Can anyone explain to me how a two speed rearend works, and can one be used on a ford pickup?

 

Most use a 2-speed planetary-gear 'transmission' attatched to the third member of the front axle in a tandem axle setup, used on big rigs. They can be found in single rear axle trucks too. Most are air shifted, so a compressor system would be needed. If your truck is 4x4, the extra low gear would be useless when in 4wd unless you had the same 2speed axle in the front as well. Most of these axles have very low gearing and wouldn't really be suited to a pickup truck. They are also very heavy compared to a pickup axle and most have air brakes on them and 10-hole wheel lug pattern and need large diameter commercial truck wheels (22-24") to fit over the brake drums as well as being very wide, as the trucks they come in have duals in the rear. The second gear is typically a very low gear, like a granny gear in a 4speed transmission. Notice I say 'typically' and 'most', so who knows, there may be a 2speed rear out there somewhere that is small enough with the right gearing and hydraulic brakes and small enough drums to use in a pickup...

If it's an overdrive gear you're after, look into swapping to an overdrive transmission, like an AOD auto or ZF 5speed. If it's a granny gear you're after, look into swapping to an NP435 or T18 4speed or ZF 5speed.

There are also companies such as Gear Vendors and US Gear who make auxilliary transmissions for pickups that go on the end of your stock trans and give you either one gear over or one gear under your existing gears. Check them out at www.gearvendors.com (overdrive only) and www.usgear.com (choice of overdrive or underdrive models).

 

Thanks alot that all I needed to know.

 

I disagree with 'most' of what SoCalDesertRider has posted. They are found in mostly single axle trucks and are electric shifted not air. True they are bigger and heavier than those in a pick-up truck but then that is the reason that the brakes are also bigger. And the brakes don't have to be air either. I driven more than my share of 2sp rear axles and only one, a single axle International tractor, had air brakes or any type of air system. The axle on this truck was electric shift. All others had hydraulic brakes. All othe the trucks also had underdrive axles.

 

Waited too long to edit last post but here's the Dana Axle website and 2sp axle pdf.