Converted 9 sp to 13 sp into an 18sp?

Yooper, I'm leaning more and more towards saying give it a shot! If you were heavy-hauling or something where you might spend a lot of time using the newfound gears in a high torque situation, that gear with bearing would worry me about why it's there. But as gl noted, it carries a higher torque load in high/low-split, so I'd be doing some parts pricing to further assess the feasibility. You could try to get more info from Eaton, but your not likely to get much there. Wouldn't help sales of 18's to let that info out if it is true.Good luck!

 

I have a good 13 speed that I plan on installing in one of my trucks that currently has a 9 speed. I'm definitely gonna try it if I can ever get around to switching it.

 

Hey Glenn, we made a logical mistake when thinking about gear loading. When looking at the flow through a gearset, anything downstream doesn't matter; imagine the output shaft locked in place, nothing beyond the gear being considered has any effect on the torque on that gear, so range position doesn't matter. Low split would still seem to be the heavier loading as it is an underdrive.

I do think, though, I may have stumbled upon the reason for the bearing on the splitter gear in the 18. In high range, the splitter gear is coupled to the output shaft via the range mechanism; in low range it is not. It would seem that here is the issue, for only in low range/ high split is that gear under load and isolated from the range clutch.

I see you edited last night's post, but I'll answer anyway. There is some difference somewhere in the actuation system beyond the mechanical shift knob split lock. If you are in 4lo in a 13, and lift the range selector w/o moving the lever, you can move the splitter button. But the splitter will not operate until after the range change is physically completed. This shouldn't be too hard to defeat with a little rerouting of air lines.

In reverse power flow, high range/ low split is max splitter load combo.

hope this helps, Jack

 

I respectfully disagree. I think what's downstream matters plenty. If you daisy-chained enough range sections together between the splitter section and the output shaft and had them all in low range, you could eventually move a truck by turning the splitter gears with a hand crank. Obviously the truck would move very slowly, but stress on the splitter gears, the hand crank and your hand would be very small. If you had the output shaft locked down in the same scenario, yes nothing would move, but with enough mechanical advantage, you could hand crank the splitter section and break the teeth on the gears closest to the output shaft.

I'm guessing you can do that in any stick position? But yes, this should be doable.

Edit: I wonder if the splitter behaves that way because a range change is happening too? With the 18spd knob a splitter-only shift might work fine?

Glad to hear you say that. I just can't seem to get my brain around that one. It's like I wanna build a model

Cheers,
-Glenn

 

Glenn, I'm not being clear enough. You're right on getting enough reduction, you can move anything by hand. But if you have a constant torque input, only the gears in front of the gearset you're examining have any effect on the load of that gearset. You're looking at it from a constant output perspective. All those gears downstream definitely effect what you can do with the input, but they don't change the input, they change how fast a given input will move a load. Go back to the stalled out condition, with you pulling for all your worth on the input. Doesn't how many reductions are downstream, only the reductions upstream effect the torque on that gearset.

No, there is some mechanism that requires a range change to occur before the splitter will operate. The old 13's only had three airlines to the shifter, new ones have four. The air supply to the splitter knob comes back up from the transmission and is only suppied when in high range.

Yeah, in low range the output shaft has a major overdrive to the aux countershafts. So when the aux mainshaft is driven by the output at 1:1 in high range, only in low split does the splitter gear carry any load at all. See it now?

 

I actually looked into this a while ago, and the correct answer is no.

Here's why:

The transmission in question is a 9 speed convertible. It converts by swapping the 2 speed brownie for a 3 speed brownie. The splitter doesn't get as much torque in high range, but in low range... Crunch!

Now; if you start with a 13 speed, provided it isn't the light 13, changing the knob is all you need. Those transmissions aren't very common though, since you can spec a truck for a 9 convertible rather cheaply, then $200 conversion is you want the 13. Many companies do this, so they get the reliability (low maintenance) of the 9 speed. It also keeps the drivers from being freaky with their driving. They then convert it for sale, because it'll increase resale value.

I was going to do this, so I contacted Eaton to make sure it was not a half baked idea. They told me all of this. If you want to be able to swap between 13, and 18, you have to start with either of those transmissions.

The 9 speed conversion is kind of a hack to begin with. You can only take it just so far.