RTLO 18913A questions

It's a double overdrive.
There's no cons , all pros over your 10 speed

 

Yes, the O in the part # means overdrive. Technically it is a single overdrive, which is 8th gear. In reality, since you can split the high range, you have 2 overdrive ratios, 8th low (0.86) and 8th high (0.73).

 

Doesn't the "9" part of it mean double overdrive? I know the O means overdrive as well

 

Being double overdrive instead of single overdrive he'd need lower ratio diffs or the truck would be too fast, that's my take on it anyway

 

I never really paid much attention to the 9, but since you asked I looked in the book and that is the design level.

 

9 is the build level, a 16713 would have the same ratios.

The 15210C should have a .74 overdrive, the change to .73 will not require a rear end ratio change.

 

18918 has the fine spline output.
The 18718 or any 7 for that matter are course spline output.
The 9 series came out because guys were having problems with the yolks coming loose.
Apparently the fine spline don't wear like the course 7 series.
I do know that to get a yolk off a 9 series that's been on a long time, sometimes have to be cut off with a torch.

 

Tbh, I don't know anything about the 10 speeds, but when I wanted to change my Spicer for a Roadranger, I was told you couldn't get a single overdrive in anything above the 1600 ft/lb series. As I wanted 2200 ft/lb (RTLO 22918B) I had to settle for double overdrive and re-ratio the diffs, which wasn't a bad thing as it happens because now I've got a super-low Lo gear. (4.56 diff ratio). Perfect trans combination for my line of work.