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Just picked up a 97 379 with 3406b 4mg, eaton 40k rears, 3:70 gears and what i was told was a eaton 13 double over. First question; 13 d/o I thought the big hole was against the dash, with mine its a normal H pattern with over drive toward the sleeper? I was told it was like a 41% over drive. On the bottom side running 75mph rpms are 1775 and when i hit the big hole rpms drop to 1490 so with that said i cant question the fact if it is or is not a 13 double over i just have never drove one set up in the H pattern as mention and this leads to 2nd question; this will be kind of hard to explain so bare with me a min.......question has to do with splitting the gears on THIS trans and to me its a weird set up....goes like this, R-1--3 (this would be the bottom side)
L -2--4
(And this is the top side) --6/7--10/11 and im doing this so i can ask this
5-8/9--12/13

question......when splitting 6/7 or 8/9 i can pull in neutral split and return in gear as i have always done with any H/L tranny however with this tranny once you make it to 10/11 and 12/13 i must leave it in the hole while splitting the gears or else I'm hitting the shoulder and having to start over cause it will NOT allow me to return to gear cause everything in tranny is spinning and wont stop till road rpms are slowed way down......this means if coming from 11 gear i have to leave it on top side and go to 13 then split to have 12th gear......has this tranny had some kind of hack job or is this norm and my last 15 yrs driving has just been way to simple for me? Can someone give me the run down has to how this Transmission is set up so I can feel better.....:stupid
 

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Just picked up a 97 379 with 3406b 4mg, eaton 40k rears, 3:70 gears and what i was told was a eaton 13 double over. First question; 13 d/o I thought the big hole was against the dash, with mine its a normal H pattern with over drive toward the sleeper? I was told it was like a 41% over drive. On the bottom side running 75mph rpms are 1775 and when i hit the big hole rpms drop to 1490 so with that said i cant question the fact if it is or is not a 13 double over i just have never drove one set up in the H pattern as mention and this leads to 2nd question; this will be kind of hard to explain so bare with me a min.......question has to do with splitting the gears on THIS trans and to me its a weird set up....goes like this, R-1--3 (this would be the bottom side)
L -2--4
(And this is the top side) --6/7--10/11 and im doing this so i can ask this
5-8/9--12/13

question......when splitting 6/7 or 8/9 i can pull in neutral split and return in gear as i have always done with any H/L tranny however with this tranny once you make it to 10/11 and 12/13 i must leave it in the hole while splitting the gears or else I'm hitting the shoulder and having to start over cause it will NOT allow me to return to gear cause everything in tranny is spinning and wont stop till road rpms are slowed way down......this means if coming from 11 gear i have to leave it on top side and go to 13 then split to have 12th gear......has this tranny had some kind of hack job or is this norm and my last 15 yrs driving has just been way to simple for me? Can someone give me the run down has to how this Transmission is set up so I can feel better.....:stupid
What you have is an RTO, or RTOO if indeed a double OD. What you are used to is a RTLO....BIG DIFFERENCE. You CANNOT preselect a splitter change with the RTO or RTOO, or you have to start over as you explained. These old 13's are nothing compared to the RTLO's because the aux main shaft is not splined to the main box main shaft. The L in RTLO is "Low Inertia", meaning driver friendly and easier to shift.
If your RTOO has the X top cover, then it will still shift like a regular "H" pattern...not turned around "up at the dash". The easiest way to tell which cover is look on top in front of the shifter...if it is an X cover, you will see a 3/4 nut or possibly a round dowel sticking up. This holds the "Z" bar or lever that makes it an X cover, but actually its reversing the shifting inside.

RTOO is .62 or 38% overdrive. RTLO is .73 or 27%.
 
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Just picked up a 97 379 with 3406b 4mg, eaton 40k rears, 3:70 gears and what i was told was a eaton 13 double over. First question; 13 d/o I thought the big hole was against the dash, with mine its a normal H pattern with over drive toward the sleeper? I was told it was like a 41% over drive. On the bottom side running 75mph rpms are 1775 and when i hit the big hole rpms drop to 1490 so with that said i cant question the fact if it is or is not a 13 double over i just have never drove one set up in the H pattern as mention and this leads to 2nd question; this will be kind of hard to explain so bare with me a min.......question has to do with splitting the gears on THIS trans and to me its a weird set up....goes like this, R-1--3 (this would be the bottom side)
L -2--4
(And this is the top side) --6/7--10/11 and im doing this so i can ask this
5-8/9--12/13

question......when splitting 6/7 or 8/9 i can pull in neutral split and return in gear as i have always done with any H/L tranny however with this tranny once you make it to 10/11 and 12/13 i must leave it in the hole while splitting the gears or else I'm hitting the shoulder and having to start over cause it will NOT allow me to return to gear cause everything in tranny is spinning and wont stop till road rpms are slowed way down......this means if coming from 11 gear i have to leave it on top side and go to 13 then split to have 12th gear......has this tranny had some kind of hack job or is this norm and my last 15 yrs driving has just been way to simple for me? Can someone give me the run down has to how this Transmission is set up so I can feel better.....:stupid
As far as shifting goes, you answered your own question. If you are in the high side, button forward, and you want to upshift and go back to direct, you have to go ahead and upshift, then pull the button back and raise RPMs to meet the gear. Anytime you move the splitter in neutral with an old RTO or RTOO, it will lose syncronization and you either have to pull over and stop, or hold the clutch brake and make the countersahfts stop turning and the splitter will go back in. Hope this is not confusing....
 
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SLEDMAN....you hit the nail on the head....I appreciate the quick reply. Thanks again!
Heres a formula to find your speed and RPMs....

Engine RPM x 60 / (Axle Ratio x Tire Revolutions per Mile x Transmission Ratio) = Top Road Speed (MPH)
 

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Man. Trans 2wd Enthusiast
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185 Posts
technically isnt the RTOO a triple overdrive? in the main box, its like a 9 speed over, correct? then you have the overdrive splitter, so in 7th there is one overdrive ratio and in 8th there is two overdrive ratios.


nifty old transmissions for sure! :) got to spend all of corn harvest rowing gears in the ol RTO9513 behind the 1674 cat in the 74 pete. takes more finess than what I have to guarantee grind free shifting all day when not using the clutch. not that I use it anyhow, i just get to wince whenever I get the shift wrong.
 

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technicly it is a double over drive, an overdrive ratio (.73) being overdriven by 17 % or about.62,it has 3 overdrive ratios, but one is direct being overdriven, next is an overdrive in the main being direct driven , then over in the main being overdriven thus double overdrive. Unlike the rtlo 13 which has an under drive splitter . overdrive in the main but that is top gear, the low side of the split is underdriven so even though there is 2 ratios with overratios ther is no doubling.
this is argued till the cows come home . :bdh
 
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