15 speed double OD

That is correct, there will never be a double over 10 or 15 speed.

The transmissions that brought about the terminology were 13 speeds that had an over drive main box as well as an overdrive auxiliary, hence double over.

Those transmissions actually have 3 OD ratios.

A modern RTLO 13/18 is not a double over, they have an overdrive main box with an under drive auxiliary.

 

A 15spd double overdrive does exist but you cant get it from a factory. Theres a few transmission shops that will still actually do it. They have to do some gear flipping and rearranging but it can be done i know for a fact.

SmokinCat is smokin crack. RTLO 13 & 18 spds are most definitely double overdrive. I dont ghink he truly understands what double overdrive means. Cant remember the exact last 2 ratios but i believe they are .89 and .72....rtlo13 11th is 1:1 and rtlo18 16th is 1:1.... anything is possible with the right tools and knowledge just dont expect to find a part number for it or siiting on the shelf at your local part store.

 

I started driving in 1972 and never ever heard the mention of a 15 double O, until now.
Heard of RTOO 13's, double O 5X4's, but never a 15 double O, I suspect because there is no such thing.
If there were such a thing, and if it was a good thing, more truckers would have modded them.
That's why there weren't a lot of RTOO 13's, they weren't that good.

Sureshot3333 and SmokinCAT
OD ratios on modern 13's and 18's are .81 and .73.

7 Hi is 1:1

 

I understand your desire to right but your wrong snow monster. Double O/D 15s do exist but by modification only. Ill contact my transmission guy to get some photos as proof. .....llike I said, my ratio numbers were from memory and i wasnt sure exactly. Your numbers are wrong as well. Maybe next time you try and correct someone you should have more knowledge about the topic than simply driving since 1972. Driving a truck doesnt make your opinions fact. I attached some "facts" from eaton.

 

RTOO 13 transmissions are triple O/D not double. JLYK

 

And they were solid transmissions but most engines didnt have the power to make the .62 final ratio useful

 

7 Hi = 16th

 

Smokin cat is right. He’s talking about the old 13s. The ones they called double over had the .87 .73 and .62 overdrive ratios. Yes you can make other things into whatever. Modern 13s have .87 and .73 overdrive ratios. Not going to explain to you about the fact they are really underdrives.