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International Automotive Technicians Network
Re: Speedo and Tach fluctuating
Posted to HD/Fleet Forum on 3/21/2025

I can't pull up any service info on this for some reason, but my past experience with C5500 for inaccurate speedo is that the TCM for the Allison transmission is what communicates the VSS. If it has 4WD the transmission gets a signal from the TCCM of the 4HI o... Login to read more.