Pros/Cons of Converting 9-speed to 13-speed?

RTLC1609E is direct in top gear.. it is not listed in your partial chart there look up the full ratio chart and you will see it

 

The charts I posted weren’t directed at your post, rather to support what Powder Joint stated that the final ratio doesn’t change by converting to a 13. This is true with the DD transmission you referenced. Also I assumed (And probably shouldn’t have) that the OP and the discussion drifted somewhat toward the question of fuel mileage and OD transmissions rather than DD, or for that matter UDs. I could have used the expanded chart, but felt it was to large for my purpose. Sorry I did not explain my purpose.

 

All in the world a 13 speed is, is a 9 speed with a extra box on the back that splits the gears. The 13 speed box is a under and direct 2 speed box, so you don’t gain any overdrive by converting a 9 to 13.

The 15 speed transmissions are much the same, they just take a 10 speed trans to convert to 15.

For years, Eaton/Fuller made two basic transmissions, a 9 and a 10. Every other transmission is a variation of those. Even the 9 and the 10 are very similar, you just don’t hit the first hole on the high side of the 9.

 

I was going to hire on with a decent sized outfit that ran 18's. I mentioned that I usually just split the top unless I need to. He said that shifting that way ruins the syncros and it was forbidden at that company, had to go through them all.

Later hired on with a company that had a 13 in the truck they assigned me and the driver trainer didn't know how to split so he ran it as a 9. The splitter in that truck was unreliable at first until it started being there for me, or maybe I was learning how to deal with it's quirks.

 

He obviously has zero clue about transmissions then. Eaton Roadrangers have only 1 synchronizer and its for the range shift. It only ever gets used on the 4-5 shift and 5-4 shift. It ain't hurting anything.

 

If that is the case I better go ahead and get me a new tranny, cuz I have gone and ruint mine several years ago, but just now found out. lol

It is not a quirk on the 13 you dealt with. The splitter works different on 13 and 18's, you are suppose to be able to preselect on the 18 and not on the 13, both work well as far as I am concerned.

 

Splitter should never be preselected on either transmission. There is no neutral interlock like the range shift has. As soon as you hit that splitter button, the air cylinder is trying to force a split shift. Just causes extra wear on the splitter shift fork and sliding gear.

 

the amount of wrong information in this thread is enough to make you want to beat your head against a wall....lol

but to the original question

if you have the convertible 9 speed. do it, likely wont gain much in mpg but it will be a lot nicer to drive very simple deal to convert it.

if you have a regular 9 speed it will be a fair bit of parts and labor and a new driveshaft. if your hauling under 80k eh would be nice to have a 13 but won't help you that much ether. and your probably looking at at least a few grand to do it.

 

Actually with the rtlo 13&18 Eaton says you MUST preselected the splitter. Ran across a you tube video recently with the Eaton engineers giving a tutorial, and they were very explicit.

This is a change from previous practices on older generations of 13 & 18 s.

I would provide a link for you @AModelCat but I am too old school to know how to do it!

 

No cons to driving a converted 13 speed.