Rear End Gear Ratio

That’s more or less where my truck runs and I have a 13 with low pro 22.5 and 4.33 rears. BTW in most 13 speeds 11th is direct, not 12th.

 

I think we discovered in another thread the original 13 speed went tits up. So it was replaced with a RTO15613 which ends in .87 or an easy way to say it a half hole short from what everyone today is used to.

 

Yeah that's where he's getting burned on the top end. .73 final drive gives it the legs it needs.

 

I thought over drive was stronger than direct???????????

 

1700 sounds about right. Plug these numbers in the calculator.

40 in tire
3.55
.87
1700 rpm

Transmission Ratio RPM Calculator | Spicer Parts

 

Is 13 speed with 4.33 a heavy haul spec? Currently looking at a 12.7 DD with that rear end for OTR work, max 80K gross(usually bt 75 to 80K). Looking to cruise at 65mph. Drive mostly in flat lands

 

I feel left out, why no 370 ?

 

I know this is an old thread,but yes,they used to make a 13 speed direct,haven't seen one in a long time. Had one in my 1969 IH COF4070A. NTC 335 Cummins,13 speed direct,4.11s,tall 10:00-22 rubber. When you came out of the low side,you split under the gears,instead of over. 13 direct was high gear.
Was a very good running truck,in its day.

 

HH not by a darn site. Truck has a M11 and it needs a 4.33:1 rear

 

I haven't actually located that? I do happen to have lousy online search skills, so its probably a me thing. I did see something google referenced, but I could not find on the site, something as called "T680 Online Truck Configurator"