# Gear reduction



## glaurung (Nov 11, 2009)

Hi, looks like a hi-lo transfer box that is needed when driving in rough conditions. Most 4x4 vehicles have that allready. This is just built for hard use, might be overkill for your purpose. I do not know how tough original is but off roaders can answer that.
It will whine like hell on 11 000rpms, my kostov has limit on 5800 and makes quite a sound allready on my Range Rover.
Regards, Harri


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## dragonsgate (May 19, 2012)

Jan said:


> I've just ordered the siemens azure combo. And am researching gear reduction. My donorcar is a Landcruiser BJ40. That's a FJ40 with a diesel engine.
> 
> I've discovered the world of crawlers. But the english jargon is making me a bit insane. Do I understand correctly that marlin's toybox is an option for me?
> 
> ...


Hi Jan, Before you spend money on reduction gears I would suggest putting lock outs on the axles. If your Toy is anything like mine was if you get the axles cocked you aren’t going anywhere no matter what gear you are in. What is the gear ratio of the third members? If it is 4:11 then that with low range will enable you get stuck in some really inaccessible places.


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## DanGT86 (Jan 1, 2011)

That is one way to get the gear reduction needed to turn 10k rpm into useable driveshaft speed. Most offroad transfer cases with big gear reductions are not used at high road speed. You would be spinning lots of weight and bearings really fast for no reason creating a lot of heat and wear on parts. 

That being said, marlin is the first person I would ask when it comes to toyota driveline stuff. Marlin carries the gearsets needed to get 4.7:1 gear reduction in most toyota transfer cases. Its cheaper to change the gears then to buy a whole new case. It also looks like the toy box is for adapting 2 transfer cases to one vehicle. By doing that you can run either case on or off or both at the same time which multiplies the first reduction by the second creating super low gears ratios. 

If it were me I would try to get the gear reduction before the input of the transmission with a belt or chain drive. That way the transmission is operating in the rpm ranges it was designed for. There arent many ICE transmissions that are made to cruise at AC motor rpms. 

Hope that helps.


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## Jan (Oct 5, 2009)

Glaurung, 

yes it’s a Hi/Low box. But not one that is standard in a 4x4. 4x4’s normally have a transfer case with a high 1:1 and a low e.g. 2:1. This box adds more options to those 2. But how many and what ratio’s exactly is not clear to me.

But your point about such high RPM’s is a good one. 

Dragonsgate,

My toy is at the moment all over the place. It ‘s completely disassembled. The parts are coming in for the next phase: the actual rebuild. And I’m replacing every bearing and seal I’ve found. So, that should solve itself.

But what do you mean with third member? The extra options the toybox offer? 

DanGT86,

I don’t think the toybox is something to bolt two transfer cases together. In the pictures you see it mounted between a transfer case and the gearbox. So it must do something by itself. 

I have placed some questions at Marlin, but no answer yet.

Like Glaurung already suggests, you also suggest a non-gearing solution. A chain belt. That might be a better way to explore.

Thanks all.


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## dragonsgate (May 19, 2012)

I am a heck of one to naming parts as I get the names mixed up myself. Lock outs are usually referring to the front hubs. What I should have called it is a locker. It is a differential that you can manually lock into a straight live axle. The spiders are locked so the axel turns as one piece. What happens with the stock axels is when you get them cocked with one wheel high on the front and one wheel on the opposite side in the back high leaving the other two hanging the two low ones will usually just spin and you don’t go anywhere. With the lockers the two high wheels will pull you on through.This comes in handy for slow jeeping where you can't just power on through. I had some on my Toy in 78 when I was doing some hard rock jeeping but switched back to the stock melons around 1980. I have seen reduction boxes on Jeeps and Toyotas but none of them turned much over four to five thousand rpms that I know of. Some of the four wheel drive meets I attended had slow races. It was funny watching a FWD with a big V8 revving out and moving slower than old people walk.


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## ruckus (Apr 15, 2009)

Jan said:


> I've just ordered the siemens azure combo. And am researching gear reduction. My donorcar is a Landcruiser BJ40. That's a FJ40 with a diesel engine.
> 
> I've discovered the world of crawlers. But the english jargon is making me a bit insane. Do I understand correctly that marlin's toybox is an option for me?
> 
> ...


NO. Your landcruiser parts are designed for 3,000 rpm. If you went with a 'doubler' you could potentially run direct-drive to the transfer-case and throw away the transmission. Or, just use the stock transmission/clutch setup and use the crawler money on batts.


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## dragonsgate (May 19, 2012)

The FJ40 had a six that produced 230 ft pounds of torque @2,200 RPM. I would imagine the diesel engine is probably close to that with maybe a little more torque. I have a 350 in mine and have seen 454’s. The Toys I have seen are pretty tuff. If I maybe be so bold as to suggest that you concentrate on getting the Land Cruiser up and going using the stock parts and then do the mod’s and add-ons’. It is best to do one dream at a time so you do not lose track of the original goal.


