[sperry]

Originally Posted by huck369

The speedo gear in the Impreza (depending on the year and model of Impreza) is set up for as small as 13" tires, you are now turning 16" tires which are probably 10% bigger than the 13's it was set up for.....so your speedo is off....there are aftermarket fixes for this, but they do cost....

My little Daily Driver is a Impreza L FWD 5-Speed, which came with 13" wheels, and I have a set of 16" rims on it, and my Speedo is off 10%.....so 50 on the speedo is 55, 80 on the speedo is 88, and so on...you can just adjust your driving to match it, or open up the tranny and install a different speedometer gear set, or get an aftermarket electronic fix for it...

Wheel size has nothing to do w/ the speedo being off. Usually when you got from 13" wheels to 16" wheels, you're also going from 70 series tires to 40 series tires, so the overall diameter is similar. If your speedo is off, it's because you're not running the right size tires on those 16" wheels to match the original expected tire diameter from the original tires.

Try this page to sort out what you should be running: http://www.wheelsmaster.com/rt_specs.jsp

As far as the OP's problem. It sounds like he's got the wrong speed sensor in the tranny. Since he's running the same tires before and after the tranny swap (I'm assuming) there shouldn't be a discrepency due to the 5MT.