What if, hypothetically speaking, you had 2 np435 transmissions and mated them together? If you put them together both facing forward you would have super low gears right? This would be for rockcrawling i guess. Can you turn one of these backwards without having lube or other problems? Like if you mated them butt to butt. The first would turn normal and the second would be turning from the output and the input would get a yoke and connect to a driveshaft. If it even spun in the correct direction could you have super tall gearing and go like 1000mph? I kinda dont know wtf im talking about.

 

if ya wanted lower gearing, just change the gears in the tranny itself. same for higher speeds.

 

Captain Obvious strikes again! I don't think I asked to change the trasnmission gears. Let me post it again so you can read it over.

What if, hypothetically speaking, you had 2 np435 transmissions and mated them together? If you put them together both facing forward you would have super low gears right? This would be for rockcrawling i guess. Can you turn one of these backwards without having lube or other problems? Like if you mated them butt to butt. The first would turn normal and the second would be turning from the output and the input would get a yoke and connect to a driveshaft. If it even spun in the correct direction could you have super tall gearing and go like 1000mph? I kinda dont know wtf im talking about.

 

Ok, well I kinda think you're forgetting a small problem, when you mate transmissions from the output shafts on both, what, and HOW are you going to hook up the other end of the tranny?

 

If someone can fabricate the mounting plates/adapters, yes you can do that. But then you'd have 25 combinations of gears to shift through many combinations being duplicates, and I think that might become rather annoying.

Another option is to install another tranny (ZF maybe? Nice low granny gear, nice overdrive), or install an aftermarket underdrive/overdrive units like Gear Vendors, for example.

Say you have 3.55 gears now, and install the gear venders 30% overdrive unit. You can then install 4.11 gears, put the overdrive unit in 1:1 mode, and have much more acceleration, and if you have a granny gear now, it will be even lower. Then for highway crusing, you can put the GV unit in 1:1.30, and get your regular highway cruising RPM and gas mileage.

 

Now there's a unique idea Sprocket! Mating them would be easy, a short driveshaft like a divorced t-case uses would do the trick and still allow a little movement between them. If they were mounted sturdy enough I'd think a single u-joint or direct shaft would work. The output would take a little machining but wouldn't be too difficult, something to sleeve the shaft and you'd be set. But I think Frederic is right, you'd have a lot of repeating combinations there. Still, it would be fun to try. Or how about just thowing in a divorced transfer case like a 205 but turn it backwards, feed into the rear output and out the input yoke. Then you would effectively double your speed. You most likely would never have enough torque to turn it in 3rd gear on the highway but maybe 2nd gear with the t-case in low?

 

[/QUOTE][QUOTE]single u-joint or direct shaftfabricate the mounting plates/adapters[QUOTE]

Yeah, I thought about the same gear combos. I was just thinking outside the box.

Order of the combo:
tranny belhousing, np435 input, 1stnp435 output to 2nd np435 output using a sleeve, 2nd np435 input with a yoke connecting to a driveshaft. That was the plan. Just a thought

 

A problem with mating two trannies (output to input) would be that you could over torque the rear tranny if they are the same. (ie a Npr 435 with first tranny in first and second in drive could easily have its input torque capacity exceeded.

 

nice. i was kind of wondering that. anyone know the maximum number range off hand?

 

Cool idea. I'm pretty sure this isn't the easiest way to do anything, but I'd like to see it done. Kinda like climbing a mountain . . . Just because it's there.

 

I don't know the actual limits, but I can give you an example.

Let's say the torque limit is 750 lb-ft. That's well above what any of the engines put out, so that's a safe limit for this example.

If your engine is making 500 lb-ft, and your first gear ratio is 3:1, you will have 1500 lb-ft of torque leaving the first trans and heading for the second. Since this is twice the torque that the rear trans is rated for, it will have a very short and violent life.

If your engine only made 250 lb-ft, and most 6 bangers could do that, and you still have a 3:1 first gear, there would be 750 lb-ft leaving the first trans and heading to the second. That's right at the limit of the rear trans.

