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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
post #1 of 19 (permalink) Old Nov 19th, 09, 3:11 AM Thread Starter
Senior Tech Team
 
Join Date: Apr 2006
Location: OR
Posts: 1,359
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?
658Chevy is offline  
Sponsored Links
Advertisement
 
post #2 of 19 (permalink) Old Nov 19th, 09, 6:57 AM
Lifetime Premium Member
 
Join Date: Oct 2005
Location: CT,USA
Posts: 12,212
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.

70 Chevelle SS clone (632 CI powered).

Last edited by BillyGman; Nov 19th, 09 at 8:24 AM.
BillyGman is offline  
post #3 of 19 (permalink) Old Nov 19th, 09, 7:09 AM
Lifetime Premium Member
 
Join Date: May 1999
Location: Under the hood of some musclecar
Posts: 25,225
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
mr 4 speed is offline  
post #4 of 19 (permalink) Old Nov 19th, 09, 7:35 AM
Senior Tech Team
Eric
 
Join Date: May 2007
Location: USA
Posts: 1,810
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!!!


1966 Chevelle 300 Deluxe Post, 327cu AFR180CC Street Eliminator, Voodoo, Harland Sharp 1.6 RR, Weiand Stealth Airstrike, 650cfm avs, MSD 4spd 355 posi

http://i183.photobucket.com/albums/x...2/P1010428.jpg
http://i183.photobucket.com/albums/x...2/P1010429.jpg
66 BRONZE is offline  
post #5 of 19 (permalink) Old Nov 19th, 09, 7:36 AM Thread Starter
Senior Tech Team
 
Join Date: Apr 2006
Location: OR
Posts: 1,359
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.
658Chevy is offline  
post #6 of 19 (permalink) Old Nov 19th, 09, 9:06 AM
Lifetime Premium Member
 
Join Date: May 1999
Location: Under the hood of some musclecar
Posts: 25,225
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?
mr 4 speed is offline  
post #7 of 19 (permalink) Old Nov 19th, 09, 11:23 AM
Senior Tech Team
Robert
 
Join Date: Jul 2006
Location: Reno.NV
Posts: 2,547
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.

'67 Elky Global West suspension kit with coil over QA1's, 435hp Edy Crate,700R4, Currie +9 3:75, Disc brakes front and rear, Dakota Digital gauge package, 12 Circuit Painless wiring kit, Ididit tilt Colum, etc.
2012 HD Tri-Glide in Vivid Black.
1967 XR7 Cougar S code 390.
2016 Charger R/T in Purple.
rak1 is offline  
post #8 of 19 (permalink) Old Nov 19th, 09, 11:29 AM
Senior Tech Team
Bobby
 
Join Date: Nov 2008
Location: Va.
Posts: 1,731
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.

-Bobby-
1965 SS 331 Muncie
Lilracr is offline  
post #9 of 19 (permalink) Old Nov 19th, 09, 12:27 PM
Lifetime Premium Member
Mike
 
Join Date: Jun 2007
Location: Puyallup, WA
Posts: 2,935
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....

1967 Chevelle Custom
SBC 383
Gear Vendors Overdrive
Jerico DR-4
S60, True Trac, 3.54 gears
http://s348.photobucket.com/albums/q...67%20Chevelle/
cobaltchev67 is offline  
post #10 of 19 (permalink) Old Nov 19th, 09, 12:46 PM
Lifetime Premium Member
Keith
 
Join Date: Sep 1998
Location: Ontario, Canada
Posts: 7,858
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.
Keith Tedford is offline  
post #11 of 19 (permalink) Old Nov 19th, 09, 10:15 PM
Senior Tech Team
Kirk
 
Join Date: Sep 2003
Location: Langhorne PA
Posts: 1,449
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.

Last edited by kboorman; Nov 19th, 09 at 10:34 PM.
kboorman is offline  
post #12 of 19 (permalink) Old Nov 19th, 09, 11:25 PM
rkd
Senior Tech Team
Ron
 
Join Date: Oct 2006
Location: Ocean Springs MS
Posts: 4,345
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.

66 Malibu Coupe, home rebuilt 350. Took me 39 years to get her!
rkd is offline  
post #13 of 19 (permalink) Old Nov 19th, 09, 11:39 PM Thread Starter
Senior Tech Team
 
Join Date: Apr 2006
Location: OR
Posts: 1,359
Re: Automatic vs. Manual Transmission

I appreciate the replies. You've all answered my questions eloquently!
658Chevy is offline  
post #14 of 19 (permalink) Old Nov 20th, 09, 1:37 AM
Lifetime Premium Member
 
Join Date: Oct 2005
Location: CT,USA
Posts: 12,212
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.

70 Chevelle SS clone (632 CI powered).

Last edited by BillyGman; Nov 20th, 09 at 3:26 AM.
BillyGman is offline  
post #15 of 19 (permalink) Old Nov 20th, 09, 3:44 AM
Lifetime Premium Member
Mike
 
Join Date: May 2006
Location: Kapaa Kauai Hawaii
Posts: 8,369
Re: Automatic vs. Manual Transmission

Variable slip converter.


YOU KNOW YOU HAVE THE POWER..... AND IF YOU USE THAT POWER BAD THINGS ARE GOING TO HAPPEN!!

Mike Lewis street 572
http://www.lewisracingengines.com/
Holley HP EFI
Marcella Manifolds
Heads by Darin Morgan
Cam by UDHarold
.456 X 1.8/1.7
Menscer Motorsports
http://menscerms.com/
R2C Filters
www.r2cperformance.com
Ultra Carbon
www.ultra-carbon.com/
GF-5R,
http://trzmotorsports.com/wp2/
TRZ FAB 9" 4.56 REM, Cryo Treated
4000 lb street car
My Showroom
aukai is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Chevelle Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address. Note, you will be sent a confirmation request to this address.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome