Jason-Middle Tennessee
Enthusiast
Why would you want to change over to a automatic? I've just always wondered this.
Hennessey Transmission Upgrade
- Thread starter Jason-Middle Tennessee
- Start date
pauls
Enthusiast
I think he means an automatically shifted stick shift. Like the Ferrari paddle.
Reason? Faster quicker shifts mean time, especially in Drag Racing. The rail shifter in the T56 is sloooow, and hard to make consistent fast shifts.
If we could even get a strong conventional automatic to fit a Viper without cutting it would shave 2 or 3 tenth of a quarter mile time.
Reason? Faster quicker shifts mean time, especially in Drag Racing. The rail shifter in the T56 is sloooow, and hard to make consistent fast shifts.
If we could even get a strong conventional automatic to fit a Viper without cutting it would shave 2 or 3 tenth of a quarter mile time.
Jason-Middle Tennessee
Enthusiast
Are you referring to the Automatic Stick Shift like in the 300M or just a plain Automatic?
Some of the Viper-auto transmission conversions have been for owners that have specific physical needs. A few years ago Viper magazine did a feature story on one such case in Japan.
Tom Welch
Enthusiast
I recently read about a company in Canada that has 2 vipers testing automatic transmissions. I wish i could remember the company name(maybe in the archives)
For drag racing the automatic transmission is far more consistant with regards to elapsed time. The drawback is it requires more horsepower to operate as it uses fluid pressure to transfer power and change gears. If you road race you will not like it as much as the current transmission.
I have considered a automatic transmission upgrade for the viper and have an excellent source for testing. The problems are that frame and interior console modifications will need to be accomplished, along with minor changes in the drivetrain and clutch pedal removal. How many viper owners would really want to go through all of the above?
I do feel though that an automatic transmission in conjunction with a solid axle style(dana 60 series) rear end, and a 3:55 to 4:10 gear ratio, would easily drop viper e.t's by at least 1/2 second. The mph of a quarter mile run is directly proportional to engine horsepower. Take a typical viper at 120 mph trap speed that is making 450 hp at 3500 lbs. and compare his 12.00 time to that of a typical drag car or even street car with an automatic trans and standard rear suspension and you get low 11's or high 10's from the same 120 mph generated by the other car.
I know it will work, i just don't think it will sell.
tom
"If we had some Ham, we could have some Ham and Eggs, IF we had some Eggs"
For drag racing the automatic transmission is far more consistant with regards to elapsed time. The drawback is it requires more horsepower to operate as it uses fluid pressure to transfer power and change gears. If you road race you will not like it as much as the current transmission.
I have considered a automatic transmission upgrade for the viper and have an excellent source for testing. The problems are that frame and interior console modifications will need to be accomplished, along with minor changes in the drivetrain and clutch pedal removal. How many viper owners would really want to go through all of the above?
I do feel though that an automatic transmission in conjunction with a solid axle style(dana 60 series) rear end, and a 3:55 to 4:10 gear ratio, would easily drop viper e.t's by at least 1/2 second. The mph of a quarter mile run is directly proportional to engine horsepower. Take a typical viper at 120 mph trap speed that is making 450 hp at 3500 lbs. and compare his 12.00 time to that of a typical drag car or even street car with an automatic trans and standard rear suspension and you get low 11's or high 10's from the same 120 mph generated by the other car.
I know it will work, i just don't think it will sell.
tom
"If we had some Ham, we could have some Ham and Eggs, IF we had some Eggs"
Mamba man steve
Enthusiast
I am not an expert on the actual et. difference but on a dyno a stick trans loses about 11-13% that can be checked on dyno. I had a blown BBC engine dyno'd after I built it. The loss at rwp was 27% give or take with a race turbo 400. The shop that I work with tells me a stick will always beat a auto.
Doug Supercharged Vipers
Enthusiast
[/B][/QUOTE]I am currently building and installing an automatic for my Supercharged GTS and will keep you updated on the progression.
Actually, the reasons you may opt for an automatic instead of a manual transmission is quite clear when you explore the facts.
If your a drag racer you may opt for the automatic for several reasons.
