so ive tried to do a search on this but every thread i find either doesnt correspond to my setup or says "this topic has come up before, just do a search". so what im wanting to know is what i will need to do to correct my speedo on a 91 Firebird after swapping from a 2.73 to a 3.42 gear ratio with 215/40/R15 tires. just for future reference, is there some formula or something that you can use to figure this out?

 

jus did this one in my 91... you need to chage out the speedo gears in your tranny... i had my tranny rebuilt and i just did it then... but shouldn't be very hard to get to... i think its jus removing the tail shaft for the one then the other one is right next to it... your going to need a 17 tooth drive gear and a 43 driven gear... its might be about 1-2 mph off but thats as close as i can get for the gear ratio you want... the two gears are going to cost about $25

http://www.transmissioncenter.net/sp...odESxZxQ#700r4

they come in the mail and should be at your house in 2 days!