This paper presents findings from a detailed investigation of in-train forces occurring in Aurizon’s coal haulage operations in the Goonyella region of Central Queensland. The work performed included a significant instrumented wagon based in-train force measurement program, combined with theoretical analysis achieved through computational simulation models. Aurizon’s coal wagons are operated in tandem pairs, each pair having a drawbar connection between the wagons and auto-coupler connections at the outermost ends. A significant change in recent times has been the introduction of short pack draft gears (polymer/elastomer springs without friction wedges) at the drawbar connections. Conventional draft gears are still used at auto-coupler connections. It was found from the detailed analysis of measured in-train forces that changes have occurred in the system behaviour of contemporary unit train consists as compared to those measured in earlier studies completed in the 1980’s and 1990’s. In particular, durations and occurrences of low frequency linear vibrations, have been significantly reduced in current consists. The paper provides a comparison of measured data and simulated data from older and more recent mathematical models to allow identification of the factors that have changed low frequency vibration behaviour. The paper provides a valuable update in the understanding of longitudinal dynamics and draft gear modelling.