The automatic will allow much better ET's and durability far more than that of the Borg Warner Tremec, especially in higher horsepower applications. The Tremec is a strong transmission but has it's limitations compared to a Powerglide or Turbo 400. The automatic in conjunction with a transbrake (a solenoid lock to hold the transmission while holding the gas pedal to the floor) allows you to bring up the rpm's to smack the torque converter and launch the car.
A torque converter connects the engine to the automatic transmission, much like a clutch connects an engine to a manual transmission. Torque converters allow the engine rpm to enter the bottom range of the power curve and provide the optimum launch of the vehicle.
Most torque converters today will multiply torque by a ratio of at least 2 to 1. For example, if your motor is making 250 lbs.-ft. of torque and your converter is multiplying it by a factor of two, then the transmission will see 500 lbs.-ft. of torque.
Automatic transmissions are not as fuel efficient as manual transmissions and automakers must meet government-mandated corporate average fuel economy targets. So I doubt very seriously you'll see a Viper with an automatic from the factory in the near future, But the idea of an optional automatic transmission would be inspirational when you think of the durability and lower ET's for our snakes!
Best,
Doug Levin
Actually, the reasons you may opt for an automatic instead of a manual transmission is quite clear when you explore the facts.
If your a drag racer you may opt for the automatic for several reasons.
The automatic will allow much better ET's and durability far more than that of the Borg Warner Tremec, especially in higher horsepower applications. The Tremec is a strong transmission but has it's limitations compared to a Powerglide or Turbo 400. The automatic in conjunction with a transbrake (a solenoid lock to hold the transmission while holding the gas pedal to the floor) allows you to bring up the rpm's to smack the torque converter and launch the car.
A torque converter connects the engine to the automatic transmission, much like a clutch connects an engine to a manual transmission. Torque converters allow the engine rpm to enter the bottom range of the power curve and provide the optimum launch of the vehicle.
Most torque converters today will multiply torque by a ratio of at least 2 to 1. For example, if your motor is making 250 lbs.-ft. of torque and your converter is multiplying it by a factor of two, then the transmission will see 500 lbs.-ft. of torque.
Automatic transmissions are not as fuel efficient as manual transmissions and automakers must meet government-mandated corporate average fuel economy targets. So I doubt very seriously you'll see a Viper with an automatic from the factory in the near future, But the idea of an optional automatic transmission would be inspirational when you think of the durability and lower ET's for our snakes!
Best,
Doug Levin
Doug Supercharged Vipers
Enthusiast
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by steve(2001BlueRT)waiting:
I am not an expert on the actual et. difference but on a dyno a stick trans loses about 11-13% that can be checked on dyno. I had a blown BBC engine dyno'd after I built it. The loss at rwp was 27% give or take with a race turbo 400. The shop that I work with tells me a stick will always beat a auto.
<HR></BLOCKQUOTE>Steve,
I doubt the loss of horsepower on the dyno was due to your automatic directly.
I would surmise it may have been your torque converter. Your converter may have been slipping too much to provide a proper reading for the dyno. Remember, the converter is relative to many factors including weight of the vehicle. Just sitting on a dyno may not always allow the converter to hold the torque, your stall speed could have been to high, or just THE WRONG CONVERTER.
The term we use in racing is "too lose of a converter" or if you were to encounter too much wheel spin on the track during launch, "too tight of a converter."
Other factors that would implicate losses on the dyno can be..... Prop shaft (drive shaft) weight/length, heavier/bigger axles, gear ratios, temperatures etc...
Regards,
Doug Levin
I am not an expert on the actual et. difference but on a dyno a stick trans loses about 11-13% that can be checked on dyno. I had a blown BBC engine dyno'd after I built it. The loss at rwp was 27% give or take with a race turbo 400. The shop that I work with tells me a stick will always beat a auto.
<HR></BLOCKQUOTE>Steve,
I doubt the loss of horsepower on the dyno was due to your automatic directly.
I would surmise it may have been your torque converter. Your converter may have been slipping too much to provide a proper reading for the dyno. Remember, the converter is relative to many factors including weight of the vehicle. Just sitting on a dyno may not always allow the converter to hold the torque, your stall speed could have been to high, or just THE WRONG CONVERTER.
