Reversed t-case as "overdrive" unit

[patracy]

This wont work, HAVE to have the slip joints because of frame flex, you bolt everything rigid with the cross members, you WILL BREAK a bunch of something

One could do what I did in my samurai as well. Physically couple the transmission, "overdrive", and t-case together. Then it relies on the flex mounts of the t-case and engine.

 

[patracy]

The frame in the deuce flexes enough that it was necessary to use springs to mount the box! If you leave out the universal joints, you will break something.... At the very least, use an appropriately sized lovejoy coupling.

And after all of that, you will discover what those that drive deuces already know: They barely have enough HP/torque to get up hills in 4th gear, let alone 5th. Add a 2:1 overdrive, and you're sunk if you can't shift it out on the fly.

Also, the gearing in the typical low range of a transfer case is intended for walking speeds. They are horrifically noisy when you try to make them go fast. The deuce is loud enough already.... and you will be driving the gears backwards, to boot... not a recipe for long life.

One of the most unsettling things about using a deuce on the road is traffic lights. I have more than once started when the light turns green, and just about cleared the intersection by the time the light turns red. There is a lot of weight to get moving, and a very small engine... You definitely don't want to toss a 2:1 OD on top of those lower gears!

Give M35Tom the business and buy an OD gear set from him. He'll be thrilled, you will be happier with the ratio, and you will get a well tested product for a reasonable price.

-Chuck

I've never had a problem clearing intersections. I start out in high range 2nd gear followed by 3rd in short order. 1st gear is simply too low unloaded to use. You're right though about the .48 overdrive simply being too much for the deuce.

The OD gearset really is the "fix" to the highway speed issue. But it's just hard to stomach the same cost in parts as you pay for the vehicle. It's way down on my list of things to address. So I'll just keep it in mind for now.

 

[73m819]

the samurai is a VERY short unit, a deuce power train is 3 times longer, also a deuce will have a flex that will break a sumurai
A deuce and samurari are like comparing applies and watermolens

 

[patracy]

the samurai is a VERY short unit, a deuce power train is 3 times longer, also a deuce will have a flex that will break a sumurai
A deuce and samurari are like comparing applies and watermolens

Well my deuce and samurai both burn diesel.

I've had issues in the past with the stock t-case mounts ripping due to torque as well.

 

[73m819]

I've had issues in the past with the stock t-case mounts ripping due to torque as well.

I would guess the mounts were dryrotted to in order to fail like that. even if not, think about ALL the touque mulityplied by all the units.
if this worked, dont you think this would have been done a LONGGGGGGG time ago, to do away with some parts that need MAINTANCE

 

[stumps]

I've never had a problem clearing intersections. I start out in high range 2nd gear followed by 3rd in short order. 1st gear is simply too low unloaded to use. You're right though about the .48 overdrive simply being too much for the deuce.

1st gear is attached to the shaft with a spline. 2nd gear is attached to the shaft with a pair of split pins. It is not designed to take the torque necessary to start a deuce up from a dead stop... even when empty. The deuce operator's manual tells you to always start from 1st. Damage reports shared here on this site have shown ample evidence that the manual is correct.

The OD gearset really is the "fix" to the highway speed issue. But it's just hard to stomach the same cost in parts as you pay for the vehicle. It's way down on my list of things to address. So I'll just keep it in mind for now.

OD is always about highway speed, and top gear. That is why it is unacceptable to have an OD that affects all of the gears, and cannot be disabled while you are in motion.

These trucks are worth a lot more than we pay for them. You would pay $20K for an equivalent truck used (If you could find one!). Another $1K added to a bargain basement price is still a bargain for what you are getting.

I'll make a prediction: In 10 years, if you can find a nice deuce for $20K, you will think you got a bargain.

