Gmerrill0516 Posted May 24, 2011 Share Posted May 24, 2011 Picking up my B-815SX shortly and am wondering why I see this set up referenced as having both 18 and 20 speeds. I see the plaque in the truck says to not use 5th in I believe low-split and direct. Why is this? Can you use it when empty or will it damage something? I'm wondering what ratios are in each box. See lots of guys on line shifting just the aux until they get to 1st direct then continuing with 2nd-4th to 18th. Is there a 20 speed version? Any and all information is appreciated. Would 5th direct be an overdrive technically?Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/19174-quadbox-question/ Share on other sites More sharing options...
mowerman Posted May 24, 2011 Share Posted May 24, 2011 the reason for that,is its the same gear ratio as the gear you were in..such as the ten speed duplex,generally you skip 5th low,and go from 4th hi,to 5th hi..if you try to go from 4th hi,to 5th lo,its like going back to 4th hi,you dont gain anything,,now how confused are you???????lol,hopefully that all made sence,,,good luck...bob Quote Link to comment https://www.bigmacktrucks.com/topic/19174-quadbox-question/#findComment-78300 Share on other sites More sharing options...
leversole Posted May 24, 2011 Share Posted May 24, 2011 The ratios on a TRQ-7220 for example, are such that the ratios are so close together, that shifting would not do much or go backwards...4-Direct is 1.00 ratio4-Hi split is .84 ratio5-Lo split is 1.01 (backwards!)5-Direct is .845-Hi split is .70 So for this trans, you would shift 4-Hi directly to 5-Hi Quote Link to comment https://www.bigmacktrucks.com/topic/19174-quadbox-question/#findComment-78301 Share on other sites More sharing options...
mowerman Posted May 24, 2011 Share Posted May 24, 2011 also generally,when it looks like thier going from 2nd to 4th,on the augsilary its an overdrive transmission ,thats the way thier setup thier actually going from lo to direct,then the up position is overdrive,good luck bob Quote Link to comment https://www.bigmacktrucks.com/topic/19174-quadbox-question/#findComment-78303 Share on other sites More sharing options...
Gmerrill0516 Posted May 24, 2011 Author Share Posted May 24, 2011 Well that helps a little bit but it's not nearly as simple as one might think. Did Mack put out a manual on these things that lays it all out for us new old truck guys? I'll be sending to Mack for anything I can get on the truck once I have it home. I will see a guy Saturday who has an old LTLSW with a triplex. I'll pick his brains while I'm there. Then I will practice until I get it right. Quote Link to comment https://www.bigmacktrucks.com/topic/19174-quadbox-question/#findComment-78364 Share on other sites More sharing options...
HK Trucking Posted May 30, 2011 Share Posted May 30, 2011 Just remember that "lo lo" is not a part of the on road shifting sequence. Lo lo is only for off road use in 1st or sometimes 2nd gear.You shift the compound lo split to direct, then hi split, then upshift the main to the next gear, then downshift the compound to lo split & do the same thing over again. Once you are in 4th hi & ready to upshift, just shift the main to 5th.There are lots & lots of tricks that can be done with those transmissions, and in the hands of an expert it will sound as if the truck has an automatic transmission as it is being shifted thru the gears. Quote "If You Can't Shift It Smoothly, You Shouldn't Be Driving It" Link to comment https://www.bigmacktrucks.com/topic/19174-quadbox-question/#findComment-78680 Share on other sites More sharing options...
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