Danok72

I have a 94 Z28 with unfortunately a 2.73 rear end. I have opportunity to get a 3.42 out of a six speed car from the same year. What will I need to do to make this work ? I have heard the computer has to be flashed to recalibrate to the different gear. Is this difficult to do or have done ?

Injuneer

You have to tell the PCM what gears you are running so it can send the correct info to the speedometer and the odometer. Also needs correct speed info to control shifting, decel fuel cutoff and other computer controlled parameters.

You can send your PCM to a mail order tuner, find a used Hypertech Power Programmer cheap, or get PCM tuning software. Mail order is the easiest.

Danok72

Could I use the PCM out of the 3.42 geared car even though it is a manual ? I know of a parts car with a 3.23 that is an auto that I could swap the rear end and the PCM but I would rather go with the 3.42s if possible.

Injuneer

The program in the PCM has to match the trans type..... same PCM, different program. You need an auto trans program to run your 4L60E electronically controlled auto trans. With the PCM/program from a manual trans car your trans won't work. It gets even more complicated because the output pulse rate from the vehicle speed sensor on the auto trans is significantly different from pulse rate from the VSS on the manual trans.

You might be able to find a used Hypertech for about $50. It can adjust for rear axle ratio, tire diameter, rev limiter, speed limiter and shift points. You just need to be sure the original owner returned his PCM to stock or the Hypertech will not work on your car.