burnin oil Posted November 12, 2012 Share Posted November 12, 2012 Parts truck has a TRD-72 9 speed OD trans. Anyone know the ratios? Debating sticking it in the L model istead of the TR-150 and keep the Auxiliary trans. Spent an hour looking and couldn't find the answer, the wiki page has an error on this trans when I down load it. Quote Link to comment Share on other sites More sharing options...
Green Dash Posted November 12, 2012 Share Posted November 12, 2012 The link below can be found by clicking the Wiki button at the top of this page. Lots of great info there. Your tranny would be a TRD-720 since it's an OD.http://www.bigmacktrucks.com/index.php?/tutorials/article/37-b-model-transmission-data/ Quote Jim Link to comment Share on other sites More sharing options...
burnin oil Posted November 12, 2012 Author Share Posted November 12, 2012 Thats where I had the problems with the wiki. The duplex section comes up with 2 sets of ratios and four transmissions listed. From what I have read the back box is OD and the main is direct for the 9spd. The tag on the visor says 9spd OD but the number on the trans is TRD-72. From my searching on here I got 5 hi as 1:1, .78:1, and .69:1. No idea what is really correct. Quote Link to comment Share on other sites More sharing options...
Superdog Posted November 12, 2012 Share Posted November 12, 2012 Thats where I had the problems with the wiki. The duplex section comes up with 2 sets of ratios and four transmissions listed. From what I have read the back box is OD and the main is direct for the 9spd. The tag on the visor says 9spd OD but the number on the trans is TRD-72. From my searching on here I got 5 hi as 1:1, .78:1, and .69:1. No idea what is really correct.the trans. might have been changed at sometime. Quote Link to comment Share on other sites More sharing options...
Green Dash Posted November 12, 2012 Share Posted November 12, 2012 I would think the number on the trans would be correct. Quote Jim Link to comment Share on other sites More sharing options...
burnin oil Posted November 12, 2012 Author Share Posted November 12, 2012 Is there any way to ID them positively besides driving or dropping the trans from the truck? I think the main is direct with an OD aux section instead of a direct/under setup. Maybe a number on the rear section or different bolt/casting arrangement? I am by far not an expert on these things but do have an understanding on how it works. Quote Link to comment Share on other sites More sharing options...
Red Horse Posted November 12, 2012 Share Posted November 12, 2012 Thats where I had the problems with the wiki. The duplex section comes up with 2 sets of ratios and four transmissions listed. From what I have read the back box is OD and the main is direct for the 9spd. The tag on the visor says 9spd OD but the number on the trans is TRD-72. From my searching on here I got 5 hi as 1:1, .78:1, and .69:1. No idea what is really correct.When in doubt, get a rag, get under the truck, and read what is stamped on the driver side of the trans case. Quote Link to comment Share on other sites More sharing options...
burnin oil Posted November 12, 2012 Author Share Posted November 12, 2012 When in doubt, get a rag, get under the truck, and read what is stamped on the driver side of the trans case. Am I nuking this in thought. If there are several versions of the Duplex transmission wouldnt the front box be stamped as what the high gear was regaurdless of what aux section is bolted to the rear? That way the main would always denote direct or OD no matter if the rear is under drive or over drive splitter?Correct me if I am wrong but are the L model boxes under driven rear section with the standard transmissions being OD rear box? This would give a TRD-720 2 OD gears correct? Quote Link to comment Share on other sites More sharing options...
burnin oil Posted November 14, 2012 Author Share Posted November 14, 2012 Bringing this back to the top. I am still curious to the way the rear box works (under/direct or direct/over) and how Mack id's the transmissions (ie is direct or OD of the main what makes the desgnation on the side of the transmission). Quote Link to comment Share on other sites More sharing options...
Maddog13407 Posted November 14, 2012 Share Posted November 14, 2012 the box would most likely be correct, not really a way of knowin unless u drive it. someone could have changed the tag in the cab or busted the front case and used another one or totally changed the cab. we used a case for my B613 from a quadbox and put duplex gears in it. regardless of a 10 speed direct or 9 speed overgear the front gears i believe are the same. the are only different in a double over quad or triplex where 4th and 5th are different. if you drive it and you cant split 5th gear with the high or low or 5th low your going the same speed as 4th high, then its a 9 speed overgear TRD720. if you can split 5th gear with the high and low lever then its a 10 speed direct. they also made a 10 speed overgear just to confuse you. the old guys call these ''mudsticks'' and were generally in 10 wheel dumptrucks. the newer 10 speed directs (around the mid to late 60's) the number was changed and it went to TRD722 and i believe had different ratios. also i believe it would be low or under and high which would be direct. Quote Link to comment Share on other sites More sharing options...
BOB DINGSDALE Posted November 14, 2012 Share Posted November 14, 2012 burninoil:I have a brochure on a 1952 LJT-G with 3 trans listed.TR 720 standard 0.78 in 5th,2 optionals-TRD720,10 forward 2 reverse,10th-0.78-9th 1.04,8th-1.00 7th-1.33,etc to basement.TRDX 720 10th-0.78,9th- 1.85,8th-1.00,7th-2.38 etc to basement.In 1952 a LJSW D the duplex was a TR150 with 10th-0.77,9th-1.07,8th-1.00,7th-1.38,etc.Hope this sheds somelite on your trans question. Quote Link to comment Share on other sites More sharing options...
burnin oil Posted November 15, 2012 Author Share Posted November 15, 2012 Thanks guys. I have no real plans to drive it. The truck is going to be parted out and I am debating if it is worth my while to pull the trans and install it in my L model. If I put the duplex infront of my L's factory auxiliary trans I will have a really good road speed with the donor 4.65 rear end. If the trans is a direct top gear I think that I would be shooting myself in the foot. Quote Link to comment Share on other sites More sharing options...
Brian Blaylock Posted November 15, 2012 Share Posted November 15, 2012 Hey Burnin oil if you are going to take the transmission out of the truck it is then easy to check to see if it is direct or overdrive mark the input shaft on very top and do the same to output shaft put it in high gear have someone turn input and watch output if they make a full revolution at the same time it is direct if the output makes a full revolution before the input it is an overdrive Quote Link to comment Share on other sites More sharing options...
burnin oil Posted November 16, 2012 Author Share Posted November 16, 2012 Thanks Bryan. I know that trick well. I was hoping not to pull it if I didn't have to just to check the ratio out but it looks like that is about the only way to tell for sure. I was hoping that you could identify the rear box like you can on an Eaton. Just be a little more work. Quote Link to comment Share on other sites More sharing options...
fifth wheel Posted November 16, 2012 Share Posted November 16, 2012 A TRD 150 and a TRD720 just about identical, TRD 150 in 5th = .77, TRD 720 in 5th= .78 All duplex compounds direct in High, underdrive in LowFW Quote Link to comment Share on other sites More sharing options...
burnin oil Posted November 16, 2012 Author Share Posted November 16, 2012 All duplex compounds direct in High, underdrive in LowFWThanks fifth wheel. That is exactly what I wanted to know. Quote Link to comment Share on other sites More sharing options...
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