How to identify if a transmission is double OD

The vast majority(if not All) of 18 Speed Roadrangers are Double overdrive....

https://www.eaton.com/content/dam/e...eed-transmissions-brochure-trsl0250-en-us.pdf

 

Have to agree with you here.

 

You can purchase to-date a 13/18 with direct 1:1 final ratio.

 

Someone else would have to do the math. Dad ran a BC3, then a 444 2450rpm, 12513 and 4.11s on lp24.5s. 89 mph was max. Up hill, down hill, or sideways.

Trucks in the last 25 years are way faster.

 

Had a 15 up against the dash in the 80s, it had 3.70 rears. At 1900 rpm it was 115 mph. Maybe the OPs rear end ratio has been changed, with 4.25 it would be hard to hit triple digits

 

Down Here In Australia I've never seen (or heard) Of a Direct drive 18speed. !!
They're all double overdrive so you can run deeper Final drive ratios to improve startability at out High B double & road Train Gross Weights..

 

I'am not calling you a liar.. I was only pointing out that it would be pretty tough to reach the triples on 4:25s
only saying that from experience
I meant no personal offense to you