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## Jan (Oct 5, 2009)

dragonsgate said:


> I am a heck of one to naming parts as I get the names mixed up myself. Lock outs are usually referring to the front hubs. What I should have called it is a locker.


I don't have diff locks. And don't think I need them. I have the same dissability, and added to that I have to know the enlish names for researching online and the dutch name talking to my dutch garage, or friends. I get confused a lot. 

Your point of keeping it simpel and modify later is a good one. I already have that in mind. But if I have the time I like to research my (future) options. Just to get an idea what it means: Most of the times it's better to do it later. Sometimes it's better to anticipate in the current solution, or do it now, now the cruiser is still a big puzzle.


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## Jan (Oct 5, 2009)

ruckus said:


> NO. Your landcruiser parts are designed for 3,000 rpm. If you went with a 'doubler' you could potentially run direct-drive to the transfer-case and throw away the transmission. Or, just use the stock transmission/clutch setup and use the crawler money on batts.


The transmission is already gone to a better place. I didn't want to rebuild the thing. My option is to bolt it directly on the transfer case, and have the low gear for reasonably peppy performance. And add a toybox like device later. Or a chain drive. I'm researching that.


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## ruckus (Apr 15, 2009)

Here is what you are up against:

Stock torque = gear ratio x engine torque.

3speed = 2.757 x 300Nm = 827 Nm
4speed = 3.555 x 300Nm = 1066 Nm

So you need 800-1000Nm going INTO the transfer case to replicate stock performance. It will 'drive' with less than that, but you mentioned going off-road..

It sounds like you bought the Siemens and the DMOC? This is a low-torque, high-rpm system. It would be best with a transmission or gear reduction.

Siemens at 400A = 298Nm, about the same as the stock motor. You need 2-3:1 gear reduction to make it driveable. This could come in the form of a 'doubler' that is always engaged, or in the form of a transmission.

If you run a doubler on the highway you should be prepared for serious gear noise and failure at those rpm's. You cannot run a jack-shaft chain reduction at those rpm either. Not many designs will hold up at 6-10,000 rpm continuous on the highway.

So it all boils down to the simple fact that you need more torque. A transmission is the easiest way to achieve this. Otherwise you might to consider swapping your motor/controller for one with a higher torque output.

I am doing direct-drive in my project (1936 IH), but my motor should put out over 500 Nm, or about 170% of the Siemens. I also have 4.88 differential gears vs. 4.11 in your cruiser.

500Nm x 4.88 = 2440 Nm at the axle shaft
298Nm x 4.11 = 1224 Nm at the axle shaft. About half. 

A used 3-speed transmission is probably your cheapest and easiest remedy. Or go with a Powerglide?

Cheers


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## Jan (Oct 5, 2009)

Hi Ruckus,

The original engine had a peak torque of 150Nm. Maybe it was more when it was still young. So, max torque the original setup could put in to the transfer case was 150*3.6 = 540Nm. 

But it is hard to compare the max torque of an engine to that of a AC motor with a completely flat torue curve. I actually thing that with 300Nm flat, you don't get much less than a curved 540Nm max.

I guess you actualy have to compare the surface area of the two graphs. And than the flat 300 winns.

I know I'm not exploiting this motor to its full capacity. But an original gearbox is also not designed for such high rpm's. There is no simple soultion.

My idea for now is to keep it simple. And later see what comes along as a better solution. The Toybox e.g. is a kind of doubler. With 2.28:1 it's a perfect doubler. And because it has the same faces as the transfer case, it's not hard to add it later. And than again, nobody knows what rpm's that box can handle. Nobody builds for 10.000 rpm.

Ofcourse I preferred more torque and lower rpm's. Like the Scott. But this offer I simply could not resist. And it's so nice and shiny...

p.s. wiki tells me that it once was 191Nm when it was a young boy.


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## ruckus (Apr 15, 2009)

Jan said:


> ...The original engine had a peak torque of 150Nm...
> p.s. wiki tells me that it once was 191Nm when it was a young boy.


The diesel engines ranged from 191Nm to 319Nm.

191 x 3.6 = 687Nm
319 x 3.6 = 1148Nm

The transfer case can handle much more. They are very strong.


I say build it and see what happens. That is the only way to know...

Again, 298Nm should allow you to 'drive'. The question is how will it do off-road in deep mud and steep terrain? Probably not good. If you are only going to do light off-road and use the 4x4 for snowy/icy roads, then you should be fine.

Cheers


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## Jan (Oct 5, 2009)

Yep. The torque is no problem.


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