-Chuck

 

[patracy]

I would guess the mounts were dryrotted to in order to fail like that. even if not, think about ALL the touque mulityplied by all the units.
if this worked, dont you think this would have been done a LONGGGGGGG time ago, to do away with some parts that need MAINTANCE

Wasn't rot. It was the mount design. I had replaced them when I installed the diesel. Since then, I ditched the crummy mounts and used a grade 8 bolt with poly bushings for mounts instead of a design that lends itself to sheering. It was probably ok for a gas engine that made the same horsepower. But doubling the torque is what did it in.

Not really doing away with any parts other than an intermediate shaft on a deuce for something like this. You'd actually be adding maintenance items. But gaining reduced operating RPMs. So it'd end up a wash on the PM stuff. It's still a feasible idea and I know it works in practicality. Just a matter of sourcing an affordable solution now.

 

[patracy]

Replies in bold.

1st gear is attached to the shaft with a spline. 2nd gear is attached to the shaft with a pair of split pins. It is not designed to take the torque necessary to start a deuce up from a dead stop... even when empty. The deuce operator's manual tells you to always start from 1st. Damage reports shared here on this site have shown ample evidence that the manual is correct.
OD is always about highway speed, and top gear. That is why it is unacceptable to have an OD that affects all of the gears, and cannot be disabled while you are in motion.

Wasn't aware of the design, thanks for sharing. Are there any other gears that also share a split pin mounting?

These trucks are worth a lot more than we pay for them. You would pay $20K for an equivalent truck used (If you could find one!). Another $1K added to a bargain basement price is still a bargain for what you are getting.

I can see that point. I wasn't thinking the outward value of it. On the used market, it seems that deuces bring 3-4K typically in running order though.

I'll make a prediction: In 10 years, if you can find a nice deuce for $20K, you will think you got a bargain.

At the rate the economy and inflation is going, I see that to be factual as well. Not so much of the value of the truck. (it'll be a 50+ year old vehicle then) But the fact the dollar will be worthless.

-Chuck

 

[mudguppy]

...
5. the gvw the 205 came in is about 5000bs right? can'the deuce max out at about 22000?
...

no - the NP205 was used through the mid 90's in 1T trucks with GVWRs exceeding 16k lbs, and it was completely under-rated.

same story with the NP203, though it wasn't used past the '80s.

IMO, it's completely incorrect to shun a vehicle part based on ratings and not based on actual value or proven capacity.

example: the Spicer 3053; rated for a 'speculated' 330ft-lbs with a GVWR of 23k+ lbs. first of all, limiting torque to 330ft-lbs to get 23k lbs moving is rediculous. put some more power to it, and it grenades. heck, don't put any more power to it and it can grenade just driving down the road. this trans is horribly designed and is a time bomb waiting to go off. but it has a high GVWR, so it must be sturdy, right?

ratings mean very little when it comes to making modifications. the actual value of design is much more important.


now, to the topic at hand - yes, it can be done and has been done, though not in a deuce. i remember a truck that competed in Top Truck Challenge was running a reversed 203 box - the guy had Unimog 404(?) axles with 7.5-something gears. he ran the 203 box in 'Lo' to give him an overdrive speed on the highway. it was a big Cheby, i think, and i think the guy was from Canada.

anyway, i think it mentioned that it did get a little warm running at high rpms for long periods, so that is something to consider (one of jwaller's points).

however, as it has been pointed out, nothing will fit in the spot that the jackshaft currently resides. you have ~12" from flange to flange. so, you could move the transfer rearward and make it fit - it'll end up needing to slide quite a bit once you get jackshafts for both trans-to-203 and 203-to-transfer.

the jackshaft i just had made is a 1410 yoke shaft to 1410 yoke with a mating flange - it is 8 1/4" from u-joint CL to flange face. when i was at Cline's researching options, we could make one down to a 6 1/2" length, but i can't imagine trying to work with one smaller than what i have now.

so using that as an example, you'd be sliding the transfer rearward almost that full 16". you could do this, but run the risk of the intermediate shaft being too short for the intermediate axle under full droop.

