ive been sittin ehre talkin to a buddy and were trying to fiqure out the crawl ratio. for an auto.

to my understanding its

tranny x 2 (tourque converter) x x case x gears = crawl ratio..

is this correct or is it

trany x case x gears..

i knwo this is weak tech.. ive been thru google thru pbb search and a ton of sites.. and i swear i read sum place that it was times 2 for the t/c


thanks
payton

tranny first gear x t-case low x axle gearing x t/c if you got one...

That is the rough way for figuring it with an automatic and is close enough.

Originally posted by Wilson
That is the rough way for figuring it with an automatic and is close enough.

my way is close or 44 runner?

Originally posted by payton


my way is close or 44 runner?

your way...

you assume the torque converter is going to give you a multiplier of about 2.

44runner's way is correct for a manual tranny.

The way I see it, you both are saying the same thing....suppose your first gear is 2.73:
2.73(tranny) x 2(TC) x 2.63 (Tcase) x 5.43 (R&P)

-edit- I suppsoe he should have put in a 2 for his T/C at the end of his equation.

thanks for makin sense outta my crown and coke ramblings.. hahaha .. i knew i was on the correct path..

thanks guys

You really can't compare manual vs. auto tranny crawls, but a 2x is a close approximation for a single stator T/C...

BUT.. 1 crawl point per inch of tire seems to work well for an auto.. 1.5x if you like to go stupid slow and have great brakes.

Originally posted by Eskimo
You really can't compare manual vs. auto tranny crawls, but a 2x is a close approximation for a single stator T/C...

BUT.. 1 crawl point per inch of tire seems to work well for an auto.. 1.5x if you like to go stupid slow and have great brakes.

...and to elabroate on this subject you add this into the equation:

3.14xtire diameter = circumference.

example: 3.14x39.5"=124.03"

To crawl 1" per motor revolution you would need a crawl ratio of 124.

My setup is 2.52(trans)x2(TC)x3.96(tcases)x4.56(axle)=91.01

Meaning, my truck is not crawling at the optimal 1 inch per revolution. It seems to work fine here in the midwest, but I'm pretty sure the truck would work better on the rocks if I lowered the crawl ratio a bit closer to 124.

After going auto in mine I would say the Torque convertor is more like 1.6-1.8 and not 2 with a stock convertor

Ryan

What the 2 for the torque converter is talking about is the torque multiplication not the speed ratio.

If the engine is putting out 100lbft of torque at 1500 RPM the transmission input shaft could see as much as 200lb feet of torque at about 400 RPM. This would be with a torque converter stall speed of about 1300 RPM. That is where the 2 comes from.

The 2 is an approximation it can be higher or lower depending on how the converter is designed and manufactured. It is a lot lower on the old/cheap aftermarket converters that are made by beating on the fins with a hammer inside a used stock converter. It can be as high as 2.2 on an expensive aftermarket or modern factory converter with fins that are shaped like an airfoil. This number also isn't important at all to a rock crawler because we have enough gearing down stream of the converter to get plenty of torque at the wheels.

As far as the actual crawl ratio is concerned the converter multiplier could be infinite if you let the converter slip a lot or ideally most of the time on the trail it is 1. meaning no slipage in the torque converter when you are just cruising on the trail. This keeps your tranny from overheating. You just want to use the torque converter for the tough obsticals. Also those high quality torque converters make less heat for a given amount of slipage.

Originally posted by Wilson
The way I see it, you both are saying the same thing....suppose your first gear is 2.73:
2.73(tranny) x 2(TC) x 2.63 (Tcase) x 5.43 (R&P)

-edit- I suppsoe he should have put in a 2 for his T/C at the end of his equation.

oops, my bad. I did mean to put x 2 for torque converter if you have an auto...

Originally posted by Gordon
What the 2 for the torque converter is talking about is the torque multiplication not the speed ratio.


Mabe I am missing something, or didn't understand what you are saying; but isn't the torque multiplication and the speed ratio directly related. You can't get something from nothing wether it is using a lever, gear, hydraulics or energy of any kind. Since the speed ratio is directly related to tire size and the force that you are puting aginst the gound is directy related to tire size I would think that the 2 for torque converter slip would come into the equasion when you were sliping the torque converter to its max.

