History-I've never opened up an alumin case, chain-drive transfer case. The most experience I have is opening up and looking inside a Jeep Dana 20...didn't even touch anything. So I could be full of **** for all I know.
I've seen Dana 20, Dana 300, and NP203 Gear driven transfer cases with aftermarket low-range kits. I think I've also seen an aftermarket low-range kit for a NV231 (?) aluminum case, chain drive unit.
Now...if manufactures can produce lower ranges, can't they also produce higher ranges? Seems logical to me...just a gear right?
This is what I'm after. I'm actually looking to theoretically cut off the front output from a BW1345 or BW1356, bolt/weld a cover over the cut off area, and use the unit as a gear reduction unit in my 2wd F350...it'll really help when starting with a load. Then i would buy either a Ranger Torque Splitter from Advanced Adapters or some other type of gear splitter (Gear Vendors, U.S. Gear, etc.)
But, I got to thinking...since manufacturers do offer low range kits, they should also be able to offer a gear kit with "splitter-friendly" gears, and a synchro setup of some sort. The stock ratio in low is 2.6:1, if they offered a 1.3:1 ratio gear, that'd act as an underdrive and allow the operator to split gears. HOWEVER, it would only work if they was a way to shift into low range while moving. I believe with a taller gear set, it should help, in theory it's easier to shift into 3rd or 2nd than it is to shift into 1st in the transmission... The better option would be for them to have a .73 overdrive type gear. The operator could split gears and gain an overdrive. That would allow for the install of a HD cast-iron 4 sp (NP435, T18, T19)
To get away from the towing/hauling aspect, this gear set would allow consumers to purchase a used transfer case, cut the front output off, bolt on a cover, and install the gears - gaining a stout, short, useable, secondary gear box. With factory parts-adapter and linakge-the gear box could be repaired with factory parts. The box could be used in front of a "doubler" setup too for those into hardcore 4-wheelin'. It wouldn't be 6.76 with both in low (which is how the math works for 2 BW1356's in low), but if the splitter box was OD, your low range would be 1.9 (2.6 x .73) for the situations that don't require so much gear down. If the splitter was UD, you would get a 3.38:1 ratio (2.6 x 1.3). Those aren't really as low as a wheeler would like. BUT, keep in mind that if the rig was diesel powered, the user could install a wide-ratio NP435, T18, or T19. With the short RPM-range of a diesel, the wide ratio gear box would offer good driveability because you could split every gear with the splitter. The killer low 1st gear would help with what you lost with the "doubler" box acting as a splitter.
So, if the splitter was in direct (1:1) while wheelin', the NP435's crawler 1st of 6.8ish times the 2.6 low of the t-case would give 17.68 going into the axles. If the splitter was an underdrive- 6.8 x 1.3 x 2.6 = 22.9ish going into the axles.
Well...could be just crazy talk, but it could also be something do-able...any thoughts?
I'd like to have a unit like this using factory parts (minus the gears), to gain a splitter for driving my 2wd rig. I realize I could just buy a Ranger Torque Splitter, or a Gear Vendors unit. But they run about $1,500 for the Ranger and $3k for the Gear Vendors unit. They are both only rated at 25k GVW. That's probably enough since manufacturer ratings are on the low side for liability, but it seems like these transfer cases hold up well with guys having killer big blocks and souped-up Power Strokes...the transfer case input is ALREADY increased dramatically after the transmission reduction. So, i think these units can handle more than an aftermarket splitter. Not to mention-the GV doesn't split under 20 mph, and doesn't do well in reverse. The Ranger splitter requires transmission bearing retainer and input shaft cutting. So-in comparison, the transfer case looks a lot better to me, anybody agree?

 

the only problem is getting a synchro working right, and the cost of such a set up. it would be cheaper to go with a splitter thats already available (us gear is personal favorite)

another option is to find an old brownie aux transmission. (ever hear of a twin stick in a semi?) the one my dad has is a 2 speed (2:1 and 1:1) but they can be found in 3 and 4 speeds as well, but be prepared to learn how to drive again.

 

I recently bought a 1973 F-250 HD 4x4 with a NP 205 TC and a T-18 manual 4 speed. In a nutshell I had a 1976 F-250 for 20 years, made a stupid choice to sell the truck to try to save a failing marraige and have just now healed the last divorce wound by once again reacquiring some old Ford iron. Also re-married to a girl who likes old Ford trucks so that problem is SOLVED.

I have been pondering this very question--why hasn't anyone, at least to my knowledge, made a gear augmentaion kit for the NP 205 transfer case's high range to create a 27% overdrive or perhaps a transfercase PTO overdrive like I had on my old CJ2A Dana Spicer 18 TC? I'm not sold on the NV 4500 conversions and I'm not keen on the Ranger OD and the drivetrain modificaions it requires. It also appears as though the GV unit has a spotty track record and is very expensive.

Given the rising costs of fuel it makes sense--at least to a non engineer like myself--that by regearing the NP 205 TC's high range that one could keep the advantages of the tall low range of the T-18 granny wide range trans/TC combo and, by regearing the TC's high range, the T-18 would become a true usable 4-speed and these trucks could cruise at highway speeds without altering driveshaft length, moving gearboxes, etc.

Thoughts, ideas or ?

Thanks for your patience.

 

That's probably a good idea. Would you buy such a kit for $1800? $600?

How many would they sell?

