13 speed deep reduction options

I use the deep reduction all the time when I load and unload or back up. I don't have to work on my drive line and clutch lasts forever. Original tranny lasted 1.5k+ and still have the original back rear at 1.8k. 18 speed would be nice but this old 15 has served me well.

 

I have an '08 Pete with a 15 sp. As I run dedicated OS/OW, I use the deep reduction gears on a daily basis. I routinely gross out around 100-110 k lbs., and sometimes up to 160k. It sure helps to get a heavy load rolling without straining the driveline. Anything under say 80-90k though I rarely reduce unless in sand/mud/clay....

 

An 8ll is an 8 speed. 4 on top 4 on bottom plus a lo gear. (basicaly blue button on the side of the shifter is the lo-lo splitter. It should only be split to low-low when the truck is STOPPED. When needed I would split to lo-lo and start in first (or low) and shift it normal from there, at any time you can move the blue button to direct and it splits around 1/2 gear up. A 13 you can split the top side up or down but not the bottom side.

 

While what kylefitzy says is functionally true, the internals a tad more complicated. All the deep reduction boxes (7LL, 8LL, 9LL, and the 15's) are basically a 5 speed main box with a 3 speed auxiliary section. The 13 and 18's are a 5 speed main with two 2 speed auxiliary sections.

Here's a link that will show you the power flows in the deep reductions: http://www.roadranger.com/ecm/idcpl...=0&Rendition=Primary&&dDocName=RR_TRSM-1500LR

and the 13/18's: http://www.roadranger.com/ecm/idcpl...eased&Rendition=Primary&dDocName=RR_TRSM-0670

I think they start around page 20 or so.

 

if i may add to the OP a eaton fuller RT(O)6613 (technicly a 15) has 5 low gears in deep reductions 1-5 LL

 

Using your logic 9 speeds are technically 10 speeds, and 18's are 20 speeds. It's a13 speed, as the 2 two gears in low are equivalent to 1st and 2nd. And if you look at the ratios, only the bottom two gears are low enough ratios to be true 'deep' gears.

BTW, it's also an antique. And what do you know Packrat posted this long ago: http://www.thetruckersreport.com/tr...on-info-yesteryear-post111033.html#post111033

 

yes i know its an antique, no i didnt know that he posted it

 

I currently have a 15 behind a 3406B and I would take a 13 over the 15 just because the 13 has more progressively higher ratios available -> less rpm drop between shifts. Before some of you click the "post quick reply" button to say that a 15 has more than a 13, please re-read posts by Hammer, Uncleal and Wore Out.

The 15 doesn't get you 5 more ratios below low range. It only gets you one lower ratio. You can start a 15 in 1st gear and skip directly to 6th to get the next higher ratio. A 15 is basically an 11.

The only downside to a 13 that I can see is that the "syncros" seem to wear out, which seems to cause a tickling of the gears when you split.