[Rastus]

Is 42 to 1 a decent crawl ratio?

I read this "Crawl ratios in the 60's are quite capable; in the 80's, very respectable, in the 110's, impressive and anything beyond the 130's is usually considered the point of diminishing returns."

there's no way with my current axles I can get any lower than 50-1. How noticable will the difference in the two be?

 

[4x4Freak]

I had aprox. 45:1 (assuming 3:1 for the torq. conv.) in the scout with the 3.07s. It has about 67:1 now with the 4.56s and I still feel like it could use some more, but it does pretty good.

I'm sure you can get lower than 50:1. Are you taking into consideration the mutiplication of the torque converter?

 

[Rastus]

I have a stick.

1st is 3.83
xfer is 2.72

with 4:88's I get 50.8 to 1

with 4:10s I get 42 to 1

4:88's are the lowest available for a D30

with the 3:07's I'm at 31.98 to 1

 

[4x4Freak]

Oh, ok.

What tires do you plan to run?

 

[Rastus]

36" TSL's

 

[4x4Freak]

Hmm, you would be pushing it especially with a man. tranny. I think your best bet would be to find someone with the same setup and see what they think about it.

I have a 47.89 ratio in the K10, but having a BB makes up for the lack of gearing.

 

[Rastus]

I think 4:88's are in my future 8)

 

[4x4Freak]

They would be better than 3.07s for sure.

 

[JP_CT]

Is 42 to 1 a decent crawl ratio??

Depends on what you want to crawl on. I was at 119.5 in my Zuk

 

[OldGoat]

sidebar question???

Zach, please explain the way a torque coverter multiplies gearing? I basically understand the workings of it and how the stall RPM can be changed etc. but this is a new one to me. If the torque convertor were 3:1 then when the tranny was in the final gear or even overdrive the ratio would not be 1:1 or overdrive ratio, right? I am confused, straighten the oldgoat out here. lol

My ratios are auto tranny 1st gear 2.45:1. plus x-fer case 2.60:1 low range, plus final differential ratio of 4.56:1 for a total of 29.05:1 which sux going downhill!

 

[fourwheelerjeff]

on my 86 blazer i would like to run 2.48 (turbo 400) 3:1 (203) 1.98:1 (205) with 5.86 in the differentials which would be 86.32 for a crawl ratio

on the 88 blazer i would like to run 3.06 (700r4) 2.61:1 {208} with 5.13's on the differentials for 40.97

91 xj has 2.8 (aw4) 2.72 (231) and 4.56's for a ratio of 34.73; if i can afford a rock trac transfer case (rubicon) i would like to put it in there for a 2.8 with a 4:1 and 4.56 would give 51.07

all these are not taking into account the torque convertor smokin

 

[OldGoat]

getting down

Now that 86:1 is getting on down there!

 

[Hatch]

At best, figure 2:1 for your torque converter (I use a conservative 1.5:1). This multiplier is the slippage you get before it hooks up (there's always some slippage unless you have a lockup TC).

Tires make a difference, but tires are never figured into the equation (too many variables I guess). When I first went from 35s to 38.5s, my CR was 1.5*2*2.26*5.38 (TorqC, Turbo 200 Low, Sami Low Range, R&P) = 36.5 (48.6 w/2:1 TC). I had a lot of trouble getting up steep stuff.

Then came 4.16:1 low range: 67.1 (89.5). Much improved, but with a dying carb and then the slight loss of power with the propane switch, I lost a little bit of climb-ability (crawl is still very good). If I were still running 35s this setup would really rock (but I'd hang up a lot).

What's coming? With the 4.3 swap I will dramatically increase power AND...
New CR 1.5*3.06*2.62*4.16*5.38 = 269.1:1 (358.9:1 w/2:1 TorqC factor)
[Torque Conv, 700R4, NP208, Sami t-case, R&P]
I'm thinking that maybe I should go back to stock Sami t-case gears 2.26; CR=146.2:1 (195:1). Or maybe I should buy bigger tires.

Or sell my 4WD 700&208 and get a 2wd 700R4: 1.5*3.06*4.16*5.38=102.7:1 (137:1). Nah. Too fast!

 

[4x4Freak]

The torque converter slippage lets the engine rev up more and lets you crawl easier. The more rpms you turn the more the torque converter grabs. A higher stall just doesnt grab as much until you reach a higher rpm. Think of holding your hand out the window going down the highway. If your going slow its easy to move your hand forward, but the faster you go the more air resistance there is on your hand and its harder to push forward. It's the same basic concept with a torque converter, the faster the fluid moves, the more force it puts on the turbine that drives the transmission. If you want to learn more or just dont understand my explanation go here: http://auto.howstuffworks.com/torque-converter.htm (thats a pretty cool site, btw)

It doesnt give you a lower gear ratio, it's just more forgiving to a higher gear ratio. That's the reason most autos have a 2-3 first gear ratio, while man. typically have a 3-7 first. With a man. tranny you have to slip the clutch more with a higher ratio. If you do this much you will smoke the clutch. The torque converter is basically like slipping the clutch, only it is more controlled and if you have a good cooler it will last. This is the reason you can typically get away with a higher gear ratio if you have an auto tranny.

I have heard different figures for the torque mulitiplication, but the one I've heard most is 3:1 so that's the one i usually use.

Did I completely lose you yet? lol

 

[Hatch]

http://www.novak-adapt.com/knowledge/gearing.htm

I've been studying this crawl ratio thing for quite a while and I've never ever seen a 3:1 factor mentioned for a torque converter (until now, in this thread). The above link is not the only place I've seen this info.

 

[kling-on]

put a 4to1 in that 231 as well bigok

ad if its your chevy double case it :bling:

 

[4x4Freak]

http://www.novak-adapt.com/knowledge/gearing.htm

I've been studying this crawl ratio thing for quite a while and I've never ever seen a 3:1 factor mentioned for a torque converter (until now, in this thread). The above link is not the only place I've seen this info.

Just because you havent seen it, doesnt mean I havent. I would think it would vary depending on the stall speed anyway.

 

[Rastus]

put a 4to1 in that 231 as well bigok

No, I'm going with a dana 300 flipped. then later on get the 4-1 gears for it.

 

[hbar314]

I guess ill throw my 2cents in.
In my toyota im running:
1st: 3.93
tcase:4.70
axles:5.29

Which gives about 98:1.
(man tran)

For my 4cyl i really love being this low. If you have more motor then you shouldnt need anything this low. It all depends on your setup.

My buddy has a 4.3L in his toy and gets away crawling the same stuff with stock tcase(2.28:1) and 4.88s in the diff.

 

[Hatch]

Fair enough.

I'll stick with personal experience to back up everything I've read and been told by gear gurus. 2:1 seems reasonable, 3:1 is wishful thinking. Unless your TC slips too much, and then you get extreme heat buildup. Perhaps an aftermarket TC could get you more slippage.

Seems like a higher stall speed would be worse: when it finally grabs, you're RPMs are so high you can't crawl anymore.

Just because you havent seen it, doesnt mean I havent. I would think it would vary depending on the stall speed anyway.