The term we use in racing is "too lose of a converter" or if you were to encounter too much wheel spin on the track during launch, "too tight of a converter."
Other factors that would implicate losses on the dyno can be..... Prop shaft (drive shaft) weight/length, heavier/bigger axles, gear ratios, temperatures etc...
Regards,
Doug Levin
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Mamba man steve
Enthusiast
Doug I should have made myself more clear. the stick we talk about which is the complete drive line. The automatic has that nasty converter and YOU ARE CORRECT.
Hey I have to learn to do that neat copy the other guy stuff.
I think the picture above this thread says a lot. My 40 Ford has the 400, trans brake, stall converter. I even put in an air shifter, and computer.
Hey I have to learn to do that neat copy the other guy stuff.
I think the picture above this thread says a lot. My 40 Ford has the 400, trans brake, stall converter. I even put in an air shifter, and computer.
Tom and Vipers
Enthusiast
Two comments:
1) I think THE automatic to use would be the 4L80 which is the GM TH400 with Lockup Converter and OD. I believe it is rated to 700 ft-lbs.
2) Don't condemn the T-56 for shifting poorly - the 12.2" clutch in the Viper is an abomination. The absolute maximum diameter for a single disk clutch is 11" if you wish to shift the transmission - and this is still undesireable!
For $73K you should get a high-tech double or triple disk clutch. You would have unlimited torque capacity and the rotational mass of 1/2 the 12". (Even those crazy turbo inport guys use triple disk clutches!)
The stock clutch is designed more like a truck than a race car. (Even the lowly dirt track racer uses dual disk clutches and GM even had one as an option in the original Z-28 and that clutch was a big hit with supercharged dragsters because it could handle 1400 HP right out of the box!)
I think the 12.2" clutch should be the topic of complaint - not the T-56.
Tom
1) I think THE automatic to use would be the 4L80 which is the GM TH400 with Lockup Converter and OD. I believe it is rated to 700 ft-lbs.
2) Don't condemn the T-56 for shifting poorly - the 12.2" clutch in the Viper is an abomination. The absolute maximum diameter for a single disk clutch is 11" if you wish to shift the transmission - and this is still undesireable!
For $73K you should get a high-tech double or triple disk clutch. You would have unlimited torque capacity and the rotational mass of 1/2 the 12". (Even those crazy turbo inport guys use triple disk clutches!)
The stock clutch is designed more like a truck than a race car. (Even the lowly dirt track racer uses dual disk clutches and GM even had one as an option in the original Z-28 and that clutch was a big hit with supercharged dragsters because it could handle 1400 HP right out of the box!)
I think the 12.2" clutch should be the topic of complaint - not the T-56.
Tom
Jay Herbert
Enthusiast
I know that East Coast Performance has done (fixed) one automatic (this is the one pictured above), Woodhouse has one in his shop and is fixing it as well. Both started somewehere else, failed and had to be fixed as the original shop did not take responsibility.
SVSi offers a six speed sequential racing transmission. I think an SVS customer posted here a while back and was loving it. It is an all out race piece though.
SVSi offers a six speed sequential racing transmission. I think an SVS customer posted here a while back and was loving it. It is an all out race piece though.
Tom and Vipers
Enthusiast
I didn't know about the 4L80 being a hog, however, could it possibly be the 400 w/non lockup converter?
I do agree about the **** factor of GM trans - especially when the Torqueflite, in my opinion, was the finest auto ever made. Of course I'm completed ignorant to the ones you described - I am very glad to hear that it is still around in various reincarnations.
I don't know, but I still believe manuals are faster than automatics. However, the manual MUST be powershifted and the driver must be highly skilled.
Still suffering from Viper euphoria - I bot my first one, an 00 GTS new!!!! Previously, the most I everspent for a car was $8K! Paid cash - better one monsterously obscene act rather than 60 of them once a month.
Remember Shiney Side Up
Tom
I do agree about the **** factor of GM trans - especially when the Torqueflite, in my opinion, was the finest auto ever made. Of course I'm completed ignorant to the ones you described - I am very glad to hear that it is still around in various reincarnations.
I don't know, but I still believe manuals are faster than automatics. However, the manual MUST be powershifted and the driver must be highly skilled.
