13 to 18 conversion

I know the 9spd can be converted to a 13 but have never heard of an 18 conversion. From my research of converting 9-13 it is not cost effective. Better to just swap it out. What are you running that would need an 18 spd?

This may help...

http://www.thetruckersreport.com/tr...9-speed-in-13-speed.html?highlight=conversion

 

theres another post about this if you look hard enough in this section. I think they said something about that it can be done by adding or changing a air line, but the tranny wears out really quick if you do it.

 

the gearing in the back half i beleave is the same all you have to change is the range valve and the shift knob. I have done it before on mack trannys and you just have to change the knob or take it apart and cut out the interlock tang so you can move the splitter in high and low. I am not 100% sure on the fullers but this is what I've gathered.

 

Why would it wear out a tranny? Wear out the shift linkage? Or gearing? Would it be using the wrong clusters or something?
Just curious.

 

No idea, thats just what I read in a post on here. I dont see how it would either, but I can see maybe on the low side it might not me able to handle the torque when you split the gear. But like I said there is another post about this. look back in spring/summer of 2008 posts

 

changing a 9 to a 13 is done by installing another section on the back of the trans a 9 speed really has 10 positions and you should not even use the xtra posistion which would be low gear on the bottom side as it's not designed for that . an 18 speed is designed from scratch to split the low side of the trans. i would assume trying to split the bottom side of a 13 would go kaboom!

 

112racing is right. The splitter part of the trans on a 13 speed doesnt see use until the trans is on the high side. This means the splitter portion doesnt see use until the engine torque is greatly reduced. The splitter portion on an 18speed will see use in the high and low side of the trans. This means the splitter must handle the torque being multiplied in the low side of the trans.

I dont know how the splitters are different on 13 vs 18 speeds but an 18speed splitter is subjected to twice the torque than that of a 13 speed.

 

The one in my 98 is a RTLO 16713A It blew up about 15 months ago partly due to a countershaft bearing failing and somewhere along the way before I bought the truck some cheap-o aftermarket made in Brazil gears were installed. I had only made 2 trips with it since I bought it and put maybe 5000 miles on it. The transmission had a tag on the case with a rebuild date from about 16 months before I bought the truck. I asked about converting it to an 18 speed when it was getting repaired and was told that it won't work without changing a lot of internal stuff. You can change the shifter knob and shift a 13 like an 18 but it will not last long due to the increased torque load on the components when the trans is in low range. That is the same reason they tell you not to put the shift lever in the first gear position unless you have the shift knob in low range. If you do that while in direct or OD, it will fail sooner due to too much load on the components. If I was going to do it again, I would have just bought a factory re-man unit off the shelf and paid the extra cost to go from 13 to 18 speed. I was down over a week waiting for my transmission to get done so I could pick it up and reinstall it. The difference of 1-2 days down time compared to over a week would have easily covered the difference between fixing mine and buying an 18 speed off the shelf. We wound up having to order parts to fix mine and thats where the wait came about. Eaton-Fuller has a cool website called roadranger where you can download all the parts books and manuals for free, you could probably find out about converting yours on there too, I didn't look. What ever you do, in my opinion, pay the extra cost for genuine parts its not that much more and a lot cheaper than doing it twice because the cheap stuff didn't work right the first time. I used the real factory stuff and it is still working perfectly 150,000+ miles later.

 

As far as more torque going through the splitter in low range that is incorrect. The low range gear set is the last set of gears in the back half after the gear reduction in low range the power goes right out the main shaft and to the yoke. All the splitter would do is change the gear ratio after the main box. But like I said I'm not sure of any other issues that might be run into.