 

None of these options would be cheap--GV is over 3 grand just for the unit, Ranger is at least 1500 for the unit plus all the fabrication that has to be done, U.S. Gear's dual range aux trans is also in excess of 2500 plus it looks like it is almost a little automatic trans. All of these also involve installation costs as well so add a grand to everything if you don't have a shop. I don't have the shop or knowledge of old auxilliary units to find a used "brownie" and install it. So I'd pay 1000-2000 for something that would work with my stock drive shafts and keep my gear boxes in the same place. It would be worth it to me because I ain't ever selling this truck.

I've never done any TC work so be patient...

I've since discovered that STaKS exprimented briefly with this around 2005 in their custom Monster Box cases but that option is no longer available.

If there are any gearheads or transfer case experts out there who can enlighten me I'd sure appreciate it.

 

muscletruck - What if there were no synchro's, and I "self-synchro'd"? I wd have to do that to drive a "crash-box brownie" at's non-synchro anyways. I hear you on the browne box though! I've spent about 20 hours reading and gathering information on the different Spicer models. I created Word and Excel documents and everything. Unfortunately, the hard drive on that computer blew and ALL my friggin' truck files are gone!
YouTube - Twin Stick Shifting
The part I don't like about the brownie box is having that small driveshaft between the trans and brownie box. My goal is for a married unit.

kindofrotten - Sounds good to me.
With a T18, you've got 6.3, 3.1, 1.7, 1:1 Direct, 7.4 Reverse in stock form.
IN .73 OD you've got 4.6, 2.3, 1.2, .73 Final, and 5.4 Reverse. The problem is that you may slip the clut excessively starting in second gear sine first is non-synchro and you gotta be pretty much stopped to shift in to gear. You could find a T19 from a 460 4x4 F250. Same gears, but 1st gear is snychronized...Just a thought.
That STaK option sounds REALLY nice, I wonder if they lacked enough demand...
I actually e-mailed back and forth with Advance Adapters asking if they would re-gear the original planetary gear set in their 4 speed box. The salesman said they have done a lot of work and experimenting with that option. He said that transfer case wouldn't hold up behind a turbo diesel, so I never asked if they would offer that someday.
US Gear no longer builds their auxiliary UD or OD units anymore.
The Ranger unit can only handle 450 ft. lbs of torque, so it will not survive behind a turbo diesel. It also requires some transmission modifications, driveshaft shortening/lengthening, and floorpan cutting/welding.
The Gear Vendors seems to be a favorite among diesel owners who tow. Unfortunately, this unit has drawbacks. They have some plastic parts inside the guy were chatting about on some other forum. They don't hold up well in reverse when backing up a load. And they also are limited by design, relying on fluid pressure to shift. This limits them to be somewhat like an automatic transmission, and they can't split under 20 mph.
I've since drawn out 2 plans, both similar. The first was a typical NP203/NP205 Doubler. Maybe some machine shop could re-gear the NP203 to have a .73 OD and a 1:1 Direct for gears. The NP205 would still have low range.
The second option was similar, using a BW1345 or BW1356 as the first reduction box and being re-geared to .73 and 1:1 also. The transfer case would be either a BW1356 or a NP205.
I imagine your idea is possible. I imagine you would just need gears manufactured by a machine shop. I don't have any internal experience, just going by common knowledge of how gears work by reduction.

 

Thanks for the quick replies, we're all kind of making this up as we go along so I appreciate any and all info. Here is what I have found out since my last post:

Land Rover owners have two options--either they can buy a Rover's North "high ratio" transfer case that has less than a 1-1 final ratio. Alternatively, Ashcroft also offers a high ratio transfer case conversion--both are UK companies. These are not true overdrives because they involve regearing the high range and thus are always engaged--exactly what I'd like to to do with my NP 205. Additionally, LR owners also have the option of a true bolt-on overdrive unit.

There are also aftermarket high range regearing options for Suzuki, Toyota, and even the old Jeep quadratrac transfer cases that result in final ratios of less than 1-1. Of course then there is the Dana Spicer 18 OD I mentioned in my first post, and there is also an OD for the Dana 20 as well.

Even saw where someone was running a Ford 302 in a Land Rover and had it mated to a driveline that included one of the high ratio transfer caes. I'd like a peek under THAT truck!

The word on the STaK is that the OD was not intended to be run very much, just to and from offroad, so it was not a good option for extended high way use. The STaK box had a 1-1 high range and was intended to be run in that configuration on the road.

So it appears as though if this idea is viable it would have to involve a TC awhere the high ratio would have to be altered to say 1-.73 and it woudl always be engaged except for times when the driver elected to use low range which would retain its original configuration or close to it depending upon modifications to the input assembly. The new high range would essentially make the stock T-18 gears taller and allow one to use granny as first--I've shifted T-18s from granny to first plenty of times without problems or grinding--patience and doubleclutching are the key. Of course the T-19 would work well with its syncronised first gear.

I've written a few gear manufacturers and will let you know what I hear.

Anyone else have any ideas about this? Thanks!

 

Wow, I did touch on some of the Land Rover info. on my searches a few months ago. Didn't realize just how good they had it!
When I was in contact with Advance Adapters, the salesman said they couldn't produce a unit strong enough to handle a Turbo Diesel. So I'm not sure if it could handle Full-Size Truck duties. The salesman said a diesel truck can pull a loaded trailer, where a Jeep will just hop and not have enough weight/traction to move it. Maybe the unit can handle duties behind a gas V8? The 4 speed unit would be excellent. The first reduction box would be .73 and 1:1, the transfer case section would be 2.6 and 3.8.
If the Land Rover crowd has those gears available, then the concept must be the same for a NP205.