I have an older 2wd F-150 (see my signature) which has been very good to me for nearly 300,000 miles. I have 3.73 gears and no overdrive. It never was a problem until I moved to Milford DE. Now everywhere I go is a highway ride away, and 2600 RPM at 60 MPH is a pain in the gas. I love my NP-435, but even when I pull an 8,000 lb trailer, I do not need low gear. I found a wrecked F-150 at the junkyard with a fresh M5OD. It's got a transfer case attached to it. I want to keep the case, remove the front drive chain and use it as a reduction gear to cure the M5OD's most annoying habit of requiring excess clutch slippage when backing up with a load. Also, If I need some extra gear for a heavy load, the transfer case low range and M5OD's 1st gear are still lower than the NP-435s low gear. My question is, can the transfer case shift between low and high range just by depressing the clutch pedal and pulling the lever, or do I need to stop first?

 

Also posted in the six forum:

https://www.ford-trucks.com/forums/9...ction-box.html


Two words: Zeee Efff.

 

How hard is it to convert an NP-435 to a 4WD output shaft? I really love this box, and I think I have a better solution. Instead of the M5OD, I'll just grab the BW transfer case, and install 2.73 gears in the rear. That way, I can keep the NP-435, and have an ultra low reverse for when I am backing up, and an ultra low 1st gear for pulling a parade float (I am a teacher, and use my truck for the homecoming parade), a 49.2:1 1st gear ratio and a 59.1:1 reverse ratio in low range, and an 1,800 rpm cruise rpm at 60 MPH. I think this is my best solution.

 

For the work and all that is involved, I think you might just want to throw in the 5 speed and transfer case. Did you put the NP435 in there? An NP 435 is not hard at all to tear down, BUT I think you will not like having the 2.73 gears for in town use.

OR go with the ZF.

 

I originally had 3.08 gears with the NP-435 and I had killer mileage under 65 MPH (I could pull an average 21.3 MPG with a steady foot and a close eye on the speedometer) and it pulled the 8K trailer no problem (I still rarely needed low gear). The problem is that the differential gave up at 230,000 and I did not have facilities to repair it, so I just had to swap the axle with a 3.73 unit I got at the junkyard. The only thing I didn't like was that the 3.08 gears still had me going too fast in reverse when backing a trailer in tight quarters, so I had to ride the clutch. I admit that this is one nice thing (the only nice thing) I have to say about the 3.73 gears; backing trailers in tight spots is easier on the clutch. They dropped my overall mileage to 13.2 MPG, with a highway average of 15.8, and no capability of going faster than 65 without screaming the engine. I rarely exceed the posted limits because fuel is expensive, but when my grandfather was dying a year ago and I got a call from my father saying get here fast, I drove from Woodside DE to Springfield PA at 85 MPH, and the tach hovering on 3,800. That was for over 100 miles. I didn't like that experience. FYI My mileage for that tankload was only 9.4 MPG. Given that this was an unusual occurrence, this incident is not part of my MPG average with this axle, or it would be even worse. The M5OD would give me an effective 2.93:1 ratio when it's overdrive is multiplied be the 3.73 ratio. 2.73 gears, on the other hand, along with the NP-435, would give me an even better overall cruising ratio, but then I have that "fast" reverse problem even moreso than when I has 3.08 gears. Thus the transfer case for gear reduction. Also, when trying to pull a float at 1.5 MPH, I'd still have to slip the clutch with the NP-435's low gear with 2.73/3.08 gears, but I could easily do it with the NP-435's lo gear and the 2.62 ratio of the transfer case lo range. 2.73x2.62= 7.15:1 final drive. With the NP-435 6.88:1 lo gear, I end up with an ultra low 49.2:1 compound lo ratio, perfect for creeping in a parade without slipping the clutch... or pulling a house off it's foundation at idle. With 2.73 gears. I think I have found my solution... I love math.