069 Posted July 15, 2009 Share Posted July 15, 2009 (edited) how to shift a 12 speed split,overdrive-1985 mack R613? also need manual Edited July 15, 2009 by AACC Quote Link to comment Share on other sites More sharing options...
Guest 45LMSWM Posted July 16, 2009 Share Posted July 16, 2009 Shift it just like a five speed, only you can split each gear from high to low. You can drive it all in high if you want, all in low and then split 5th into high for overdrive. More than one way to do it. I always used the mud stick as that was how my boss told me, but you don't have to unless your heavy or on bad ground. You can split the mud stick into high/low as well and you can also use it in reverse. Some 12s have a 2nd stick or "mud stick" and others have an air switch on the dash for the lo hole.Good thing about a 12 speed Mack, 6 speeds reverse!!!Regards,John Pearson Quote Link to comment Share on other sites More sharing options...
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