Changed gears from 2.73s to 3.42 speedometer is off.

My question is. Is there a free program to do it with? I have the akm cable to hook up my pc to my car.


Thanks

Unfortunately, no. You need to buy Tunercat or LT1EDIT if you want to change your speedometer calibration yourself. Or you can buy a Hypertech. Or you can pay a custom tuner to do it. ;-)

For the OBD1 PCM interface I found a lot of the FREE stuff is pretty old, with non friendly GUI interfaces or they won't run on the newer Windows OS's. However you can download "C.A.T.S Tuner" free for 30 day trial period , and you will have to purchase the Definition File for $19.95 up front. I downloaded the Tuner trial software and purchased the $EE definition file to update my speedometer after my 2.73 to 3.42 '94 Z28 rear change. The more I used it, the more I liked it, so I purchased it after the trial. Also to see whats happening under the hood you can download "TTS DataScan" it will allow you 20 pulls for free (I like it, but the purchase cost is high).
By the way my 3.42 update gave me exactly the get up and go I was looking for without drastically effecting cruising capability. I was told to go to 3.73's' but now I'm glad I didn't for a street car. With 20%+ more RPM per MPH you will also find the 2>3 shift point settings in the normal and kickdown tables will hit the fuel cutoff rev limiter (5800 RPM) prior to the 2>3 shift at WOT. Also the TCC settings for the old RPM/MPH ratio will be 20% out of whack. If this is a project car you may want to invest in software for PCM tuning for the long run. Or make friends with a professional tuning source (previous post).