Atlas 4sp vs 2sp opinions

ProbablyBroke

ProbablyBroke

does not torque to spec
Joined
Nov 7, 2012
Location
Reidsville
I’m asking for opinions on 4 speed vs 2 speed atlas for east coast crawling and park riding. My experience has always been 80hp Toyotas with manuals with doublers and/or t case 4.7 gears, and 4.10 differentials
Currently have a 5.0 2speed atlas on order that should be coming up for production soon.
The buggy it is going in will be 3rz (150ish hp), 5 speed manual with 5.38 tons, and 40” stickies.
@DannyH and I ran the numbers and there are plenty of options. 3.8 4 speed seems to offer the most useable gears. The chart shows the available 4 speeds with 5.38s and gears 1-5 of a r155f toy trans.
IMG_7459.png


Sooo….. the questions are…
-What is considered a useable gear ratio for the aforementioned buggy? We said anything 40:1 and up.

-Is it realistic to be rowing triple sticks looking for the right ratio?

- folks with 4sp atlas, do you wish you had less gear and gone 2sp?

I’m sure this is all rather subjective, but wanted to bounce it off you knuckleheads.
 
Coming from the 0hp all the gears crowd to some HP and 3.8 2spd with 4.56’s in the axles and a 5spd, the 3.8 fits the bill just fine. On 42’s that measure 39.5 it’s 1st gear for most trails just crawling, 2nd gear crawling at speed, 3rd gear when I’m pissed and want to send parts into the outersphere. I think 5.13/5.38 would make 3rd more usable for wheel speed obstacles but it hasn’t held the rig back yet.
 
With a 5.0 2sp and 5.38s the gears are :
1. 106.2
2. 57.56
3. 37.12
4. 26.9
5. 21.78

I’d like the keep the buggy as simple as possible and spending an extra 1300$ on a bunch of redundant gears would haunt me.

For anyone that doesn’t know, going to a 4sp adds 5”…. Of drivetrain.
 
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You'll never wish you had less gear(s).
Go for the 4 speed so you can pick and choose ratio for selected terrain.
My favorite rig was a YJ with a V8, auto and Klune/205 combo. I used each ratio (2.0, 2.7 and 5.4) for different types of wheeling
I'd add a crawl box to mine if it wouldn't change so much of what MarsFab has already done to th belly skid.
 
I ran a healthy turbo 22re,R151F, 2.28 crawl box to a Land Cruiser split case at 2.28. 39 krawlers on tons w/5:38’s. I loved the gearing options. Only used all out high range when driving highway speeds. If it’s not going cause a driveshaft issue I would definitely go for more gearing options.
 
The 4 spd is great for the options available. Trail to trail 2.72 low in the front box.

Decent hill killing 3.8/4.3 low with the “crawl box” in high and case in low.

Rock gardens or silly slow technical stuff. Both in low and crawl with ease.

If you can fit it, and afford it. It a for sure IMO.

I think a 2.72/3.0 would be too close to take advantage of, and I think a 2.72/5.0 would just be wayyy too much gear, hence why I think a 2.72/3.8 or 4.3 is a great combo.

I’m thinking of trying to put a NWF box in front of my 3.0 atlas in my next build just for the extra options.

From what I can’t tell AA doesn’t want to sell just the crawl box to go in front of an atlas 2sp, or at minimum doesn’t advertise it.

Hence I was looking into finding a 241 donor to put the guts into a NWF box in front of the atlas.

Not trying to muddy the thread but wanted to illustrate the thinking of how much I like the 4spd options.
 
Mac5005 said:
The 4 spd is great for the options available. Trail to trail 2.72 low in the front box.

Decent hill killing 3.8/4.3 low with the “crawl box” in high and case in low.

Rock gardens or silly slow technical stuff. Both in low and crawl with ease.

If you can fit it, and afford it. It a for sure IMO.

I think a 2.72/3.0 would be too close to take advantage of, and I think a 2.72/5.0 would just be wayyy too much gear, hence why I think a 2.72/3.8 or 4.3 is a great combo.

I’m thinking of trying to put a NWF box in front of my 3.0 atlas in my next build just for the extra options.

From what I can’t tell AA doesn’t want to sell just the crawl box to go in front of an atlas 2sp, or at minimum doesn’t advertise it.

Hence I was looking into finding a 241 donor to put the guts into a NWF box in front of the atlas.

Not trying to muddy the thread but wanted to illustrate the thinking of how much I like the 4spd options.
Click to expand...
I put a 2.7/3.8 4 Speed in @thebrotherinlaw XJ a couple years ago. It's a great split of ratios, just like you mentioned.
 
I run a 203/205 for years in my xj. Works well in 1.99:1 with the 42's and 5.38. In double low 3.98:1 it's not enough to crawl things with the weight I have and almost too low for normal crusing the trails. If and when I rebuild I will swap to a NWF crawl box to get that 2.73:1 low that I think will work better with the 4.0. FWIW if you can do the 4 speed I agree with Jody you will never wish you had less gear options.
 
