steve p Posted September 8, 2012 Share Posted September 8, 2012 i have a14609b ratio witha 14613 b aux rear which gives me a under split in top five ,i had to shorten the drive shaft by 3 " ,far better to drive than the nine speed .[350hp 5.32 rears 1800@100kph 22x11r tyre Quote Link to comment Share on other sites More sharing options...
Bollweevil Posted September 8, 2012 Share Posted September 8, 2012 An RTX14609B is a .73 overdrive. The 14613 0verdrive transmission is made up of a direct 9 speed with an overdrive rear box which gives you a .87 not a .73 final drive ratio. The 14609B is over driven in the front box, the 14613 is over driven in the rear box. By adding the 14613 Rear box you compound the overdrive to a .63 final drive. Other than a rear box, a matching auxiliary drive gear is all you need to make the swap. You wont change anything at all as far as ratios in the first five gears. Highway speed in 9 direct will remain the same. You might find something you can use as you start splitting the top four, probably not. You could possibly set your hair on fire. 1 Quote Link to comment Share on other sites More sharing options...
dds92780 Posted September 8, 2012 Author Share Posted September 8, 2012 First of all i wanted to thank ALL of YOU for sharing your superior knowledge of all this so far! The truck i drive is a RD mack with a e7 350 in it topping out at 1800 rpm. i have 22.5 tires on it. A RTXF14609B trans with .73 overdrive. I have 442 rears. From what i gather so far is that if i can get a 13 speed in it and change an auxillary to .63 overdrive i would have a setup that still does what mine does but split the top gears.Would this give me a lower crusing rpm in top gear at 65?would my top speed still be 65?would my low hole still be the same?I was looking at a chart for the 8ll and it does look like a good trans for the low hole but on top end looks the exact same for every ratio up till 8Is doing this swap going to increase mpg at all? Quote Slow and Steady Wins the Race! Link to comment Share on other sites More sharing options...
oilburner Posted September 8, 2012 Share Posted September 8, 2012 First of all i wanted to thank ALL of YOU for sharing your superior knowledge of all this so far! The truck i drive is a RD mack with a e7 350 in it topping out at 1800 rpm. i have 22.5 tires on it. A RTXF14609B trans with .73 overdrive. I have 442 rears. From what i gather so far is that if i can get a 13 speed in it and change an auxillary to .63 overdrive i would have a setup that still does what mine does but split the top gears.Would this give me a lower crusing rpm in top gear at 65?would my top speed still be 65?would my low hole still be the same?I was looking at a chart for the 8ll and it does look like a good trans for the low hole but on top end looks the exact same for every ratio up till 8Is doing this swap going to increase mpg at all?If you can change the aux gear like one of the guys said on your trans and add a back box off a 14613 speed you will make it a double overdrive, yes you will gain more top end and can split the last 4 gears, like i said i ran a superliner with this trans and it helped it out on the top end about 15 or 20 miles an hour, but if your engine will only turn 1800 you would probely lung bad in high gear you would proberly want to have the engine rpm rasied to 2100 or 2200. Yes your low hole would still be the same it would not effect that. The superliner had a mack 9 speed in it to start with which was a overdrive but the truck was gearbound on the freeway, doing the swap helped it on the highway, but it did have a 3406b 400 hp cat in it. I mention the 8LL because i thank your trans is what it is made from they just add a deep reduction box on it they both have a good 1 gear and the ratio going up in the gears are the same, with the big hole overdrive. In my opinion i would talk to a good tranny shop if i could find one and see if just putting a 13 speed back box on your transmission is the way to go, that way you keep you low hole instead of getting a RTO14613 and fliping it which would help you on the top end but you do loose the low hole when you flip it because the ratios in each gear are high after this the ratio between them stay the same so what you gain on top you loose on the bottom. Quote Link to comment Share on other sites More sharing options...