Other than that I agree with most everything you said.




By the way, who came up with this speed ratio thing, and the optimum 1"/engine rev? Never herd it before. It is a good idea when bench racing wheeling rigs. Probubly a beter way to show how low geared you are than crawl ratio alone.

X2 for a STOCK converter is very generous IMO. When I had mine built I had it modified just to get to 2.0 to 1 at full slip which technically doesnt even move the vehicle. (77 AMC TH400) I was told that the stock full slip gear multiplication ration for most american torque converters is more in the range of 1.25 to 1.5 to one, And this was buy someone that only builds torque converters for a living, and a lot of them specialized. Not saying they were then end-all, but I believed them..........:confused: Anyone care to add?


Ryan

Originally posted by rcurrier44
but isn't the torque multiplication and the speed ratio directly related. You can't get something from nothing wether it is using a lever, gear, hydraulics or energy of any

You are right you can't get something for nothing and the way a torque converter works you don't get anything very efficiently, like you said if it was 100 percent efficient then to double the torque you would get half the shaft speed. but in reality with a torque converter to double the torque you get 1/4 or 1/8 the speed and a whole shit load of heat. that is where the extra energy goes.




Yeep, I would not doubt the numbers you said. The person that explained this stuff to me also builds custom torque converters, and I just posted numbers as an example for explination. They probably aren't the exact same numbers he told me, just sort of a ballpark reference. I should have stated clearly that the numbers were just an example. I got to see a TH350/400 converter cut open and also I think it was a honda converter cut open, you could see how there would be a big difference in efficiency.

But the 2.2 torque multiplication is what he told me he could do. Maybe that's like how a flowmaster adds 25 HP. but that is the type of number some shops are quoting for a tweaked converter.

"Torque multipliers" of an auto is a shameless attempt by slushbox junkies to argue their way into gear-box crawl territories.

Simple fact.

Your rig and My rig, same motors, same tires, same R&P gears, same t'case.. one with a 3:1 auto, one with a 6:1 stick (or even a 5:1 stick)..

Who is going to crawl slower? Put it in gear at an idle... who's going slower/faster?

The stick is the slower rig at idle because it has a lower crawl or final gear ratio than the auto. The "2x multiplier" doesn't apply.

If the auto is slower.. either the convert has too high of a stall, or it's worn out! :flipoff2:

I like the autos in some of my rigs.. but I like the 4spd even more on the trail.

Originally posted by tsm1mt
"Torque multipliers" of an auto is a shameless attempt by slushbox junkies to argue their way into gear-box crawl territories.

Simple fact.

Your rig and My rig, same motors, same tires, same R&P gears, same t'case.. one with a 3:1 auto, one with a 6:1 stick (or even a 5:1 stick)..

Who is going to crawl slower? Put it in gear at an idle... who's going slower/faster?

The stick is the slower rig at idle because it has a lower crawl or final gear ratio than the auto. The "2x multiplier" doesn't apply.

If the auto is slower.. either the convert has too high of a stall, or it's worn out! :flipoff2:

I like the autos in some of my rigs.. but I like the 4spd even more on the trail.


and one word of the dribble you just posted affects teh topic of this post in what sense.. oh it dont.. no one is arguing .. bout the stick to auto debate so get over it. your just trying to make ur slef feel better over having a 4 spd.. i chose the auto over the 4 spd..


so sum one put it in laymens terms the mathmatically formula.. theres gotta be one..

payton

Originally posted by payton



and one word of the dribble you just posted affects teh topic of this post in what sense.. oh it dont.. no one is arguing .. bout the stick to auto debate so get over it. your just trying to make ur slef feel better over having a 4 spd.. i chose the auto over the 4 spd..


so sum one put it in laymens terms the mathmatically formula.. theres gotta be one..

payton

To sum it up.

Mathematical formula of "crawl ratio" is easy.

1st gear * t'case low range (* doublers, whatever) * diff (* portal).

It's pretty simple.

Torque converter has nothing to do with it.

Is that simple enough for ya?

BTW, I really do like my auto.. but not in my crawler. Just in the WFO rig.

