My speedometer is off. Its acurate to 40mph but then gradually gets more and more off as It goes.......55mph is 63mph on my speedometer. 65mph is more like 78mph on my speedo. So Im actually going slower than what the car thinks. So when Im at the race track my car shuts off at roughly 95 to 100 mph...........An obvious pain in the ***. Now I had 373s put in so I know thats why but I dont know exactly what to get and how much it will cost. Also my speedo makes this awful clicking noise when I go.

 

Can't help ya, but thought I'd be nice and bump your post.

 

Your odometer is also off so miles are getting racked up a little faster then they should. You have 3 options, 1 - live with it, besines the speedo and odometer being off it doesn't hurt anything. 2 - you can try one of the speedo calibration boxes
I could not get the one I got to work. 3- your can either drop the tranny or tear up your floor board to replace the drive and driven gear in the tranny.

 

And sometimes yu can get away with just changing trhe driven (plastic) gear.

 

that plastic gear is a pita to get off and back on. i tore my hand upa bit, that thing had pretty sharp edges. if i were gonnas do it again id take it somewhere and let them do it. but thats me