13 speed 2.79 rears

Here is an article from the Pittsburgh Power guys:

http://www.tenfourmagazine.com/PerfZone/2009/6.html

 

It will work you will just have to cruise down in direct 11th gear instead of up in the top 2 OD gears. So you'll be up in 7 over or whatever gear its considered I have an 18 so it'd be 7 over on my trans.

 

As long as you have the low end to start a load nothing says you gotta cruise in high gear. I have a double over but gets me in trouble financially when I use it. I always drop to direct for 6percent grade or more but I try take care of my rig. Most times I cruise in 7th over or 8th direct when loaded. Just cause its there don't mean you have to use it. BTW if you find a 16 series 13 speed for 1200.00 I would like to know where I will take two if they have any more just cause.

 

Actually, running that 13 in direct will also give you (slightly) better mileage, as you are now running direct thru the trans, less drag, (more drive line efficacy) also you tranny will run cooler in direct, less bearing surfaces in play.

 

Whats the model number of the trans you have now? I assume its an over drive trans? You trans final ratio is either .73, .80 or .86. most likely .73 but you would need the trans model number to be sure. A 13 has a final ratio of .73 and a 8Low ratio of .86. If your top gear now is .73 the top in a 13 will be the same. If your top now is .86, 8Low will be the same and 8high will give you extra speed. If your current top is .80 the 13 doesnt have a matching gear so you will need to adjust your driving to accomedate the new trans. Either way it will work. To really answer this, we need to know your current trans model.

 

You most likely have a direct drive transmission. The model number should be on the laminated printout in the dash. For the life of me, I can't remember the exact location. Glovebox maybe. It's been 8 years since I owned a truck with that dash.