Still suffering from Viper euphoria - I bot my first one, an 00 GTS new!!!! Previously, the most I everspent for a car was $8K! Paid cash - better one monsterously obscene act rather than 60 of them once a month.
Remember Shiney Side Up
Tom
Mike H
Enthusiast
Hennessey did do a automatic setup for a NJ VCA member...as he iis physically handicapped...the transmission did not survive very long, in fact it was completely redone by Chris Barone here in NJ....at his shop....the car runs very well now....hope this helps...
Tom and Vipers
Enthusiast
neonwannabee ....
From your response, it sounded like you were not offended by my kind-hearted ribbing!
You crazy import guys are quite amazing. Your technology level leaves all others in the dust.
Regarding the multi-disk, I read a feature on a car in Turbo and High Tech Performance and this guy was running something like a 3 disk 6" clutch ... or something like that. Sounded like someone made a clutch out of an automatic!!!!
As far as doing it the hard way. I am INTIMATELY aware of doing it the hard way. Because, my cross to bear was a 63 Paxton Supercharged Studebaker Super Lark (factory Paxton.)
This car was the "first Z28" because it was a complete package including suspension, instruments, and distinctive badges not to mention a Paxton supercharged 289 V8.
Back in 1974, I had not money, was going to college, and any speed mod to my car was fabricated by myself. The only aftermarket purchase I made for the car was a Chet Herbert cam for $50. However, I probably had 200 hours in the heads with OS Pontiac valves.
The car ran about 104-106 thru the stock mufflers on street tires. And one summer, I beat every single car that came to the local hangout - Winky's.
I don't think I would have to tell you the expressions I have seen on other driver's faces when I would beat their 396 with their girl friend sitting next to them on the bench seat!
My days of glory came to an end when I decided to try a Chevy diaphragm clutch and broke 2 axles, 1 driveshaft, and side gear from the Dana 44 posi. ....and then I restored the car and that was the final nail in the coffin.
However, I have gone from the ultimate sleeper to a Viper! This is like going from 0% to 100% in observables. The Stude was INVISIBLE to police while the Viper can be seen thru solid walls!
I've actually considered buying a turbo Supra a couple of times, but the car seemed just too heavy. If I had to buy an import it would probably be the 4wd Eagle.
___________________
Always keep the shiny side up!
Tom
From your response, it sounded like you were not offended by my kind-hearted ribbing!
You crazy import guys are quite amazing. Your technology level leaves all others in the dust.
Regarding the multi-disk, I read a feature on a car in Turbo and High Tech Performance and this guy was running something like a 3 disk 6" clutch ... or something like that. Sounded like someone made a clutch out of an automatic!!!!
As far as doing it the hard way. I am INTIMATELY aware of doing it the hard way. Because, my cross to bear was a 63 Paxton Supercharged Studebaker Super Lark (factory Paxton.)
This car was the "first Z28" because it was a complete package including suspension, instruments, and distinctive badges not to mention a Paxton supercharged 289 V8.
Back in 1974, I had not money, was going to college, and any speed mod to my car was fabricated by myself. The only aftermarket purchase I made for the car was a Chet Herbert cam for $50. However, I probably had 200 hours in the heads with OS Pontiac valves.
The car ran about 104-106 thru the stock mufflers on street tires. And one summer, I beat every single car that came to the local hangout - Winky's.
I don't think I would have to tell you the expressions I have seen on other driver's faces when I would beat their 396 with their girl friend sitting next to them on the bench seat!
My days of glory came to an end when I decided to try a Chevy diaphragm clutch and broke 2 axles, 1 driveshaft, and side gear from the Dana 44 posi. ....and then I restored the car and that was the final nail in the coffin.
However, I have gone from the ultimate sleeper to a Viper! This is like going from 0% to 100% in observables. The Stude was INVISIBLE to police while the Viper can be seen thru solid walls!
I've actually considered buying a turbo Supra a couple of times, but the car seemed just too heavy. If I had to buy an import it would probably be the 4wd Eagle.
___________________
Always keep the shiny side up!
Tom
...a matter of fact, Gary Dan and his automatic are featured in Viper Magazine that will be at your door in a few weeks.
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