10 spd vs 13 spd

I would never go below a 13 speed myself, so I would recommend it.
Overdrive is .73 on most 13 speeds, so it would reduce your RPM's by that amount. Normally you drop @300 rpms between direct and overdrive in the top range of gears.

Martin

 

Answered in line

To give you any real info, I need to know your rear end and tire size. Rear end will really determine if a 13 will be a good choice. If your truck is speced for a direct trans, you can run a 13 in 7H (two half gears down from top gear) which is direct and get .25 extra fuel economy. You also have an extra 2 gears if you want to fly when empty. If its specked for .73 or .74 trans, your cruise will not change much, but the 13 will do better on hills.

 

13 speed is much more drivable.

i have been driving 18's for quite some time now im driving a 9 speed and hate it. still gets the job done but so much more drivable being able to split the gears being able to always have it in its optimum operating range rather than having to wind it out further or lug it down lower to go up or down gears. ill never buy another truck with less than a 13.

 

Running those speeds its hard to really get good fuel mileage at all. But having a 13 or 18 imo will help. I have a 475 cat 18spd 3.25 rears. I get 7.5 light, & 6.4mpg heavy at 65mph. I only turn 1300 at that speed. My trip mpg for this trip from Mn to Ct has me at 6.7mpg with 38,000lbs. My old 10 spd would have been around 5.3.

 

A 13 wont help you to much but i'd still say worth the upgrade. The best configuration for you would be a 2.64 rear end (convert it). With that rear end, you can do 65 mph in direct (7H) and then have plenty of speed left over when you use 8L and 8H (varies slightly on tire size). You could do around 88 mph in top gear at only 1400 rpm. 74 mph in 8L @ 1400 rpm. Of course Low becomes first to to the high gearing. If your not pulling steep hills, a 2.64 rear and a 13 would keep your rpms down when flying empty and give you much better mpg. when loaded you can do 65 in direct and get the added mpg of running direct. (@1400 rpm)

These speeds are rough since tire size will factor into it. This is based on a tire that turns 498 times/mile

 

This is wear a 2.64 rear with a 13 speed will shine. You can go 85 @1400 rpm, assuming you have the power and your tires wont explode. (probably cant when loaded, also most tires are rated for 75)

 

on 13 sp, you can stay on 7th gear uphill.

 

A 13 would be a great upgrade and since it looks like you've got a 10 OD now, final drive would be really close to what you have already, so no other mods are necessary since these days all transmissions are the same length.

While its apart, replace both motor mounts you really don't want to do this part with the trans in place. Big $$$ for labor.