Also, double OD is practically useless, especially with an E40D with a ZF it puts your cruise speed below the powerband.

 

an aux unit behind a E40D/Zf-5 trans doesn't make sense to me either.unless the truck is a F-super duty/f-450 with the 4.63/5.13 gearing.in that case you could use double od when empty at least to save on some fuel between loads.

side note;
after this post i decided while i had the time,i'll call about a gear swap for log truck.5.13 to 4.30 gear swap.quoted $2,100 .......ouch.i don't think so.can just buy a used latter '99+ rear axle for half the price w/4:30 gears already plus e-brake shoes so i could swap in a bw-1356 t-case and have a brake for inspections.

 

it would be beneficial for the under drive and the over drive in heavier truck though wouldnt it?

 

With an automatic not really, because with the TC locking and unlocking you pretty much have 7 gears anyway. Regardless with a rig that already has OD, 4.10 or otherwise, its really not worth the cost. Taller tires would be a good way to gain some ratio. 255/85s are a nice narrow profile that are around 33-34" tall.

My honest suggestion is keep your eye out for a wrecked 86-97 F250/350 and keep your fingers crossed for 3.55s and/or someone looking to swap 3.55s for 4.10s. Unfortunately its seems that owners of used pickups always want the gears they dont have... For instance i also want 3.73 or 3.55 and most people i know with 3.55s want 4.10s... go figure. Even worse the pair of axle i picked up were originally 3.73 (ideal) however the pinion bearing went out of the rear and ate the shaft so he had it rebuilt... to 4.10. Not a big deal i thought. Well in a sterling its a pretty big deal. Unlike my Dana 50 which just requires some patience and $40 Worst of all, i cant decide what to do. Regear the front to 4.10 with my old gearset for $40 and just deal with it, or re-re-gear the rear to 3.73. Im hoping to use this oportunity to convince myself to get a locker which would require setting up the rear-end again, so at that point the gearset would be the cheap part lol