Shane´s 8 to 1 t-case with stock diffs got me to thinking...........

What are your collective thoughts on gearing distribution throughout the drivetrain?!? My common sense tells me that the more spread out among the various components, the better. However, my common sense has been known to fali me :p and some of you guys seem hell-bent on concentrating the reduction in the t-case. What is the advantage of this?!? Is it cost driven or is there some tech reason that I´m not seeing?!?

My rig´s gonna be set up as follows:
- 1.6 16 V Swift motor
- Vitara auto tanny (2,83:1 first gear)
- Vitara 1,81 t-case into Samurai 4,89 t-case
- 4,88 diffs in D44s
- 38.5" SXs

This will give me a 122:1 ratio in low-low and IMNSHO, the loads will be pretty well spread out along the drivetrain.......

Thoughts?!?

Cost and flexability. with 4.10 toys and the 2 tcases (tracker and 4.16) it is spot on for
the 35's I am running. (speedo is within 1.5MpH by GPS)

I'm thinking more bang for the buck as well.... Everybody know's Suzuki people are cheap at heart:D

Gearing the ring and pinions down does relieve some of the stress the drivetrain further up the chain sees. I believe with the Samurai gearboxes being so small and light that a lower ring and pinion ratio is beneficial to their longevity. Most of the people I have talked to who have experienced multiple case failures had stock ring and pinions.

This setup is only staying on here long enough for me to put my toy axles with 5.29's. But at that I will be on 37's and be 155:1:D

But I think its almost a toss up for strength.....aftermarket r&p's for zuk axles being so small and easy to break....Id go with the tcase gears.

You can always use those with other axles later:D

Hi torque require high strength, heavy expensive parts. Keep rpm high as far as possible through the drivetrain. Those portal hub/axle thingees are ideal for this. As an example, yeah, I know they don't build em for Zukes.
A catapillar tractor (well, most tractors) have giant bull gears as the last stage in the drivetrain. This has a lot of reduction in it. If they didn't use this arrangement the rest of the drivetrain and bearings would have to be much heavier.

If, for a given load, you compare two setups with the SAME final dirve ratio. One with stock diff gears and one getting there partially though lower R&P gears, the one with lower R&P gears will divert some of the torque from the tcase to the diffs. This would help with busted cases and arms.

If you take an existing setup and add lower R&P, increasing the overall reduction, the rear wheels will have now the ability to put a greater max force to the ground than before. If the force required to move the rig is the same, as it normally would be, the tcase will see a reduce load. If however you get bound up, and give it the gas, the case will still see the same load as before and may go bang, or your axles may go bang from the increased force on them.

Bottom line, spreading out your gearing is a good idea, but no guarantee.

If, for a given load, you compare two setups with the SAME final dirve ratio. One with stock diff gears and one getting there partially though lower R&P gears, the one with lower R&P gears will divert some of the torque from the tcase to the diffs. This would help with busted cases and arms.

I agree totally. The tranny gears and bearings would see more rpm for the same speed and load, and less torque. I could say it another way, since torque x rpm = power, I could say for a given power through-put, this would be easier on trannys and mts, but the diff would see the same load as before.


If you take an existing setup and add lower R&P, increasing the overall reduction, the rear wheels will have now the ability to put a greater max force to the ground than before.

Exactly.


If the force required to move the rig is the same, as it normally would be, the tcase will see a reduce load.

Yes!


If however you get bound up, and give it the gas, the case will still see the same load as before and may go bang,

Yes! The tranny will see the total max torque available from the engine, the t-case will see that torque multiplied by the total reduction dialed in at that moment from the tranny.


or your axles may go bang from the increased force on them.

Yes! We have magnified the torque, every component 'seeing' this torque should be sized to handle it.


Bottom line, spreading out your gearing is a good idea, but no guarantee.

Well, now, wait a minute. If by this you mean, to do some of your reduction in the t-case, and some at the diff is better IN THEORY than doing it all at the diff, then, NO that isn't true. You want to magnify the torque at the last possible moment. 'Course we don't have that kinda choice outside of a discussion like this, those kinda components aren't available.

Suppose I divided up my new desired reduction, and put a 4:1 t-case gear in instead of the 8:1 I wanted, and put the other 2:1 in the diff (it don't matter how) then the output of the t-case and the u-joints would see more torque and suffer for it, and so would the input to the diff (pinion bearing). Put ALL 8:1 in the diff, then only the output side of the diff sees the heavy torque that breaks things. This would NOT be the ring gear, but the hub, spider gears and side gears and axles, axle bearings, etc.

In school, did you ever hear of "equal but opposite reaction"?

The torque at the flywheel is the same as the torque at the wheels. The weakest link will fail where ever it is.

Bottom line, spreading out your gearing is a good idea, but no guarantee.

GeoB, Nothing scientific here, I just meant that you can certainly still break shit. :D


Fliiper, go re-read your text book! The amount of work done by the engine is the same as that done by the wheels, but the force is definitely much greater at the wheel after going through all the gear reductions. If what you said was true, we wouldn't need gears.

