For those who run really low gear combos

Madgyver · Dec 6, 2003

Just wondering, How low is necessary?
125 to 1?
200 to 1?
Low enough to play on the rocks and still be able to drive the long miles pleasantly to get there on the freeway.

I know it's good to have a wide range but how low is your lowest combination.
There is alot of options out there i.e. (klune-v, cold duck, NP 203 doubler, Tera lows, BCs D20 low or just plain low axle gears.)

For those who have it. List your set-up

Thanks,
madgyver

broncnaz · Dec 6, 2003

While I have never been in a vehicle with 100-1 my setup is a NP435 stock T-case 3.50 gears and 33" tires works out to around 60-1 maybe a little lower but this setup will idle up a wall if you could get traction I can get out and walk faster than it moves. I dont do a lot of rock crawling but it has worked well for what I have done.

broncobrains · Dec 6, 2003

I've got 70:1 and it works well for me, but our rocks are almost allways wet.

lars · Dec 6, 2003

Mad- I thought my 4.10 gears plus NP435 was plenty low (with t-shift D20 that's about 67:1) until I was on the Rubicon last summer. I was wishing for lower gears. A friend who was along had the same drivetrain as me except for the NP203 double that Wild Horses sells as the Super Creeper. After trying his truck I want one. 130:1 seems crazy low until you need it. An Atlas will do the same thing, but I like the idea of having regular transfer case gearing as well. Downside is that you risk snapping the stock D20 output shaft. So there's an extra $400 to upgrade that. Someday...

Madgyver · Dec 6, 2003

broncnaz said:
My setup is a NP435 stock T-case 3.50 gears and 33" tires works out to around 60-1 maybe a little lower but this setup will idle up a wall if you could get traction I can get out and walk faster than it moves. I dont do a lot of rock crawling but it has worked well for what I have done.

I currently have this same set-up and I feel the need to go lower. I've been in situations where I wished I had lower gears.
Now that I have 37"s a gear change is in order so I'm weighing out my options without going overboard.
I got a 4.11 D-locker under there now and plan to get some kind of crawler case added on or just get deeper gears. Anyway I go it will cost me $$$. Also I don't want to be winding up at freeway speeds, To be right around my peak torque range at 60mph.

Madgyver · Dec 6, 2003

lars said:
130:1 seems crazy low until you need it. An Atlas will do the same thing, but I like the idea of having regular transfer case gearing as well. Downside is that you risk snapping the stock D20 output shaft. So there's an extra $400 to upgrade that. Someday...

Same here, I understand that by having lower gearing and using it wisely you are less likely to break the D20 output shaft and other parts of the drivetrain. It's the heavy right foot that does the damage.

Tazz · Dec 6, 2003

Hey Mad
The low low gears are nice when you need them. but like Lars said it's nice to have the stock low range. I know that I went the $$ way with the klune/Atlas combo, but I use the 2.7 low in the klune most of the time but it is defenitly nice to have the 4.3 when you need it. It only takes a short time in the 4.3 to know that if that was all you had, it's to low for most of the things we do. It might not be bad if you had a 5 speed and could run around in 4 & 5th gear in low range.

SgtRock · Dec 6, 2003

Don't forget auto v manual makes a difference in what low gears you need . . . I am running a C4 with a cold duck and 3.50 gears, its 2.43x2.46x2.46x3.5=51.46 but with the torque converter in there it feels more like 100:1.
Craig
Mineola, TX
'74

Moaiz · Dec 6, 2003

When I get around to finishing my 70' with the ZF, JP Rockeater's and 4.88 gears my final crawl will be:

5.72 X 4.86 X 4.88 = 135.66

I am ultimately planning to run stazworks 17" rims with Krawlers. I figure with the 300M D20 output shaft and moser extreme duty axles I wont be snapping too many things. Now its just about accumulating the income do dispose of.

DoughBoy · Dec 6, 2003

My old Yota had a Turbo tranny ( 4.3 first ), stock t-case, marlin ultimate second case ( with 4.7 low ) and 5.29 gears. Double low was 244 to 1. It doesnt seem necessary until the rocks get bigger and bigger, then it just seems natural. I'd say for serious crawling, either 100 to 1 minimum with a stick, or at least 50 to 1 with an auto will get you by, anything more just makes everything easier

broncnaz · Dec 7, 2003

since you already have a NP435 you may want to try Rockeater gears for the T-case 4.86-1 or Tera lows 3.15-1 less over all mods needed and as you know if low range 1st gear is to low you can always shift. although the 203 doubler case only adds an 1 3/8" should be to much problem fitting that in

Broncobowsher · Dec 8, 2003

My combo that I like runs good on the highway and does almost everything else well.
4R70W, tera, 4.88 thus 2.84 x 3.15 x 4.88 = 43.6 with an automatic so you have double that with the converter. That converter also makes the ultimate slipper clutch.

