Double ionization and subsequent ion-pair dissociation induced by low-energy collisions of Ar 8+ were studied for various methanol isotopomers to understand how the reactions of transient methanol dications correlate with the charge states of the scattered ions. Single-hit time-of-flight (TOF) spectra of recoil ions excluding multi-hit events show that long-lived molecular dications always correlate with Ar 7+ scattered ions, indicating that they are formed only by double-capture collisions that accompany transfer ionization. The double-hit TOF measurements of fragment ions show that the branching ratios of CH/OH cleaving largely depend on the charge states of scattered ions. The H/D substitution effect on the hydrogen migration indicates that a concerted motion of atoms is essential for this reaction pathway.