2 speed rears/ auxiliary box

Some of the heavy haul guys I know run 2 speed rears and a couple running a second box air shift

 

Years back trucks didn't have the torque they do now .. Unless your going to a expensive heavy haul type of two speed I wouldn't think that most would hold up to the torque .. Interesting idea though a 18 speed/ 2.64 combo like cowpie has would probably be the closest you would find

 

IIRC, "Wore Out" put a new 1750 Spicer with an air shift (single stick) in his 359. Another fella....("Jake the Bullhauler" maybe?) was running the old style aux trans in his 359 but I think he had reliability problems last I heard.

Geez how fast do you want to go? I am still .78 15OD with a 3.90 rear on 24LP. Yeah it sucks I know.

 

Auxiliary box would give you lower and higher gears if you go with a 3-4 spd setup. 2 spd setup only gains you on one side if my memory is right. Plus... Twin sticks are always cool, IMO.

 

I think they're up to the task.

 

That isn't engine torque, but rather the torque being applied to the input shaft of the aux trans. If the engine is rated at 1700 ft lbs, and your low gear is 13:1, the aux trans input torque is 22,100 ft lbs. In other words, you couldn't use low gear on the main transmission without exceeding the rating of the aux trans.

 

I run a heathy 3406B never had it on a dyno but she's stout. I ran a RTOO 14613 for years till I build what I have and the OO wouldn't survive. I run a 18913 and a 1750 spicer 4 speed now. Right at a 100k since the swap not had a bit of trouble. I did pull the 1 and 2 gear out put dummy spacers in there place. All I use is direct and over. When they are both in the big hole with 3.55 and tall rubber she will roll for sure

 

How fast do you want to run? I drive a W900 with factory ISX 500/1650. Has 13 speed, 3:55 rears ( I believe), and 24.5 rubber. At 90 mph I'm turning 1800 rpm. It will turn 2200 rpm, I figure that should be around 110 mph. Never had it there, 90 is fast enough for me.

 

From what I read, you want more speed or less rpm or both. 2 spd rears and 2 spd aux boxes give lower gears for pulling. A 4 spd aux box will get you 2 o/d but the weight, price, and installation may not be the best option. With your setup, if you have the power, different rear end gears ie...3.36,2.84.....google "big rig road speed calculator" and play with some numbers and see what you might be able to get away with.