Automatic vs. Manual Transmission - Chevelle Tech
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Transmission & Driveline Transmissions and Differentials

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  #1  
Old Nov 19th, 09, 3:11 AM
658Chevy 658Chevy is offline
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Default Automatic vs. Manual Transmission

I know that:

- Auto transmissions suck up a lot of power.
- Due to "slippage" in an auto trans, not all the power gets to the wheels,
- All other things equal, cars with manual transmissions are usually rated with about 10% more horsepower.

What I don't understand is that if all this power is lost by using an auto trans, why don't all cars at the strip have manual transmissions? People cut-and-gut their cars and spend thousands to get that extra "tenth", but still keep their auto transmissions.

I've read about "torque multiplication", but am still foggy on the concept. What exactly is it, and does it compensate for the shortcomings of an auto trans? If not, why even use an auto?
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  #2  
Old Nov 19th, 09, 6:57 AM
BillyGman BillyGman is offline
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Default Re: Automatic vs. Manual Transmission

In many drag racing applications,automatics are more consistent, and consistency is the key to winning drag races in most race classes.
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Last edited by BillyGman; Nov 19th, 09 at 8:24 AM.
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  #3  
Old Nov 19th, 09, 7:09 AM
mr 4 speed mr 4 speed is offline
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Default Re: Automatic vs. Manual Transmission

....what Billy said


Quote:
Originally Posted by 658Chevy View Post
People cut-and-gut their cars and spend thousands to get that extra "tenth", but still keep their auto transmissions.
now that is an odd statement! Spend some time at a dragstrip and ask some questions
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  #4  
Old Nov 19th, 09, 7:35 AM
66 BRONZE 66 BRONZE is offline
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Default Re: Automatic vs. Manual Transmission

I think this guys down right scary with a 4spd.. This run was in the low tens but if you follow the other youtube post " scroll left at bottom of window, after you watch this one you can see this car has gone 9.43@ 139mph.. Now thats rowing gears!!!

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Old Nov 19th, 09, 7:36 AM
658Chevy 658Chevy is offline
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Default Re: Automatic vs. Manual Transmission

"now that is an odd statement! Spend some time at a dragstrip and ask some questions"

That's a good idea, but since I'm not at the track at the moment, I thought I'd use this fancy new Internet-web-surf thing and ask some questions here.
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Old Nov 19th, 09, 9:06 AM
mr 4 speed mr 4 speed is offline
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Default Re: Automatic vs. Manual Transmission

Quote:
Originally Posted by 658Chevy View Post
That's a good idea, but since I'm not at the track at the moment, I thought I'd use this fancy new Internet-web-surf thing and ask some questions here.


Have you ever been down a drag strip?
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  #7  
Old Nov 19th, 09, 11:23 AM
rak1 rak1 is offline
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Default Re: Automatic vs. Manual Transmission

That pretty much sums it up you cannot miss a shift or be late in an automatic.... Also in racing Automatic's they only lose about 7% hp so the consistency more than makes up for the slight loss in power, and don't be surprised if in the near future they get that number down to 5% or less.
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  #8  
Old Nov 19th, 09, 11:29 AM
Lilracr Lilracr is offline
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Default Re: Automatic vs. Manual Transmission

An older stick car is way harder to launch and get a good 60' without really low gearing, an automatic car has the converter to allow the motor to get to the desired rpm at launch and keep it there.
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Old Nov 19th, 09, 12:27 PM
cobaltchev67 cobaltchev67 is offline
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Default Re: Automatic vs. Manual Transmission

Automatic transmissions are generally less expensive and yes, more consistent than a comparably durable manual transmission. One thing the autos have over the manuals is they have a planetary gear design, meaning there's more surface area for the gears to contact each other, making them stronger. A manual transmission only has 3 gear teeth contacting each other at any given time, so breakage issues are more of a risk but that also helps with frictional losses....plus it doesn't have an internal pump.

Having said that, a manual transmission is more fun and more challenging IMO. Also, having the right clutch setup and shifter for drag racing is the key to being consistent(and not breaking parts) as well as knowing how to shift it. There's a reason Pro-Stock cars use manual transmissions....
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  #10  
Old Nov 19th, 09, 12:46 PM
Keith Tedford Keith Tedford is offline
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Default Re: Automatic vs. Manual Transmission

If you want reliability and consistancy at the track, you go automatic. People won't admit it, but very few know how drive a stick car any way. i prefer a stick car because it is fun on the street, takes a bit of skill to drive, and it keeps you humble. Just show off once and I can pretty well be sure that I will miss a shift and look like an idiot. To me, it is a real pleasure to watch a stick car go down the track when the driver knows how to shift. Lenco's don't really count as stick because they are basically an automatic with shift levers for each planetary gear set. What the guys above said about having a good shifter is so true. I had two cars back in the day with Muncie shifters. They were the quick road to engine and or transmission destruction if you beat on them. They were the first things thrown away. When I see one of these shifters in a car, I can be pretty sure that the owner isn't interested in pounding the gears. Not that you want to be pounding on these old car all the time. It is fun to do once in a while. Just the way I see it.....for what it's worth.
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  #11  
Old Nov 19th, 09, 10:15 PM
kboorman kboorman is offline
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Default Re: Automatic vs. Manual Transmission

I believe the biggest reasons are that automatics, for the same money, are stronger, more reliable and are easier on the rest of the drivetrain than a manual trans. They don't shock the drivetrain like sidestepping a clutch will and the only way around that with a manual is to have a certain amount of controlled slippage on launch. This requires the right type of clutch, which is more expensive and will require adjustment to dial in as well as maintenance. Using an automatic generally results in less parts breakage and more convenience.

That being said, I can't wait to do the auto > manual swap in my 66. I guess I'm just a glutton for punishment.
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Last edited by kboorman; Nov 19th, 09 at 10:34 PM.
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  #12  
Old Nov 19th, 09, 11:25 PM
rkd rkd is online now
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Default Re: Automatic vs. Manual Transmission

Having come full circle, and having a stick shift daily driver, and an automatic track toy, I don't see me doing near as well at the track with a stick shift.
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  #13  
Old Nov 19th, 09, 11:39 PM
658Chevy 658Chevy is offline
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Default Re: Automatic vs. Manual Transmission

I appreciate the replies. You've all answered my questions eloquently!
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  #14  
Old Nov 20th, 09, 1:37 AM
BillyGman BillyGman is offline
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Default Re: Automatic vs. Manual Transmission

Quote:
Originally Posted by cobaltchev67 View Post
There's a reason Pro-Stock cars use manual transmissions....
I thought that reason IS that it has to do with class rules. Atleast as far as I know, the rules in that race class dictate that manual transmissions be used, just as they also dictate that carburetors are used too, instead of fuel injection. I didn't think that all the drivers/owners prefer carberators over fuel injection, just as I don't think that they prefer manual transmissions over automatics. I believe that it's only due to the rules in that class that they use those things.

Just as Nascar vehicles MUST use mechanical fuel pumps rather than electric fuel pumps.These types of rules in those certain race classes were originally implemented in an effort to keep the playing field somewhat level. Another example would be the engine displacement limit of 500 cubic inches in top fuel dragsters.
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Last edited by BillyGman; Nov 20th, 09 at 3:26 AM.
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  #15  
Old Nov 20th, 09, 3:44 AM
aukai aukai is online now
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Default Re: Automatic vs. Manual Transmission

Variable slip converter.

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