This is pulleys, but same concept as gears: http://science.howstuffworks.com/pulley.htm

Jim's got it. The whole purpose of the gears is to multiply the torque. The "equal/opposite" principal applies to the t-case mounts talked about above as an example. The gear reduction (i.e. torque increase) in a gear box is directly related to the force transmitted to the case and connections. By distributing the gearing throughout the drivetrain you are dividing the "work" being done across multiple components which reduces the stress on each one.

In school, did you ever hear of "equal but opposite reaction"?

The torque at the flywheel is the same as the torque at the wheels. The weakest link will fail where ever it is.


WRONG!!!!!!!! :rolleyes:

Johnny, what do we have as consolation prizes for this shit-spewing asshat?!!?

:flipoff2:


Discounting friction, what´s the same at these points is POWER. Torque is much higher at the wheels, inversely proportional to the gear reduction.

:)

Just a small point - Watching one of those "History of 4x4" shows on the Discovery channel, they were interviewing what's-his-name, builder of Bigfoot. Anyway, the point he was making was that monster trucks were in trouble for a while, breaking axles all the time, then someone started the trend to reduction axles - you know, like the hub reduction of a Mog axle, except it was a planetary reduction at each end of the axle. It spread the load out, breakage went way down, and monster trucks really began to perform, to the point where they really haul ass now-a-days.
So putting stress across more points was a good thing.

Okay...I was doing some anti-wrap bar calculations a while back and was trying to figure out some torque formulas. If you take the peak torque at the flywheel (98 lb-ft in my case)...do you just then MULTIPLY it by the crawl ratio to get peak torque at the axle stubs? So at 107:1 crawl, I'd have 10,486 lb-ft of torque??? :eek: Someone correct me, cause that's a LOT of torque!~

monster trucks were in trouble for a while, breaking axles all the time, <snip> a planetary reduction at each end of the axle.

This is great engineering. All kinds of earthmovers are built this way.

It spread the load out, breakage went way down,

I am afraid I am beginning to sound like an asshole here... I am not trying to be RIGHT but only trying to communicate an idea...

It ISN'T that they SPREAD the load, but that they moved the heaviest load to the very last component, so not all the components had to be sized for giant torque.

I believe in spreading stress across many support points, at least I would if I were an engineer and knew what I was talking about. I usta be a motorcycle mechanic. Long time ago. I had a piston collection of ALL sizes. Big thumper pistons, etc. But the LARGEST bearing surfaces were in the BMW R-50 (500cc, 250cc per side). Those lil pistons had more rings and GIANT piston pin. Of course, it was the most long-lived of any of my bikes too.

So putting stress across more points was a good thing.

I agree with this general idea, but I just don't think the planetary reduction is a good example of it.

Hmm. Maybe we are saying the same thing. In order to produce the needed torque for a 1.3 squirrel engine to turn large tires, we all agree we need a lot of final gearing - I think.
So, we all say, for instance, we need a total of 200:1 to get the job done. If the tranny was 4:1, and the axles were 2:1, a t-case reduction of 50:1 would make us happy, except it would take big, big axle shafts to take all the load. Now, putting a gear reduction axle at the end is indeed putting the reduction at the last point, and in this pretend formula lets say they are 10:1 - now the t-case only has to be 5:1 - and the t-case gears get lighter duty, as do the differential gears. If you put all 100:1 on the ends of the axles, everything "upstream" gets to be built even more "light duty", and with less gear reduction. But the gear boxes onthe ends of the axles will not be light.

They will be beefy, to gear down that much in one step.

Which is why we are saying "spread out the load". If you concentration torque mulitplication on any one point, it must be built to take that stress, as must all components that carry the load. An 8:1 gear box transmits a lot of torque thru it's gears, and they are highly stressed, as are the driveshafts, differentials, and axleshafts. "spreading the load" by using low gears in the diff to have gearing with a 4:1 box, the drive shafts are stressed "half"(sort of) as much, and can be built to survive "half" the torque.
Like you said, move some gearing farther down, to the ends of the axles, and the axle shafts get even less load on them. But it isn't as simple as moving it to the end of the line, because everything is a comprimise. 200:1 gear-reducion axles might be too big, and 200:1 t-cases may put too much load on the rest of the driveline.
It is really "spreading the load" thru as many components as you can, within the limitations of what is available.

Capt ron... you are right! thats a lot of torque.


But the horsepower does not multiply because the speed is reduced.

OK, I agree with you. I was attempting to isolate the theoretical principle, and you were being more practical.

Capt ron... you are right! thats a lot of torque.


But the horsepower does not multiply because the speed is reduced.

Ahhh...you very smaaat glasshopper. Or maybe just rucky, you plick! :D

Ahh, no jap jokes prease!

Glass hoppa

I say the further down the drivetrain the better. Someone needs to build a reduction planetary bolt on hub with intgrated brakes that fits inside a 20 inch wheel. You could take your diffs out flip them high pinion style to counter the reverse of the planetary hubs. Many large aircraft tow tractors use standard truck parts all the way to the hubs, and they are geared real low.