What's my gear ratio??? - Team Camaro Tech
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post #1 of 11 (permalink) Old Feb 7th, 01, 07:24 PM Thread Starter
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Alright at 2500RPM I'm going 65mph in third gear in a TH350 tranny which I believe is 1:1 in third. My tires are 25inches diameter which is I think 78inch circumference.

I'd like to get more top end power but I don't want to spend alot either. What's the best way without losing too much off the line since I'm running a stock motor.
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post #2 of 11 (permalink) Old Feb 7th, 01, 08:37 PM
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A good bet would be 3.08's

Steve R.
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post #3 of 11 (permalink) Old Feb 7th, 01, 09:15 PM Thread Starter
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Got any idea how to figure it out? I tried the tech section but it didn't say. Is there anyway to find out without takin off the cover?
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post #4 of 11 (permalink) Old Feb 8th, 01, 04:00 AM
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Steve is right. Here is a webpage that can calculate the height and what gear you have and want. Bet you have 3.08's.

383 Speed-O-Motive stroker kit with Speed Demon 750, RPM intake,Proform HEI dist.MSD6a box,World Products Sportsman II heads, ported and polished with 2.02/1.60 valves,64cc,TRW forged pistons with 10.7:1 compression, Comp Xtreme 284 cam,Crane pushrods, Comp Cam 1.6 full roller rockers,ATI damper, 40 series Flowmasters, 4.11 gears with TH350 and 3000 stall.Powertrax NoSlip Locker
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post #5 of 11 (permalink) Old Feb 8th, 01, 07:42 AM
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If in doubt still, take the time and remove the rear cover and look for stampings on the ring and pinion gear if GM they should show the date and the number of teeth per gear. Divid low number by high number and your going to be close if not right on... Just another avenue.......
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post #6 of 11 (permalink) Old Feb 8th, 01, 09:58 AM
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I figured it out. Assuming that your toque converter has no slip (which is impossible unless you have a lockup converter) and your tach is right, you are running 3.08 gears. If I knew how many RPM the driveshaft was turning, I could give you a more definite answer. After torque convert slip is factored in and quite possibly tachometer error, you could be running 2.73 gears. Right off hand, I don't know of another gear ratio that is between 2.73 and 3.08.
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post #7 of 11 (permalink) Old Feb 8th, 01, 10:36 AM Thread Starter
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It's a stock converter. I woulda thought I was running a higher gear(3.73-3.50) since it basically revs out so quick.

Anyway on to my next question...how do I determine if I got a 8.5 or 8.2 10 bolt?

[This message has been edited by 67stock (edited 02-08-2001).]
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post #8 of 11 (permalink) Old Feb 8th, 01, 11:07 AM
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A easy way to find out ratio without taking cover off is to jack up car so rear
end is off the ground (DON'T FORGET THE JACKSTANDS) take the car out of gear using
a piece of chalk or crayon put a mark on
the driveshaft then one on the tire slowly spin the tire one turn count how many times the chalk mark on the drivshaft comes around
to its orig. position if you have 3:08 it will turn a hair over 3 times.
Want to know exactly gotta pull that cover
and go to counting. lol
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post #9 of 11 (permalink) Old Feb 8th, 01, 11:44 AM
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According to my calculations, you'll have a ratio of 2.80, 2.86, or 2.92 with a diameter of 24.5, 25.0, or 25.5 inches, respectively. All of the other variables can also make it go one way or the other.
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post #10 of 11 (permalink) Old Feb 8th, 01, 12:12 PM Thread Starter
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Well how do I tell if it's a 8.2 or 8.5 10 bolt?

Also check out my thread in suspension.
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post #11 of 11 (permalink) Old Feb 8th, 01, 12:30 PM
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67 stock

Go to www.novaresource.com and go under axle codes. The have a picture of the difference between 8.2 and 8.5's. as for the gear ratio. If it's an open rear, only jack 1 tire off the ground. Put the tranny in neutral. Mark the tire and shaft as stated before. Turn the tire exactly 2 revolutions and the number of turns on the driveshaft is the ratio. 2 and 3/4 turns= 2.73, 3 and a 'hair' turns= 3.08, 3 and 1/4 turns= 3.23 etc.

The 8.2's have an inverted 'V' on the cover. The 8.5's have a smooth cover. It's kind of hard to see in those pics..

[This message has been edited by mbrekke (edited 02-08-2001).]
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