2wd Underdrive Unit Options

[MountainBikeRoamer]

Having to modify the fuel tank to make room for the transfer case:
Do not like

This tank modification also ends up surrendering some of the fuel-tank's total capacity, too....does it not?

The range on one fuel tank is already short enough as it is....what with ol' Thirsty's big 10-11mpg appetite for the dino-juice. Hate to give up some of that range in exchange for the occasional need for a low climbing gear.

[TeleSteve]

Would a passenger drop transfer case work without tank modifications?

[Bbasso]

A shortened fuel tank looses aprox 3-5 gallons fyi.
Or get the full replacement which holds 35 gallons and fits the 271, that I mentioned earlier .

[JackTuppVan]

I am posting this for additional reading on the subject of planetary over/under drive units.

I'm not suggesting this as a possible solution.

The HONE-O-DRIVE is and axle mounted planetary over drive.

I actually had a hone-o-drive unit in a 1970 cougar years ago , if I had only know how rare / expensive it was I would have kept it .

Apparently they are reproducing them.

it works on the same principal as carringb describes.

Originally Posted by carringb

That all said... One workaround for a lack of off-the-shelf under-drives, is to go ahead with the Overdrive, combined with much lower gears. You'll get lower overall ratio needed for off-road driving, but still retain a reasonable top final-driving ratio for highway cruising.

http://hone-o-
drive.com/hone-o-drive/

[TomsBeast]

For a little more fun reading on the subject:

Here's a machinist that built his own doubler box, a "Klune-clone" using a planetary gearset scrounged from a New Process 231 transfer gearcase. This one bolts between his automatic transmission and his transfer gearcase. Great pics.

homemade Klune v style doubler - Pirate4x4.Com : 4x4 and Off-Road Forum