TH350/rear axle question

[smallengineguy]

I just put a GN rear in my 78 Regal. It has 3.42 gears in it. I also have a TH350 tranny in it. The speedo is now way off (reading too fast). Do i need a speedo drive gear in the trans with more or fewer teeth?

 

[Nordbert]

speedo info

Check out the speedometer gear reference section at TCI - Performance Transmissions and Torque Converters
under technical information.

 

[smallengineguy]

Great resource! Thanks!