I just swapped out the 110 speedo for a 145 speedo in my '90 Iroc but the new speedo isn't working. It's not totally dead, it'll read 10-15 mph when I'm actually going around 40 or so. Everything else seems to work fine, tach. seems pretty good, other gauges work, lights light up.

What could cause only the speedo not to work properly? Do I need any other parts to make this swap function properly? How should I go about trying to make this work?

Thanks.

Brian

 

Did you change you speedo gears in the transmission? If not I think you need to. You could get a reprogrammer. I think in plugs inline with the speedo cable. Just replacing the speedo gauge doesn't work.

 

Is that right? I can't see that there would be two sets of tranny gears for each rearend gear ratio, 1 for the 110 speedo and 1 for the 145.

 

Any other thoughts on this? Is freeman right?