another option would be to make a custom 'hat' to mate the 203 box to either the trans or transfer. this would save you much of the jackshaft length, but may still be 5"+. i'd hang it from the transfer; i wouldn't want another 50lbs hanging off of the transmission.

oh, and these custom jackshafts will be around $400 a piece - you can't avoid this cost because you can only buy parts that are available when it comes to driveshafts of such a short length. there isn't enough room to 'fabricate' something for less money.

what it really comes down to is if you were going to do all that work with relocating the transfer, then i think you'd be better off putting in an FSO or even an RTOO that will give you more gear choices, great ODs, and will be 1,000,000 miles worth of reliability in a deuce.

[on edit: i'd just like to say that if highway speed were that much of a concern and i were putting that many miles on the highway, then i would rather spend $1500 on a freshened Eaton 10spd + the back-breaking effort of sliding the transfer rearward ~12" + ~$500 in drive shaft mods before i spent the money on the 0.69 OD gears for the spicer. reason: all you've done with the gearset is reset the clock on an over-rated tranny. tic-toc, tic-toc...]

but if i were going to do all that, then i'd seriously consider replacing time bomb #2 - the engine.

 

[m-35tom]

sorry, just an all round bad idea. way too much od, the engine just does not have that kind of power. also the od gears work out to $1321 after return of core parts.

tom

 

[Ferroequinologist]

I paid $1450 for the set of G177 11r20 tires for the m109- the OD gears would basically be the same kind of investment. Worth it in my mind.

 

[Trango]

If you are going to stick any sort of ancillary gearbox into an otherwise stock powertrain, here's what you want to do - bob the truck, and put a brownie box in between the aft end of the transfer and your single rear axle.

Seriously, if you want a steeper OD, tom's new 5th gear cluster isn't that bad of a price. Me, I needed more splits for highways in the mountains, but I'm always building vehicles with visions of a silk purse.

Best
Bob

 

[patracy]

Honestly, running through all the numbers on stuff. If the engine fails I'm just going to swap in a 12 valve cummins. I can swing that for the cost of the OD gears on their own. The cummins (with valve springs and pump mods) can spin 3K rpm all day no problem.

Once I get my adrenaline unit modified I'll be spinning my cummins up to 4K or beyond. (I've already put 110lb springs in it)

For $1500 you can score a cummins engine from a pickup truck. Then just source a SAE flywheel and adapter plate.

 

[tm america]

If you are going to stick any sort of ancillary gearbox into an otherwise stock powertrain, here's what you want to do - bob the truck, and put a brownie box in between the aft end of the transfer and your single rear axle.

I don't see how bobbing the truck has anything to do with or help you in anyway with what the op is talking about....bobbing a truck doesnt give you any more room between the transfer case and rear axle for an od unit of any kind.nor does it effect the top speed or running rpm....There are plenty of threads about bobbing trucks this is not one of them this one is about adding another od gear...further more if you put the od unit behind the rear axle you could only use it when not in awd or it would destoy the drivetrain...

 

[Oscarsbigredball]

Yes, that's exactly what I'm talking about. The NP205 and the NP203 gearbox have a 1.98:1 reduction range.



You could place it afterwards, but there's a few things to consider. You can't have it in 6x6. Sprague trucks can't run it. And the effective torque load would be doubled to that "light duty" t-case when the rockwell t-case is in low.

But with the np203 right after the tranny you would be doubeling the rockwell t-case rpm meaning effectivley more wear. And numero dos, when do you plan on needing 6x6 at 65 mph

 

[Welder Sam]

Ok. My curiosity has gotten me.

What engine would u put in front of the Eaton 10speed that would maintain 10-12mpg w/o sagging the front springs?

 

[robert c neth]

we run 2 t cases in our mud trucks because the tires are 62" tall usually the 208 and they hold up well .usually break the tranny ,so a cast iron case should be stronger.have you thought of bigger tires for od ?.that mod is a lot of work and if you ever sell the truck i doubt it will increase the value.good luck either way.