rear axle ratio - quick method to determine?
Thread Starter
Team Owner
Joined: Apr 2001
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From: S.W. Ohio. . . . . . NRA Life Member
rear axle ratio - quick method to determine?
I'm not so sure that the wifes 1973 has a factory rear axle ratio. Although the speedometer is within 2mph of my '02; I am not convinced the car has the original ratio.
Is there a quick method to determine this ratio (like there is on a C5) ?
Is there a quick method to determine this ratio (like there is on a C5) ?
Burning Brakes
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From: Monument Colorado
Re: rear axle ratio - quick method to determine? (Mike Mercury)
Best way I know is the direct method: jack up the rear, put marks on the driveshaft and wheel, and see how many turns of the driveshaft you get with one turn of the wheel.
Drifting
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Re: rear axle ratio - quick method to determine? (Mike Mercury)
Another way is use the calculator at this web site http://www.prestage.com/carmath/calc_gears.asp
You will need the following info RPM, mph, tire height
You will need the following info RPM, mph, tire height
Thread Starter
Team Owner
Joined: Apr 2001
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From: S.W. Ohio. . . . . . NRA Life Member
Re: rear axle ratio - quick method to determine? (Tominator)
Tominator, I've seen that one before. I know it works on automatics that have lock-up torque convertors; but how would you figure in TC slip on the older cars?
Drifting
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Re: rear axle ratio - quick method to determine? (Mike Mercury)
That is a good question, I did mine with a rebuilt tranny and nonstock stall convertor 1800 - 2200 Summit brand and it was on the money. My understanding is once your convertor gets to a certain rpm it's locked or close to it.
The reason high stall convertors cuase so much driving around town is they're slipping, like if you had a 3500 stall and were driving around town at 2000 rpm it would be slipping.
At higher speed you should be good to check the speed and RPM.
The reason high stall convertors cuase so much driving around town is they're slipping, like if you had a 3500 stall and were driving around town at 2000 rpm it would be slipping.
At higher speed you should be good to check the speed and RPM.
Drifting
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Re: rear axle ratio - quick method to determine? (Tominator)
Another site U can try is http://www.smokemup.com. With a 3.55 rear end, I am turnin' 3K rpm @ 70mph.......... :cheers:
Team Owner
Joined: Jul 1999
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From: Orange Park Florida
Re: rear axle ratio - quick method to determine? (Mike Mercury)
ANY converter will have a 3-400 rpm slippage in there at any speed, like say a 400, hop on and off the gas at say 80 mph....yeh, it slips....
you have NO way to verify your speed or rpm's to an absolute to effectively use any formula....so forget about that approach...
best thing is just carefully count the rotations as stated before...
GENE
you have NO way to verify your speed or rpm's to an absolute to effectively use any formula....so forget about that approach...
best thing is just carefully count the rotations as stated before...
GENE
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Drifting
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Re: rear axle ratio - quick method to determine? (mrvette)
The calculator method may not be perfect due to slipage, however it is good enough to determine your gears.
If you hold a constant speed say 55 and then run the number through one of the calculators and it comes out to 3.51 or a 3.59 rear gear. At this point you can deduct it's a 3.55 rear end. IMHO
If you hold a constant speed say 55 and then run the number through one of the calculators and it comes out to 3.51 or a 3.59 rear gear. At this point you can deduct it's a 3.55 rear end. IMHO
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Re: rear axle ratio - quick method to determine? (Tex71BB)
Best way I know is the direct method: jack up the rear, put marks on the driveshaft and wheel, and see how many turns of the driveshaft you get with one turn of the wheel.
Drifting
Joined: Nov 2000
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Re: rear axle ratio - quick method to determine? (Tominator)
The calculator method may not be perfect due to slipage, however it is good enough to determine your gears.
If you hold a constant speed say 55 and then run the number through one of the calculators and it comes out to 3.51 or a 3.59 rear gear. At this point you can deduct it's a 3.55 rear end. IMHO
If you hold a constant speed say 55 and then run the number through one of the calculators and it comes out to 3.51 or a 3.59 rear gear. At this point you can deduct it's a 3.55 rear end. IMHO
Pro
Joined: Jan 2002
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From: Ashley Michigan
Re: rear axle ratio - quick method to determine? (GrandSportC3)
Best way I know is the direct method: jack up the rear, put marks on the driveshaft and wheel, and see how many turns of the driveshaft you get with one turn of the wheel.
:iagree:
:iagree:
Team Owner
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From: Greenville, Indiana
Re: rear axle ratio - quick method to determine? (tnt76vette)
If you do not have posi-traction, jack up one wheel, turn one revolution and multipy the driveshaft revolutions by two=ratio.
If you do have posi-tracion, jack up both wheels. Make sure both rear wheels turn one revolution. The revolutions turned by the driveshaft will = ratio.
Mike :)
If you do have posi-tracion, jack up both wheels. Make sure both rear wheels turn one revolution. The revolutions turned by the driveshaft will = ratio.
Mike :)