Mac5005 said:
If you can fit it, and afford it. It a for sure IMO.
Click to expand...
I bet you say that to all the guys :D

Mac5005 said:
Hence I was looking into finding a 241 donor to put the guts into a NWF box in front of the atlas.
Click to expand...
What parts do you need out of a 241? I have a whole one with a busted case. The internals are all fine. Assuming you need a planetaryand input, but what else? It could be yours....
 
 
Croatan_Kid said:
I bet you say that to all the guys :D


What parts do you need out of a 241? I have a whole one with a busted case. The internals are all fine. Assuming you need a planetaryand input, but what else? It could be yours....
 
Click to expand...
Input planetary and associated parts.
northwestfab.com

4x4 Drivetrain | EcoBox | Northwest Fabworks Canada

The BlackBox-Eco was designed for the 4x4 drivetrain enthusiast on a budget. Designed to be a DIY builder kit; cases are shipped empty, and the customer provides the gears, and does the install and assembly.
northwestfab.com northwestfab.com
 
Check your PMs @Mac5005 !

Unlike usual NC4x4 fashion, I'll try not to clutter up somebody else's thread 😂
 
The problem is high side just like your old setup. Pending buggy weight, 150 hp is still questionable at best to be pulling high side from trail to trail unless you plan on staying in 5:1 which would freaking suck. 5:1 would be fine for its intended use though because its in the middle of 4.7/ stock dual yota cases gear wise. Imo, 4 speed is the way only because of the 5 speed. 2.72 for trail to trail then 4.3 for a semi low crawl gear. Still the option to double up when needed. 3.8 is too high to slow crawl with a 5 speed successfully. BUT if you put an aw4 in it instead, 5.0 and done. The 5 speed is a loop hole for gearing with low power.
 
This is all great feedback. I just fear that with the 5.0 I’ll have 3 useable gears. Crawl, bump it and party mode.
AA states that there are differences between a 2 and 4 speed beyond just the 2.72 planetary housing. Tech man said you can’t just bolt up a crawl box .
 
ProbablyBroke said:
This is all great feedback. I just fear that with the 5.0 I’ll have 3 useable gears. Crawl, bump it and party mode.
AA states that there are differences between a 2 and 4 speed beyond just the 2.72 planetary housing. Tech man said you can’t just bolt up a crawl box .
Click to expand...
That sounds like sales bs. If the atlas bolts to an aw4, just as an example, then why could you not just bolt a NWF black box in front of it? They all have the same 6 bolt mount right?
 
ProbablyBroke said:
This is all great feedback. I just fear that with the 5.0 I’ll have 3 useable gears. Crawl, bump it and party mode.
AA states that there are differences between a 2 and 4 speed beyond just the 2.72 planetary housing. Tech man said you can’t just bolt up a crawl box .
Click to expand...
I think what they are referring to is that the shifter for the underdrive unit is integrated into the main housing, so you cannot just upgrade your Atlas 2spd to a 4spd with THEIR parts. Like @ghost said though, I would think a standard aftermarket underdrive should bolt up to the front of a 2spd Atlas.

Here is a picture of my Atlas 4spd. I bought it in 2007, and supposedly the design has changed since then.

1688665206163.png
 
ghost said:
That sounds like sales bs. If the atlas bolts to an aw4, just as an example, then why could you not just bolt a NWF black box in front of it? They all have the same 6 bolt mount right?
Click to expand...

You probably can't bolt up an Atlas crawl box. They probably have more integration between the two cases, I would imagine similar to how the Magnum and Titan replace internal parts of a 205.

Duane
 
I’ve mostly wheeled four rigs, and I think the desire/want of TC gearing depends on auto or manual transmission.

Rig 1: 76 GMC Jimmy with TH350 auto and NP203 with 2:1 gears. SUCKED

Rig 2: Full size Bronco with C6 auto and NP208 TC with 2.72:1 gears. Perfect for trail riding, but not nearly low enough for technical crawling

Rig 3: Samurai with 5spd, stock 3.73 diff gears, and 6.5:1 TC gears. 1st gear was SUPER slow technical crawling. 5th gear was fast enough for most ‘fast’ trail riding. The TC had twin sticks so I could easily flip to high range if I needed to go faster than 5th gear low range. If I was in 'Send it mode', I would regularly launch hills in 3rd or 4th gear. I could easily start out in 3rd gear from a dead stop. I loved this setup and never felt a need for anything more/different. I think you rode with me in this rig for a while at the Flats many years ago.

Rig 4: Cab truck with C6 auto, and Atlas 4spd (2:1, 2.72:1, and 5.44:1). I liked using 2.72 ratio for general trail riding. I loved the 5.44 ratio for slow technical crawling.
 
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CLRracer said:
You probably can't bolt up an Atlas crawl box. They probably have more integration between the two cases, I would imagine similar to how the Magnum and Titan replace internal parts of a 205.

Duane
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I was saying if you had the atlas bolted to an aw4, my example, I don't see why you could not bolt a NWF in front of it. Of course new drive shafts etc. I'm sure the atlas 4 speed is more than just a crawl box added to it.
drkelly said:
I’ve mostly wheeled four rigs, and I think the desire/want of TC gearing depends on auto or manual transmission.

