Cascade Crew

91camaro_rs · Posted: Fri Apr 09, 2010 9:25 pm Post subject: posi conversion

im pickin up a posi rear tomorrow,

how much will the speedo be off if the rear has 373 and the ones i have now are 323?

Twilightoptics · Posted: Fri Apr 09, 2010 9:32 pm Post subject:

tciauto.com

racing calculator

91camaro_rs · Posted: Sat Apr 10, 2010 7:24 am Post subject:

ok, so if the posi really is 3.73 then my speedo will be 8 mph slow... so how do i find out exactly what the gear ratio is? and what all do i need to make the speedo accurate?

91camaro_rs · Posted: Sat Apr 10, 2010 7:44 am Post subject:

anyone have a link to the chart that tells the number of teeth you need for each gear ratio? i remember seeing it once but i cant find it again Laughing

redlava · Posted: Sat Apr 10, 2010 8:22 am Post subject:

http://www.transmissioncenter.net/speedometer_calibration_______va.htm

If you see something on the website that is not in-stock, just call. They do not update there site often.

BTW you need a new housing to hold the new plastic gear, the stock one will not work.

91camaro_rs · Posted: Sat Apr 10, 2010 4:09 pm Post subject:

got the posi home and cleaned up the outiside of it and took the brakes and stuff off, everything was rusted together, and i figured out it has 3.08 gears...and my car has 3.23 now so i want to stick with the 3.23 and that way i dont need a new speedo gear, i can just swap tailhousings. cause i gonna just put the posi unit in the rear end i have now

Alphius · Posted: Sat Apr 10, 2010 8:04 pm Post subject:

91camaro_rs · Posted: Sat Apr 10, 2010 11:34 pm Post subject:

posi came out of a 87 iroc, 5 speed

so if i keep the 3.08's in there how many teeth is the speedo gear have that i will need to make sure the speedo is right?

91camaro_rs · Posted: Sat Apr 10, 2010 11:53 pm Post subject:

so i tried using the calculator and i rember the color of the gear on my transmission, its the greenish yellow one (19 tooth drive gear)

so in my car now i have a 19 tooth drive gear and according to the calculations with a 26.8 wheel (is that the right wheel height?) i have a 46 tooth driven gear, and it says with 3.08 gears and a 19 tooth drive gear i will need a 44 tooth driven gear to make the speedo correct...does that sound right?

Alphius · Posted: Sun Apr 11, 2010 11:09 am Post subject:

91camaro_rs · Posted: Sun Apr 11, 2010 1:02 pm Post subject:

wow that was dumb of me to think i was gonna use the V6 tailhousing lol

the gear on the V8 is red which is the 17 tooth gear,

using 25.6 inches for the tire height and 3.08 for the ratio i get a 41 tooth gear

bought the gear and the new housing