turbo 350 tranny help

farmboy · Posted: Wed Apr 02, 2008 8:59 am Post subject: turbo 350 tranny help

i have just put a rebuilt turbo 350 in my 83 el camino. i am having issuses with the speedo gear not reading accuratly i have tried many different gears is there a way to get the right gear. other then just hit or miss. i have a 19 tooth driven gear in the tranny now

Thanks jon

rbohm · Posted: Wed Apr 02, 2008 10:50 am Post subject:

yes in fact there is a math solution. here are the formulas you need;

tire revs per mile=20800/(tire section width*2*aspect ratio/25.4+wheel diameter.

this works like this using a 205/70-14 tire

20800/(205*2*.70/25.4+14 which simplifies down to

20800/25.3=822

the second formula works like this;

drive gear*rear gear ratio*revs per mile/1000=driven gear

this works like this

6*3.55*822/1000=18 driven teeth.
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farmboy · Posted: Wed Apr 02, 2008 1:53 pm Post subject:

thanks is alot better then just guessing at the gear

Mama Mayhem · Posted: Wed Apr 02, 2008 4:15 pm Post subject:

Even easier use this calculator link: TCI Speedo Gear Calculator
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rbohm · Posted: Wed Apr 02, 2008 7:34 pm Post subject:

2hndsmke · Posted: Wed Apr 16, 2008 9:42 pm Post subject:

I have already found the TCI website but they do not stock the driven gear I need. I need a 7 tooth drive gear. Do you know of any other sources that would stock the gear I need?

2hndsmke · Posted: Wed Apr 16, 2008 10:02 pm Post subject:

never mind I found a site for anyone who's interested it is www.transmissioncenter.net/speedometer_calibration_______va.htm. The reason why I'm changing gears is because I'm switching from a 2.42 to 3.73