Stick with the 10 speed or go to a 13 speed?

It depends on your 10 speed if its an eaton look for the serial tag if it just says RT that means its a direct or 1.0 final ratio. If its RTO that means its over drive but probably a .84 or .80 final ratio if its rtx that means is a .73 final ratio. the later low inertia 13 speeds are .73 final ratio the older rto 13 were .87 final ratio. For the most part transmissions use the same final ratios but more gears means a closer spread in between the gears. Unless your 10 speed is a direct going to a 13 isn't gonna be much help

 

I would be checking with a trucking auto wrecker, they will know what ratios are in the box, I used 99 truck parts in B.C. They were always a gold mine of information, and parts. I worked with some of the best gear persons around so I was very lucky. You will also need the driveshaft from the transmission to the steady bearing most times.

 

The difference between a rtx,and a rto is the rtx has a 4 rail shift cap & the rto only has a three rail! They have the same overdrive!

 

Sorry there ol buddy didn't have my ratio chart right in front of me and couldn't remember if the 10 and 15 were the same also the RTO and RTLO trans are different ratios. The RTO 15 are around .80 or .84 need to check with a tranny shop to be sure. The RTLO 15 I'm thinking are .73 final ratio again I need to either get my book out and look or check with a sure enough gear man. The difference in 3 rail and 4 rail trans is the 4 rail top is to turn what would be a reverse pattern to a standard pattern. I don't like to give bad info and the probably I put in that post means I'm not a hundred percent sure. Thanks for clearing that up

 

Lol! It's a lot of info to remember!!! A 15 over is a .79 overdrive!!! Yours has what I call a true double over! .62

 

That's right .79 I can't ever remember that. Why the .80 sticks in my noggin I can't say. Yeah she is the true double over .62 for some reason I can remember my stuff. lol I guess its true you don't use it you lose it.

 

My brain is full of useless information!!

 

That's not useless BOTH y'all keep it coming I'm soaking this up lol. By any chance do you remember the ratios of an old 2 stick with a 6 speed main and a 4spd od brownie? I kept thinking the OD was a .64 when all was said and done but can't remember for sure.

Oh BTW as for the OP. All you will gain is the ability to split gears and only take half a gear on the grades and hills instead of a full gear. With 3.90s put back unless you're running a very low horse power motor I doubt they'dput a direct drove 10spd in that rig. Seems like fuel milage would suffer to greatly but I'd pull really well.

 

I think I know some one to ask, but he is a cranky old fart gotta take a half of case of Old Milwaukee over there and have a couple with him to get his trucker stories fired up. Man that stuff is rough even worse when its cowboy cool. He wont touch it cold.