What is your effective gear ratio?
Mar 16, 2005 | 10:52 PM
#41
14 Second Truck Club
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Joined: Oct 2004
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From: Chicago, Il
Originally Posted by Chevmann99
So at what point do you have too low a gear? I am at 3600 rpm at 75 mph in 3rd. So a 3.6 effective ratio, and Turn 2600 @ 75 in OD. I am running 35's w/ 4.88's. I regeared to get back to the factory 4.10/stock tire ratio and get my towing power back. I am also a member of the single digit MPG club 
(9.7 average since new, 36K now)
(9.7 average since new, 36K now)Back in the day transmissions had first gear in the 2-1 range, or 2.5-1 at best. Now, a 700r4/4l60 has a 3.06, so it will need less gear to get out of the hole the same as a muncie. Back then they ran 5.13 to get them going with their rock crusher transmissions with 2.20 first gear, that would be a 11.3 overall first gear. To get that in a 700r4 you would only need about a 3.73..
Also, for drag racing there are too many variables to determine gear ratio- like what speed you will pull through the traps and at what rpm. Some cars may do 100 mph at 5000 rpm at their best, others may do 120 at 5000. More power, more tire, more gear.
It may apply to a single car to make a single change, but their is no magic number. If you know what gears you actually have and know what you want to do, what difference does it make? How often do you drive in 1-1? If you want more gear you just decide how much on a car-by-car basis.
Im not really bashing, but their is no magic number for every car. There are soo many variables that effect gear selection- transmisison ratios, tire sizes, engine power and rpm, vehicle weight, intended use, current gear ratio..........
The only good formula to tell you where you are or where you will be is-
mph x gear ratio
----------------- x 336 = rpm
tire diameter
If you have any of the 3, you can get the fourth. If you want to pull 120 mph in the 1/4 with your 28" tall tire, with a 6000 rpm redline you would need a 4.16 gear, or 4.10.
Mar 16, 2005 | 11:13 PM
#42
Originally Posted by mzoomora
That is the main reason that this formula realy means nothing.
Back in the day transmissions had first gear in the 2-1 range, or 2.5-1 at best. Now, a 700r4/4l60 has a 3.06, so it will need less gear to get out of the hole the same as a muncie. Back then they ran 5.13 to get them going with their rock crusher transmissions with 2.20 first gear, that would be a 11.3 overall first gear. To get that in a 700r4 you would only need about a 3.73..
Also, for drag racing there are too many variables to determine gear ratio- like what speed you will pull through the traps and at what rpm. Some cars may do 100 mph at 5000 rpm at their best, others may do 120 at 5000. More power, more tire, more gear.
It may apply to a single car to make a single change, but their is no magic number. If you know what gears you actually have and know what you want to do, what difference does it make? How often do you drive in 1-1? If you want more gear you just decide how much on a car-by-car basis.
Im not really bashing, but their is no magic number for every car. There are soo many variables that effect gear selection- transmisison ratios, tire sizes, engine power and rpm, vehicle weight, intended use, current gear ratio..........
The only good formula to tell you where you are or where you will be is-
mph x gear ratio
----------------- x 336 = rpm
tire diameter
If you have any of the 3, you can get the fourth. If you want to pull 120 mph in the 1/4 with your 28" tall tire, with a 6000 rpm redline you would need a 4.16 gear, or 4.10.
Back in the day transmissions had first gear in the 2-1 range, or 2.5-1 at best. Now, a 700r4/4l60 has a 3.06, so it will need less gear to get out of the hole the same as a muncie. Back then they ran 5.13 to get them going with their rock crusher transmissions with 2.20 first gear, that would be a 11.3 overall first gear. To get that in a 700r4 you would only need about a 3.73..
Also, for drag racing there are too many variables to determine gear ratio- like what speed you will pull through the traps and at what rpm. Some cars may do 100 mph at 5000 rpm at their best, others may do 120 at 5000. More power, more tire, more gear.
It may apply to a single car to make a single change, but their is no magic number. If you know what gears you actually have and know what you want to do, what difference does it make? How often do you drive in 1-1? If you want more gear you just decide how much on a car-by-car basis.
Im not really bashing, but their is no magic number for every car. There are soo many variables that effect gear selection- transmisison ratios, tire sizes, engine power and rpm, vehicle weight, intended use, current gear ratio..........
The only good formula to tell you where you are or where you will be is-
mph x gear ratio
----------------- x 336 = rpm
tire diameter
If you have any of the 3, you can get the fourth. If you want to pull 120 mph in the 1/4 with your 28" tall tire, with a 6000 rpm redline you would need a 4.16 gear, or 4.10.
I agree with most of what you said and said so myself.
one thing effective gear ratio talk was good for was/is the convo which lead to a nice discussion of gears, powerbands, tire diameters, etc.
fun stuff if you ask me
Mar 17, 2005 | 12:39 AM
#43
There is no single answer... that is true. But if you do the test as we've described then you know where you are. And from there you can make adjustments as you see fit. No more mystery gears 
Mar 18, 2005 | 06:24 AM
#45
13 Second Truck Club
Joined: May 2004
Posts: 774
Likes: 0
From: East Texas
I checked my truck yesterday and it showed 3000 rpm at 75 mph, so that gives the VHOs on stock 20's a 3.00 ratio. Interesting. I'll have to check my 26" tall 16s and see how much difference they make.
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