I'm curious about a Meritor application guide.

I had a DP404 40,000 lbs rear, I think the input torque on that was around 18,000 ft-lbs. An 18 spd on my MBE4000 could deliver 23,300 ft-lbs in bow low first gear at full power. Which I did once coming out of a farm yard in freshly turned soil climbing the access to the dirt road. The bearings in the front diff gave out shortly after that episode.
Yes the formula to calculate max input torque is full engine torque x lowest possible first gear ratio. So my DD16 at 1,850 ft-lbs and a 14.40 ratio low first gear would send 26,640 ft-lbs to the front diff input. So I couldn’t even use that axle with its fastest ratio of 2.80
I have RT46-160 so I could go as slow as almost a 5.38, I have a 3.91 which the axle is rated for 30,000 lbs. So I’m good to go.

 

The main reason I overloaded the axle on the older truck. It was spec’d for 80,000 lbs work and had a 3.58 rear ratio.
I got the bright idea to switch over to pulling super b-trains, 140,000 lbs gross. So I changed the rears to 4.11 ratio, at the time I remember reading that guide and knew I could be overloading the input torque. But application at the time was all highway work, so on pavement I never had the need to use full power in the lowest gears.
Later I changed to pulling the same weights with super b-train hopper bottoms, now I was loading in farm yards and out in fields. Much tougher work environment.

 

ECM programming now a days

 

Interesting.