Hello my name is John R, I purchased a 2018 Chevy Tahoe RST . Now I thought this truck was supposedly getting 420hp . I have a question for the community and anyone who can help me. Is that 420 at the wheel or at the crank?? I have seen Dynos that read 358 with 401 torque. How can this be if it is suppose to be 420 at wheel. Wouldn't that be false advertisement ??

Measured at the flywheel, more correctly flex-plate. There are parasitic hp losses through the automatic transmission, transfer case if so equipped, and differential. The automatic transmission being the biggest culprit. If you think it'* confusing now, back in 1971 they went from measuring what was called SAE hp to net hp, which took into account the hp loss from all of the accessories,power steering, alternator, mechanical fan, and a/c plus a typical exhaust rather than open headers. In some cases the hp drop was rather dramatic approaching 100 hp from the previously advertised SAE standards.

What garagerog said ^^^^^^^

. . . plus: What altitude are you testing at?