Quantum mechanical calculations for the thermal rate constant of the combustion related reaction, CK4 + H --> CH3 + H-2 are reported. Benchmark full-dimensional results are given and compared to those derived from classical transition state theory as well as to some published reduced dimensionality results. The role played by some of the different degrees of freedom in the reactive process is investigated by comparing additional reduced dimensionality results to the exact ones. This proves valuable fur the development of possible strategies to study involved reactive processes.