Stupid question but how Do differential gears work?
Thread Starter
Instructor
Joined: Apr 2004
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From: Manahawkin NJ
Stupid question but how Do differential gears work?
Is it the amount of rotations of the driveshaft for every turn in the tire? Or is it the amount of teeth in the larger gear (The one attached to the axel I believe) To the amount of teeth on the smaller gear (The one on the driveshaft)?
I just want to know what size gears are better for what as I have no idea what size gears are in my 81 and would like to change em. (they are stock, anyone know what stock gears they had?)
Thanks
I just want to know what size gears are better for what as I have no idea what size gears are in my 81 and would like to change em. (they are stock, anyone know what stock gears they had?)
Thanks
Racer
Joined: Jan 2005
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From: Napanee Ontario
2024 C3 of the Year Finalist- Modified
According to the corvette restoration guide the 81 came with 2.87:1 (positraction with automatic, code OJ) or 2.72:1 (positraction with four speed, code OK)
Race Director
Joined: Mar 2001
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From: Living in the Hartland
When you hear a gear ratio stated it means the number of times the drive shaft turns per 1 rotation of the rear wheel, ie if you have a 3.70 rear end the driveshaft turns 3.7 times per tire rotation. You can determine your gear ration by jacking the rear end of your vette off the ground and rotating the tire 1 rotation and counting the revolutions of the driveshaft, helps to mark the shaft. The higher the gear ration the more torq that is applied to the rear end thus making easier for the eng to turn the tires, but is also reduces the distance the car will move so you trade the ability to accelerate faster for less top speed and lower gas mileage. You will need to change the speedo gear in the trans to match your new gear ration if you replace them.
Le Mans Master
Joined: Apr 1999
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From: Raleigh North Carolina
The ring gear is the big one... attached to the wheels. When it turns one revolution, the wheel turns one.
The pinion gear is the small one... it drives the big one from the engine/driveshaft.
The ratio is the number of teeth of the ring gear (larger number) divided by the number of teeth on the pinion gear (smaller number).... so you'll always have a number greater than 1.
I think I said that right.
The pinion gear is the small one... it drives the big one from the engine/driveshaft.
The ratio is the number of teeth of the ring gear (larger number) divided by the number of teeth on the pinion gear (smaller number).... so you'll always have a number greater than 1.
I think I said that right.
Team Owner
Joined: Jun 2004
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From: Smile, it's just the internet.
"4.11" would actually be 4.11:1 or 4.11 revolutions of the driveshaft (not engine) to one revolution of the halfshaft. The higher the ratio, the faster the car accelerates, but the slower mph it will max out at in any given gear. 4.11 and higher rear end cars are generally not fun on the highway because of the high rpm (3000+ rpm) of the engine at those speeds. Lower ratios, like my 2.73, are meant for better economy on the highway or higher top speeds.
Race Director
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if you want to be picky, the ring gear is attached to the posi case, not the wheels. The wheels, connected to the stub axles via the halfshaft are connected to the vertical spider gears, these are interconnected w/ horiz. spider gears on a center shaft and this setup is connected to the case by a clutch pack.....the stubs slide into the splines of the vertical spider gears. The posi case, spider gears & clutch pack make up the positraction part.
Last edited by Twin_Turbo; Mar 9, 2005 at 03:27 PM.
Team Owner
Joined: Jun 2004
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From: Smile, it's just the internet.
BTW, the only stupid question is the one which was never asked.
I've always found this site's explanations useful:
http://auto.howstuffworks.com/differential.htm
I've always found this site's explanations useful:
http://auto.howstuffworks.com/differential.htm
Le Mans Master
Joined: Apr 1999
Posts: 6,134
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From: Raleigh North Carolina
Originally Posted by Twin_Turbo
if you want to be picky, the ring gear is attached to the posi case, not the wheels. The wheels, connected to the stub axles via the halfshaft are connected to the vertical spider gears, these are interconnected w/ horiz. spider gears on a center shaft and this setup is connected to the case by a clutch pack.....the stubs slide into the splines of the vertical spider gears. The posi case, spider gears & clutch pack make up the positraction part.
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Team Owner
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From: Orange Park Florida
TT, I know you know how to explain how the open differential works....
spyder gears, side gears...etc.....
have at it....
for that matter how the application under torque of the posi clutches works....
I"d really love to hear a decent esplaination of that....it's a SUPER challenge to put that action down in written words....
you camd damn close up above....
jGENE
spyder gears, side gears...etc.....
have at it....
for that matter how the application under torque of the posi clutches works....
I"d really love to hear a decent esplaination of that....it's a SUPER challenge to put that action down in written words....
you camd damn close up above....
jGENE
Race Director
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Someone wrote it down not long ago,.... I think it was in the posi tuning topic, that was the best writeup I've seen on it...you're right, it is damn hard to put into words, maybe with a pic or an animation it could be done.
Melting Slicks
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From: Sodertalje/Sweden
Team Owner
Joined: Jun 2004
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From: Smile, it's just the internet.
Edit: oops. looks like BB wow beat me to it...
Open diff animations (flash movies)
Going straight
http://static.howstuffworks.com/flash/differential.swf
Turning
http://static.howstuffworks.com/flash/differential2.swf
Open diff animations (flash movies)
Going straight
http://static.howstuffworks.com/flash/differential.swf
Turning
http://static.howstuffworks.com/flash/differential2.swf
Drifting
Joined: May 2004
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From: Flanders NJ
Thread Starter
Instructor
Joined: Apr 2004
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From: Manahawkin NJ
You would think the less turns the driveshaft makes per wheel rotation the faster the acceleration?
Wouldnt the engine be putting out less power for the same amount of movement thus more power = more movement?
How does the bigger gear apply more acceleration?
Wouldnt the engine be putting out less power for the same amount of movement thus more power = more movement?
How does the bigger gear apply more acceleration?
Team Owner
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From: Smile, it's just the internet.
Engine power output doesn't change; just the way it's used.
It's a matter of leverage. Ever need to grab a bigger (longer) wrench to remove a stubborn fastener? Higher gears are the same as a longer wrench. They allow the engine to apply more force to the tires, but they have to turn slower as a result.
It's a matter of leverage. Ever need to grab a bigger (longer) wrench to remove a stubborn fastener? Higher gears are the same as a longer wrench. They allow the engine to apply more force to the tires, but they have to turn slower as a result.
Team Owner
Joined: Jul 1999
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From: Orange Park Florida
Originally Posted by CGGorman
Engine power output doesn't change; just the way it's used.
It's a matter of leverage. Ever need to grab a bigger (longer) wrench to remove a stubborn fastener? Higher gears are the same as a longer wrench. They allow the engine to apply more force to the tires, but they have to turn slower as a result.
It's a matter of leverage. Ever need to grab a bigger (longer) wrench to remove a stubborn fastener? Higher gears are the same as a longer wrench. They allow the engine to apply more force to the tires, but they have to turn slower as a result.
The above quite obviously true, but as a young kid with only a single speed Schwin bike, I had NO CLUE as the the affect of gears upon much of anyting.......today's kids got THAT comparo made into the seat of their pants....
GENE