Originally posted by payton

so sum one put it in laymens terms the mathmatically formula.. theres gotta be one..

payton

I worded my first post carefully and I still feel it is the simplest way to do it. It is a "rough" estimate by all means, but about as close as you're going to get without a ton of work and in the end is all of that work really worth it? The rig will still drive the same on the trail no matter what the numbers tell you. 2x is overkill but it is safe, if 1.5 or 1.75 makes you feel better go for it (hell, I've heard somsbody use 3 one time, lol). As was mentioned, the T/C will be locked up most of the time on the trail anyways, it's when you hit something that this calculation will apply.

Some of you are speaking of a torque convertor running at 1:1 and that just wont happen unless you are going down hill or have a true "lock up" convertor. Some companies are offering these for drag race transmissions to acheive higher mph in the quartermile. $$$

My current setup is an auto with a final of 49:1 no multiplication, and a stock convertor. This does great on the trail and comps and does not need to be any lower

My last set up in the same Jeep was 77:1 with a manual and was just a little bit slower at idle but not much.

My other Jeep was 55:1 with a manual and same tire size, my auto has a much slower crawl.

Based on my experience I would say the multiplication at idle works out to 1.5-1.6 and increases to about 2 under load.

Ryan

Can someone help me out.. what's my "crawl ratio" when I slip the clutch with my manual tranny?

The "auto crawl ratio advantage" is no different than slipping the clutch.

Once you're moving you're close to 1:1 - in the meantime you're abusing your auto or your clutch getting going.

Launching my slushbox rig at 3k due to the higher stall converter is no different than side stepping the clutch at 3k (though admittedly, a lot smoother!).

Hi so your all talking abot the TC torque multiplication, but shouldn't we be taking about the difference in engine rpm and transmission input shat rpm to determine the effect on crawl ratios? A TC with a torque multiplication of 2 isn't dividing the rpms by 2. It's probably more. Let's just say its 4. 2000rpm in with 200 ft lbs. out we'll have 400 ft pounds and 500 rpm. and a bunch of waste heat. So the torque multiplication is 2 but the effect on the crawl ratio is 4. Crawl ratio is looking at your gearing from a speed point of view, not torque. But then again I don't know much. I push electrons around for a living. (My rig is going auto cause they're magic inside, And I want my rig to be magical:) )

Originally posted by BlueMoose
Hi so your all talking abot the TC torque multiplication, but shouldn't we be taking about the difference in engine rpm and transmission input shat rpm to determine the effect on crawl ratios? A TC with a torque multiplication of 2 isn't dividing the rpms by 2. It's probably more. Let's just say its 4. 2000rpm in with 200 ft lbs. out we'll have 400 ft pounds and 500 rpm. and a bunch of waste heat. So the torque multiplication is 2 but the effect on the crawl ratio is 4. Crawl ratio is looking at your gearing from a speed point of view, not torque. But then again I don't know much. I push electrons around for a living. (My rig is going auto cause they're magic inside, And I want my rig to be magical:) )


now I'm really lost!:confused:

Originally posted by BlueMoose
Hi so your all talking abot the TC torque multiplication, but shouldn't we be taking about the difference in engine rpm and transmission input shat rpm to determine the effect on crawl ratios? A TC with a torque multiplication of 2 isn't dividing the rpms by 2. It's probably more. Let's just say its 4. 2000rpm in with 200 ft lbs. out we'll have 400 ft pounds and 500 rpm. and a bunch of waste heat. So the torque multiplication is 2 but the effect on the crawl ratio is 4. Crawl ratio is looking at your gearing from a speed point of view, not torque. But then again I don't know much. I push electrons around for a living. (My rig is going auto cause they're magic inside, And I want my rig to be magical:) )

Sure sometimes it is 4 sometimes it is one and sometimes it is 2456. that's the whole point with an auto when the torque converter is slipping you can make the crawl ratio whatever you want by modulating the gas and brake simultaneously

Originally posted by Gordon


Sure sometimes it is 4 sometimes it is one and sometimes it is 2456. that's the whole point with an auto when the torque converter is slipping you can make the crawl ratio whatever you want by modulating the gas and brake simultaneously

Ah some sanity :cool: