Can these odometers be turned back, or do they have the protection built in where the numbers get all mis-aligned when you tamper. If so, how?

The reason I'm asking is that I'm swapping transmisisons in my 82 T/A for one with an electric signal, and I have this speedo available from my parts car. I'd like to set it to what the odo in the 82 is currently at.

Thanks in advance!


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82 T/A 305/TH350; soon to be 350/T-5

 

it can be done. you have to take the odometer apart. do not attempt to spin the numbers there are small plastic tabs that keep the numbers aligned that will break.

 

The digital clusters use an 8 pin DIP package 256 bit serial EEPROM (electrically erasable programmable read only memory) to store the odometer info, which is written to every time the ignition is switched off. The 8 pin chip is mounted in a socket, & has a plastic "carrier" clipped onto it. Unfortunately, the info in the EEPROM is encripted & if the proper check info is not retreived from the EEPROM by the processor on the cluster board, the display will show the text "error". I've viewed the data stored at various mileage increments, but have been unable to crack the encritpion algorithm - anyone from GM out there that has any idea of the method of encription?? However, if your present cluster is digital, you may swap the EEPROMs (pull the chip up, out of the socket) and the mileage will transfer with the EEPROM.

Tim

 

This isn't a digital dash, normal 85 mph cluster.

Any more directions/advice for tearing into the odometer? I'm pretty good at figuring out how things work, is it pretty simple?


Thanks guys