Gear Ratios

Blackened · 12-13-05, 10:30 PM

Ok I don't quite understand Gear Ratios, is it the higher the better like 4.11 is better than 3.08?

67HEAVEN · 12-13-05, 10:41 PM

Quote:

Originally Posted by Blackened

Ok I don't quite understand Gear Ratios, is it the higher the better like 4.11 is better than 3.08?

Depends what you want. High numbers mean quicker acceleration at the expense of top speed. Lower numbers are the reverse......higher top end........slower acceleration.

Blackened · 12-13-05, 11:12 PM

Thanks, that explains everything really. Do the different gear ratios really mean that big of a difference though, say like a 3.55 and a 4.56 in acceleration?

Dave65 · 12-14-05, 05:23 AM

Quote:

Originally Posted by Blackened

Thanks, that explains everything really. Do the different gear ratios really mean that big of a difference though, say like a 3.55 and a 4.56 in acceleration?

It is a direct relationship. 4.56 divided by 3.55 is 1.28 so you get about 28% more force (torque) transmitted to the rear wheels, which results in more acceleration.

28% is also about the difference in gear ratio for 1st to 2nd and 2nd to third for a muncie 4 speed, so the difference is about the same as starting in 2nd gear rather than 1st gear.

Dave

firstgear · 12-14-05, 07:45 AM

Have a friend that has a rather stock looking 30 Ford Model A with a nice Chevy small block and tunnel ram....except for the wheels and the wheelie bars on back...you would never know....it has 5.86 gears in it....and shifts at 10,000rpm!

IH2LOSE · 12-14-05, 11:48 AM

Did they answer your questions?

Are you thinking of doing a gear ratio change.

When i was a kid and was looking for an inexspencive performance upgrade A gear change allways did the trick

Blackened · 12-15-05, 04:16 PM

Questions answered, not looking to change anything because I dont have a vette yet.

Just curiuous about the difference between them and what they do, thats all.

Sky65 · 12-15-05, 07:45 PM

This may help.
http://www.angelfire.com/fl/procrastination/rear.html

midyearroadster427 · 12-16-05, 09:34 AM

Quote:

Originally Posted by firstgear

Have a friend that has a rather stock looking 30 Ford Model A with a nice Chevy small block and tunnel ram....except for the wheels and the wheelie bars on back...you would never know....it has 5.86 gears in it....and shifts at 10,000rpm!

I dont think so.............not on a street driven car ......if he tells you he shifts at 10,000 rpm...he needs a new tach..

MarkM · 12-16-05, 10:00 AM

Blackened,

Thanks for the question - answers were a big help for me too. One more question for the experts, though.

I hear the gear ration mentioned as: " I have 4:11s in it", or "I have a 3:55 rear end" Does that refer to the ratio in first gear, total of all gears, or something else?

MarkM

67HEAVEN · 12-16-05, 10:13 AM

Quote:

Originally Posted by MarkM

Blackened,

Thanks for the question - answers were a big help for me too. One more question for the experts, though.

I hear the gear ration mentioned as: " I have 4:11s in it", or "I have a 3:55 rear end" Does that refer to the ratio in first gear, total of all gears, or something else?

MarkM

Mark,

That refers to the ratio of the rear end gear set. Things are further refined (and complicated) by the ratios of each gear in your transmission.

For example, if you have a none-overdrive transmission, then top gear is a 1:1 ratio......so the overall effect with a 3.55:1 rear end is just that....3.55:1.

However, if you have an overdrive transmission (let's say a 5-speed that has a .87 5th-gear), then your overall effect in top gear would be 3.55 x .87 = 3.08:1 overall.

MarkM · 12-16-05, 11:16 AM

Thanks. That helps. So, does the 3.55 in our example refer to a measure of first gear?

jreeves · 12-16-05, 12:27 PM

Quote:

Originally Posted by MarkM

Thanks. That helps. So, does the 3.55 in our example refer to a measure of first gear?

no, high gear

allcoupedup · 12-16-05, 01:56 PM

Switching from a low (3.08) to a high ratio rear (4.11) end is a major difference. You will feel like you are driving a completely different car.

I swapped transmissions from M21 (2.2:1 first gear) to M20 (2.56:1) first gear and the difference was night and day.

Brian

67HEAVEN · 12-16-05, 02:14 PM

Quote:

Originally Posted by allcoupedup

Switching from a low (3.08) to a high ratio rear (4.11) end is a major difference. You will feel like you are driving a completely different car.

I swapped transmissions from M21 (2.2:1 first gear) to M20 (2.56:1) first gear and the difference was night and day.

Brian

For those who may be new to this stuff, Brian is so right. What may not be evident to those unfamiliar with these things is that he is talking about two very different things in the above quote.

Although both items have everything to do with the overall final drive ratio, changes in gearing can be made in either the rear end....the transmission....or in both.

Brian's reference to the transmission swap from M-21 (close ratio) to M-20 (wide ratio) is an example of how the results can change by a simple change in transmission gearing. In that example, however, both 4-speed transmissions end up at a 1:1 ratio in 4th gear. They just get there in a different fashion, and were intended to be utilized by high horsepower engines (in the case of the M-21), or lower horsepower engines (in the case of the M-20). Also, these transmissions work best when matched to certain rear end gear numbers.

It can get much more complex than that, but you get the idea. Gearing can be a very important factor in improving the performance of a specific car, and more than anything, the choice in gearing is dependent on the intended use of the car. Gearing for a drag racer will be very much different from gearing for a road race vehicle.