oilburner Posted September 8, 2012 Share Posted September 8, 2012 If you can change the aux gear like one of the guys said on your trans and add a back box off a 14613 speed you will make it a double overdrive, yes you will gain more top end and can split the last 4 gears, like i said i ran a superliner with this trans and it helped it out on the top end about 15 or 20 miles an hour, but if your engine will only turn 1800 you would probely lung bad in high gear you would proberly want to have the engine rpm rasied to 2100 or 2200. Yes your low hole would still be the same it would not effect that. The superliner had a mack 9 speed in it to start with which was a overdrive but the truck was gearbound on the freeway, doing the swap helped it on the highway, but it did have a 3406b 400 hp cat in it. I mention the 8LL because i thank your trans is what it is made from they just add a deep reduction box on it they both have a good 1 gear and the ratio going up in the gears are the same, with the big hole overdrive. In my opinion i would talk to a good tranny shop if i could find one and see if just putting a 13 speed back box on your transmission is the way to go, that way you keep you low hole instead of getting a RTO14613 and fliping it which would help you on the top end but you do loose the low hole when you flip it because the ratios in each gear are high after this the ratio between them stay the same so what you gain on top you loose on the bottom.Oh yea and if you have bud wheels you can go with a 11r24.5 tire and it will help you on top end as well. Quote Link to comment Share on other sites More sharing options...
dds92780 Posted September 8, 2012 Author Share Posted September 8, 2012 very good info thanks. so it looks like i can keep my existing trans and just add a back box to make it a 13spd with the same gearing that way i can get more out of it on hills? i dont do a whole lot of highway driving. i do mostly dump work but when i find myself on the highway or a main road i try to do 55mph or so but crusing at 60 or so with the rpms down lower would help Quote Slow and Steady Wins the Race! Link to comment Share on other sites More sharing options...
dds92780 Posted September 8, 2012 Author Share Posted September 8, 2012 After researching more i have looked into the RTLOF 14713A and it seems to be the perfect fit for my setup. i get a first gear of 8.64 vs the 7.47 i currently have giving me a better low hole. low gear sacrifices .25 which it makes up in for 1st gear though so i like it. im thinking though if i get this trans with my already low top end 442s then low gears would be even shorter but almost the same in the top gears it shows with the abiltiy to split them on the high side. does this seem like a good setup? or do i gotta switch the rear ends too? i wish i would of known about all this stuff before choosing a truck ;( Quote Slow and Steady Wins the Race! Link to comment Share on other sites More sharing options...
dds92780 Posted October 24, 2015 Author Share Posted October 24, 2015 Ok I just researched more and im even wondering if my transmission can be converted to a 13 speed with some sort of back box upgrade I call it in Fullerton Road Ranger to talk to a technical person but they didn't know if I could or not all they did was tell me what transmission they would recommend after researching more on my own online about people that have done swaps it seems that the only ones that have the letter C at the end are convertible what can you do with a B Series transmission is there a way to make this current transmission into a 13 speed by just adding some sort of kit.I have no idea where to begin to look Quote Slow and Steady Wins the Race! Link to comment Share on other sites More sharing options...
dds92780 Posted October 27, 2015 Author Share Posted October 27, 2015 Anybody have any info regarding my last statement? Quote Slow and Steady Wins the Race! Link to comment Share on other sites More sharing options...
Dirtymilkman Posted October 28, 2015 Share Posted October 28, 2015 When I was in school we were told only the c could be made into a 13spd. And if you wanna swap trannies, you might as well get a 18spd Quote Link to comment Share on other sites More sharing options...
Dean thacker Posted October 27, 2019 Share Posted October 27, 2019 On 9/6/2012 at 9:41 PM, theakerstwo said: You can convert a 9 speed eaton drect only. to a 13 speed.Get undertrans and get trhe model # off of the plate and post it and i cantell you what it is. glenn Can I take the rear box off my 8 LL and put on my 9 speed and make it a 13 1 Quote Link to comment Share on other sites More sharing options...
RickJany Posted January 11, 2021 Share Posted January 11, 2021 RT 12609A - Can this transmission be converted to a 13 speed? Quote Link to comment Share on other sites More sharing options...
luke andres Posted January 12, 2021 Share Posted January 12, 2021 correct me if im wrong but doesnt a mack 13 and 18 speed tranny run a .60 overdrive probably not the cheapest route but a possibilty if found a good used one Quote Link to comment Share on other sites More sharing options...
theakerstwo Posted January 12, 2021 Share Posted January 12, 2021 2 minutes ago, luke andres said: correct me if im wrong but doesnt a mack 13 and 18 speed tranny run a .60 overdrive probably not the cheapest route but a possibilty if found a good used one .71 Quote glenn akers Link to comment Share on other sites More sharing options...
luke andres Posted January 12, 2021 Share Posted January 12, 2021 thats right its the 20 series that have the .60 overdrive 2060 2070 2080 etc. Quote Link to comment Share on other sites More sharing options...
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