The Plastic Lizard

I need to flash the ECM of a 2002 Corvette C5 so that it will work in my 1984 C4 Vette.

the C5 corvettes had the speed sensor on the rear differential, but my speed sensor is on the tailshaft of the 4L60e.

From another source I know I need to change the following 3 commands. But what else do I need to change. Right now my ECM thinks the speed is a lot higher than it is and doesn't shift gears appropriately.


command .....................................Vette / Fbody

Ho101 vss pulses per km...............19279 / 65000
Ho102= vss pulses per revolution ..... 12.6836 / 40
Ho104= trans output shaft rev/ km ..... 519.98 / 1625.12

N20zuki

What program are you using to tune the ECM? You can just change the PPM value to what you need for the VSS signal to work properly.

The Plastic Lizard

I am not sure...I am sending the computer back to the guy who originally programmed it. I am assuming he will know all the right questions to ask, but then again...he was the one who programmed it this way, knowing it was going in a C4....not a C5.

I want to make sure that the transmission shifts properly and everything else is corrected.

ls1nova71

iTrader: (4)

Definitely just change the VSS info. If you flash it to an F body tune, you will loose your DBW.

Russ K

iTrader: (1)

And select no to Transaxle of FWD, then just change all the speedo tables to match a 1999-2002 F-Body A4. Next, input your tire size & gear ratio & hit the commit button.

Russ Kemp

The Plastic Lizard

Thanks everyone...

Russ,

I know my tire size, and when you say gear ratio...you mean the rear differential right? I have a Dana 36.

Rear axle ratio for stock 84 Dana 36 was 3.07



Everyone else...if I had done this before, "change to fbody" would make sense....but I don't want this guy screwing it up again, can you be very specific which parameters change? Is it just the three above?

Russ K

iTrader: (1)

Yes, gear ratio=rear differential.

Russ Kemp