DodgeMan Posted December 28, 2011 Share Posted December 28, 2011 (edited) I recently bought a B81 SX with a quad box. I crawled under it to see what trans number was on it and it was stamped TRD720 witch is a duplex transmission to the best of my knowledge. I`m wondering is it was possible to use a duplex case and change the gears out to make it a quad box case....The truck is def a quad box no if ans or butts. Edited December 28, 2011 by DodgeMan Quote Link to comment https://www.bigmacktrucks.com/topic/22346-main-case-interchange-trd720/ Share on other sites More sharing options...
Rob Posted December 28, 2011 Share Posted December 28, 2011 I recently bought a B81 SX with a quad box. I crawled under it to see what trans number was on it and it was stamped TRD720 witch is a duplex transmission to the best of my knowledge. I`m wondering is it was possible to use a duplex case and change the gears out to make it a quad box case....The truck is def a quad box no if ans or butts.The complete rear housing is different by about six inches in length. There are also different gearings available. You would be best to purchase another trans.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/22346-main-case-interchange-trd720/#findComment-95681 Share on other sites More sharing options...
DodgeMan Posted December 28, 2011 Author Share Posted December 28, 2011 Thats why im confussed on why its stamped trd720 on the main case. Mabe just the main case was changed. It is Deff a 5 and a 4 trans.Could you send me lenghts on the casses?? Quote Link to comment https://www.bigmacktrucks.com/topic/22346-main-case-interchange-trd720/#findComment-95683 Share on other sites More sharing options...
Rob Posted December 28, 2011 Share Posted December 28, 2011 Thats why im confussed on why its stamped trd720 on the main case. Mabe just the main case was changed.It is Deff a 5 and a 4 trans.Could you send me lenghts on the casses??For the most part the front boxes were the same. It is entirely possible the rear section is original to the truck and the front changed.Is the center section, (main case) aluminum, or cast iron? Most quadruplexes were iron front and rear. I can get you some measurements tomorrow when I'm at the shop.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/22346-main-case-interchange-trd720/#findComment-95685 Share on other sites More sharing options...
DodgeMan Posted December 28, 2011 Author Share Posted December 28, 2011 OK thank you sir. I beleive there both iron cases. Both have blue pain on them like they where out at some time and engine has original green. Quote Link to comment https://www.bigmacktrucks.com/topic/22346-main-case-interchange-trd720/#findComment-95689 Share on other sites More sharing options...
Rob Posted December 28, 2011 Share Posted December 28, 2011 It should be an iron case without an "L" in the model number. Some of the ratios were so close it is hard to tell what is in there especially if something has been changed. I believe all the main cases measured the same as far as length. I don't know about internally. The Duplex, triplex, and quadraplex are readily discernable as to which by looking at them externally.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/22346-main-case-interchange-trd720/#findComment-95691 Share on other sites More sharing options...
Maddog13407 Posted December 28, 2011 Share Posted December 28, 2011 they are the same from case. someone probably split the case and bought one from Mack or had one laying around. my B613 had a cracked case and we stripped out a worn out quadbox and put the duplex gears in it and the duplex back half on it.the aluminum thing i have never figured out. have sen B61LT's with half case aluminum, both cases aluminum front and back and some just the top cover. also seen some aluminum top covers front and rear on quadboxes and triplexes that werent even in Lt trucks. sometimes i think Mack used whatever was handy lol. Matt Quote Link to comment https://www.bigmacktrucks.com/topic/22346-main-case-interchange-trd720/#findComment-95706 Share on other sites More sharing options...
DodgeMan Posted January 29, 2015 Author Share Posted January 29, 2015 Thanks guys.... Quote Link to comment https://www.bigmacktrucks.com/topic/22346-main-case-interchange-trd720/#findComment-276473 Share on other sites More sharing options...
HarryS Posted January 29, 2015 Share Posted January 29, 2015 Dodgeman, If you are looking for a case I have a TRD 72 (Duplex) complete transmission. Harry Quote Link to comment https://www.bigmacktrucks.com/topic/22346-main-case-interchange-trd720/#findComment-276477 Share on other sites More sharing options...
DodgeMan Posted February 1, 2015 Author Share Posted February 1, 2015 Not at the moment Harry. But I won't no more until the snow melts and I can start working on the old Mack again.I will keep it in mind tho...Thanks Paul Quote Link to comment https://www.bigmacktrucks.com/topic/22346-main-case-interchange-trd720/#findComment-276888 Share on other sites More sharing options...
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