Rig 1: 76 GMC Jimmy with TH350 auto and NP203 with 2:1 gears. SUCKED

Rig 2: Full size Bronco with C6 auto and NP208 TC with 2.72:1 gears. Perfect for trail riding, but not nearly low enough for technical crawling

Rig 3: Samurai with 5spd, stock 3.73 diff gears, and 6.5:1 TC gears. 1st gear was SUPER slow technical crawling. 5th gear was fast enough for most ‘fast’ trail riding. The TC had twin sticks so I could easily flip to high range if I needed to go faster than 5th gear high range. If I was in 'Send it mode', I would regularly launch hills in 3rd or 4th gear. I could easily start out in 3rd gear from a dead stop. I loved this setup and never felt a need for anything more/different. I think you rode with me in this rig for a while at the Flats many years ago.

Rig 4: Cab truck with C6 auto, and Atlas 4spd (2:1, 2.72:1, and 5.44:1). I liked using 2.72 ratio for general trail riding. I loved the 5.44 ratio for slow technical crawling.
Click to expand...
Rig 4 is what I want to have. 2:1 and 2:71:1 seem like the perfect combo of low ranges.
 
ghost said:
I was saying if you had the atlas bolted to an aw4, my example, I don't see why you could not bolt a NWF in front of it. Of course new drive shafts etc. I'm sure the atlas 4 speed is more than just a crawl box added to it.
Click to expand...

You can, NWF even offers a shorter underdrive that works specifically with the Atlas. But apparently you can't just turn a 2spd Atlas into a 4spd Atlas using only Atlas parts. Your original comment about it being "sales bs" led me to believe you thought Atlas was just saying that in order to up sale a 4spd. If that's not what you meant, then my apologies.

ghost said:
Rig 4 is what I want to have. 2:1 and 2:71:1 seem like the perfect combo of low ranges.
Click to expand...

This is my plan too. Sometimes I feel like 2.72 is too low for just trail riding in my application, but I think 2:1 would be just right.

Duane
 
ProbablyBroke said:
This is all great feedback. I just fear that with the 5.0 I’ll have 3 useable gears. Crawl, bump it and party mode.
AA states that there are differences between a 2 and 4 speed beyond just the 2.72 planetary housing. Tech man said you can’t just bolt up a crawl box .
Click to expand...
Correct. Kinda.

A 4spd Atlas is similar to the shortest NWF box. Meaning the output of the planetary goes directly into the input of the atlas. It essentially replaces it. Same for the atlas 4spd.

So you can’t just remove an underdrive box off the front of a 4spd atlas and run it like a 2spd.

Also the front of the 4spd case isn’t machined for the normal 6 bolt round pattern it’s machined to fit the underdrive box.

When I talked to AA they didn’t want to sell me the stuff needed to convert my 2spd to a 4spd as it technically doesn’t exist in the way you would think,

Which is what led me to find the shortest NWF box that will bolt directly to the front of my 2sp and replace the atlas input itself, keeping it short.

Sorry for hijacking, I guess my point I ended up at, it’s not worth it to me to sell my 2sp atlas just to get the atlas 4sp when I can just use NWF stuff on a 2sp atlas.

TLDR: The 4spd atlas and underdrive is not a “doubler” or crawl box setup in conventional thinking. It is very similar but not identical to NWF shorty box and atlas 2spd or other config.

Fwiw in my jeep. 4.7/ax15/d300 4:1 5.38s. I’m always in 2nd and 3rd gear. 1st gear I use for rack gardens and the like but isn’t actually low enough to crawl like a comp buggy and is too low for anything practical. 2nd gear gets it done and 3rd gear is party mode. I used to sometimes use 4th gear for big party mode with non sticky’s but it was just too brutal. With the 39” reds vs 42” dots I never use 4th anymore in low range, 3rd gear party mode is more than sufficient @ 30:1 ratio. 2nd gear I’m 50:1 so I’d shoot for that that range is optimum. Anything that is beyond that range and can split that range helps widen the best effective range.
 
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Ah I see what you are saying. I didn't realize they were saying the 4 speed is that different. My main point was if you get a 2 speed you should be able to make it 4 with any underdrive.
 
Here's my set up, and I have never had any after thoughts. 5.7 throttle body engine, Turbo 350 trans, Atlas 4 speed, 1:1, 2.73:1, 3.8:1 and 10.34:1. One tons, stock 4.56 gears, Detroit's front and rear, 43 stickies. In places I can drive the road, I used my highest gear, inside a park, just getting to the tr4ails, I use the 2.72, on most all of the trails, I run the 3.8, for those really steep hill descents I will run the 10.34, so I can actually raise the RPM and drive down and not be sliding down, Some trails with a lot of technical stuff, I will try and crawl with my lowest gear For max control...the lowest gear, have to bump it, back to the 3.8. Hill climb an break traction, throw it in neutral, pull in the range box, and 10.34 backing down, no brakes, just throttle, and control. Bottom line, I love my combination.
 
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