low rear axle gears and loose converters can have an adverse effect on a chassis dyno outcome.
I saw a S/C Corvette on the dyno when I worked at a race shop. 406 small block with a glide. 6500 stall and 5.38 gears. Dyno'd 440 at the wheels. Went 8:50@163 at the track. Dyno's are tuning tools, nothing more.