250 lb-ft is not a very strong engine at all. Also, I don't have the first gear ratio of these transmissions, but I'll bet it's more than 3:1, which makes the real life even worse than this example. Also, I'll bet that these transmissions are really rated in the 500 lb-ft area, not 750 lb-ft.

I'm not saying this couldn't be done, but you need to watch how much torque the boxes can handle, and how much you are sending to the rear trans.

 

Just another example of reviving an old idea in a new era. My Uncle used to build what he called "Grasshoppers". He took a Model A frame and engine, attached the radiator and front cowl with windshield, fitted motorcycle fenders over the front wheels, mounted two three speed (Chevy?)transmissions in series and somehow mounted small tractor tires (like a Farmall A, B or C) on some sort of rear end. I was just a kid when he did it so I'm not too big on specifics but I know he had built quite a few of them over the years.

He fastened a bench seat to the frame ... no doors, seat belts, etc. and believe me it was quite a ride!!!! He had the steering wheel to hang on to and the passenger was pretty much on their own! He had the gears all figured out and would shift between the two trannys. Pretty sure he needed the big reduction for the considerably oversize rear tires.

Uncle Larry was big on hunting, fishing, etc., plus he was a bit of a mechanical wizard. This was his version of a fully capable off road vehicle for the 50's.

 

I think the old logging trucks (big rigs) used this type of set up, two four-speed trannies in line, don't know if they had to deal with the identical ratios, or if the trannies had different internal ratios meant to work together. Another obstacle is how and where to have the two shifters, if there is enough room. And correct me if I'm wrong, but it seems to me that if both trannies were overdrive units, were facing foreward, and both were placed in the overdrive postion, then it would be a much higher overdrive than normal.

 

Most modern trucks don't use what were called duplex transmissions, but it used to be the only way to get more ratios, and more power, out of truck engines for heavy hauling. A well designed transmission set would keep the engine operating in the middle of the powerband all the time.

Later duplex setups usually had a five speed main transmission up front with a three or four speed auxillary behind. The main was usually a straight ratio transmission syncronized in the upper gears, and the auxillary had an underdrive, one or two mid-range gears, and an overdrive ... no synchronizers here. Gears had to be shifted by matching rpms.

Duplex transmissions were very challenging at first but after a while you just knew which gear to grab. I started out with a 5X3 (sometimes called a Brownie setup)which was basically a five speed with a hi-lo two speed, you never used underdrive/creeper/granny gear unless you were "down and gruntin' ".

I graduated to a 5X4 and never wanted to go back. The four-way gave the driver three regular gears to use with the five main gears (15 total), in addition to the granny gear, and was really a spoiler. Lots of gears, a ratio for every purpose, especially if operating a narrow band diesel.

I think it would be a great idea for extreme off-roading or "stump pullin' " but as mentioned earlier you've got to use the right transmissions.

 

I have also entertained similar what-if senerios, trying to use readily available gear boxes (or parts there of) in order to get overdrive. I will offer my two bits worth:

1 Using a transmission that was intended to wear a clutch on its nose posses problems when it is asked to wear a U-joint. Not insurmountable problems, just problems. This combination does tend to be less than ideal.

2 If you can find a 5531 or 5831 Spicer 3 spd auxillary transmission you would have a factory made version of what you describe. They had many versions with different ratios, some had overdrive and some did not. These date back to the '50s and early '60s, only seals and bearings available anymore, but they were tough and not much bigger than a 465 or 435.

3 Doug Nash later U.S. Gear Dual Range is available as either underdrive or overdrive. Functional equivalent to a 2-speed axle, it just bolts to the rear of a transmission instead. This gear box splits 3rd to 4th (and the 1000 r.p.m.) in a sm465 exactly in half.

4 If I were so inclined to manufacture something, I would look to automatic transmissions for sun gear assemblies and related parts, then weld up and machine a housing and begin experimenting. You would at this point be trying to emulate the Dual Range (or Gear Vendors), maybe with a far different ratio, but the same idea.

As I said, I've thought about this kind of project and the Spicer 3-spd and the Dual Range are the best for MY needs. They don't satisfy the need to build something though. Keep thinking outside the box.

Regards
MetalZ