You can always go slower and lower, but I like what I have. If I were to do everything over again, maybe 4.56 gears and a 3.8 atlas.

Allen_69 · Dec 8, 2003

Not to hijack your thread, but has anybody yet looked at a ZF-203-D20 combo yet? I looked thru advanced adapters website, but couldn't find anything for a zf-203 adapter. I would think that combo would get me to about 175:1 and still retain my 4:10 gears.

Dusty · Dec 8, 2003

Moaiz said:
I am ultimately planning to run stazworks 17" rims with Krawlers.

I'd do some research on those Krawlers before plunking down the cash for them. Ask Tonto.

Back to the thread, I'm running stock C4, stock D20 with 5.13s and 35s, and an injected 351. I seem to get enough TQ slip to finesse it up the rocks, but I like having regular low for when I need to build speed to "bounce" up over something, and of course for the 90% of the trail where regular low is more suited than super-duper low. Like has been said, an auto is more forgiving. But the auto with non-super low gears has a "con" on the downhill side, as you don't get very good compression braking. I still would like someday to go to an Atlas though just because its stouter than my old D20, that I tend to worry about because I beat it pretty hard. Maybe the 3.0 highlander Atlas would be the best choice for me.

Dusty

david heater · Dec 8, 2003

I love to have control, i learned a long time ago speed is great where the land is flat. add rocks and the name of the game is control.
so in the standard configuration being a stock "J " shift dana 20 mine looks like this.
NP435= 6.69
T-case= 2.34
R & P = 4.56
which equalls 70:1... not bad not real good either..

but that is not the question, I reach over a shift the cold duck into low and now it looks like the above except you add

2.46
now you have 176:1 And I will idle up anything as long as traction can be had...now I have control...Which is nice to have when the rocks get big..plus it is funny watching the jeep guys beat there TJ's up while i idle up what ever they thought was a pain....;D

Past_Miner · Dec 9, 2003

Allen_69

I've been working (slowly) on a ZF/203/D20 set up for a few months now. I have a 203 off of a Ford C6 that bolts up to the ZF. The problem I have with that box is the left hand shift bulge in the 203 housing interferes with the D20 shift rails. I think I could solve that issue with a longer adaptor between the 203 and D20, but my goal is to close couple those two boxes.

I picked up a Dodge box last weekend. That box has a right-hand shift, so the interference should go away. According to the sources I talked to, the input gear from the Ford box will go right into the Dodge box. After that its just a matter of drilling the correct bolt pattern into the 203 to match the ZF. The other issue is that this set-up starts to get pretty long. However, I think it can be done and leave a long enough rear driveshaft to keep from eating u-joints.

Now if I just had the cash and liked to do things the easy way, I would buy the WH 203/D20 kit, slap my input gear into it and drill the 203 face to match the ZF. I don't think its very difficult to do with the kits that are already available. Just takes the $$, but what doesn't?

Madgyver · Dec 9, 2003

david heater said:
I love to have control, i learned a long time ago speed is great where the land is flat. add rocks and the name of the game is control.
so in the standard configuration being a stock "J " shift dana 20 mine looks like this.
NP435= 6.69
T-case= 2.34
R & P = 4.56
which equalls 70:1... not bad not real good either..

but that is not the question, I reach over a shift the cold duck into low and now it looks like the above except you add

2.46
now you have 176:1 And I will idle up anything as long as traction can be had...now I have control...Which is nice to have when the rocks get big..plus it is funny watching the jeep guys beat there TJ's up while i idle up what ever they thought was a pain....;D

What size tires are you running?

david heater · Dec 10, 2003

Madgyver said:
What size tires are you running?

I ran 35's this past fall, but normally run 36"

mxpaz · Dec 10, 2003

I have a 203-205 doubler behind a C6. Its pretty good Im at around 60-1. If you are gonna go with a stick and rock crawl at a min you need 100-1.

elemetal · Dec 10, 2003

I'm running 35's, 3.7 diff, Atlas II low (4.3) and my first is about 4.9 or so (AX-15). That's about 80:1 which does everything I've needed so far, but 4.11's would be the next step. Good thing is it'll do 80 on the highway @ 2400 rpms and you can shift the Atlas on the fly on the trail and get low. If I put in a NV 4500, 1st comes down to 5.56 or something so the ratio will be close to 90:1 with a .74 overdrive. It works a large part of the spectrum.

For those who run really low gear combos

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