure we will see something one of these days. Lots of racing maniacs trying nes ideas.

 

[Paul Hawker]

Best automatic/manual transmission I have ever driven was the dual clutched 7 speed in the Ferrari California.

As one gear is being released, the next gear is already engaged. This allows not only a quick shift, but absolutely no lag in torque to the rear wheels during shifting.

Have to believe this would result, not only in very quick lap times, but also the ability to change gears in the middle of a corner, without upsetting the suspension.

I did not really understand the concept till I drove the car, but I cannot believe I would have been able to put down the power anywhere as smoothly with a manual.

Around town you could simply switch it into auto, and tool around. Was also good in stop and go freeway traffic.

Only places in auto racing using manual transmissions is where they are required by the rules. (includes drag racing)