13spd vs 15spd transmission?

Kind of... I had one for 10 years. The one with high gear up by the dash , oldschool....

With a heavy load I’d go 1st 2nd 3rd 4th all on the low split side and back to 3rd in regular low then 4th then on the high side...

the splitters locked each other out so you couldn’t screw up too badly....

 

That's a 15 over.
All I'm saying is there are no splitters just range selectors. 15s have a blue range selector on the shifter head as I recall.

 

15 speeds DO NOT SPLIT!!!!!

Its an extra set of 5 gears in the basement called deep reduction.

You won't gain anything by going to a 15 speed. Many 15 speeds use the exact same main box as the 10 speed. Only difference being the 15 has a 3 speed aux box vs a 2 speed aux in the 10 speed.

 

I was doing some fiddling with gearing on a new Cascadia.
The 15 speed would basically give you an effective gearing similar to a Detroit DT-12 AMT transmission, with a slightly lower deep first gear. A 13 speed would be more drive able.
If you're going to spend the money an 18 would give you the best of all worlds.

 

Wow. Should be closer to $7,000 all in with a brand new off the shelf trans.

you need a new shop!!

 

Go to a salvage yard and buy a core transmission cheap to get rebuilt.

 

Have you tried truck salvage parts yards? Lots of great parts to be found on insurance totaled trucks.
Some places will even trade. I know places have traded rear gear differential sets and transmissions for years. Shipping from another part of the country can be an expense but if you are able to drive there and pick it up you can get off cheaper.

An oldtimer friend of my grandfather drove 300 miles and back in the late ‘70’s in a ‘66 vw beetle with a blown complete Rockwell sq100 front drive differential, axles , and housing tied to the roof to trade off of a freshly wrecked truck up in Amarillo. Lol!
Gotta do whatcha gotta do. Sometimes.