y2k_ta

iTrader: (80)

I have a TH400 out of an '89 G20 Chevy van that had the 5.7L engine.

I've seen all the calculators online (messed with TCI's already). My tire height is 28" & the gear ratio is 3.42. I'd like to get a driven gear so my speedometer will be correct, but I have no idea what drive gear I have. The transmission is already in the car, so I was hoping for a "cheat sheet" somewhere that might list the drive gears used in a particular vehicle. Does one exist or do I need to crawl under the car?

Thanks for any help!

Scott

Yank

iTrader: (181)

go to your local GM dealer they have the tire size speedo ratio charts

chris718

The formula is the axle ratio(3.42) x the number of teeth on the drive gear(15 is common) divided by the tire diameter(28")x 20.2.So 3.42 x15 divided by 28x20.2 +# of tooth on the driven gear.

forcd ind

iTrader: (7)

i have a sheet somewhere, i'll see if i can dig it up-if you do a google search, i think theres a couple out there also

y2k_ta

iTrader: (80)

Thanks fellas!

forcd ind

iTrader: (7)

if you want to PM me your email, i can scan them and email it to you
seems it comes out to a value of 2.46, 15T trans gear, 37T speedo gear

y2k_ta

iTrader: (80)

Thanks! pm sent.