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Gear Reducer or....

Montoya

Sr. Member
Joined
Feb 22, 2007
Messages
518
So I've been running an NP205 and I like the fact that it's bulletproof and even in the event of a failure...it's always cheap to fix. I wish there were lower gears available but so far I haven't found anything for the Ford box which leads me to a planetary box. I've looked at the three main ones; The Black Box, Magnum Box, and Strong Box and found they are all similar with the Black Box from Northwest Fab looking like the more premium option.

My question is simple, should I go with a reducer box or bite the bullet and go full Atlas? I like the option of having basically two low ranges but is it worth the added weight and complexity over a standard 2 speed atlas?

When I option out the Black Box with the heavy duty input shaft and the triple cable shifters it's around $2400 but I can probably sell my rebuilt NP205 for a couple hundred and get into an Atlas for about even money. The Atlas comes with a shifter standard, weighs less, is shorter, and has the reputation of being pretty well built but that's why I pose the question to the experts on here...what would you do?

Lastly, is there an advantage of one over the other in packaging under the bronco? From my searches, it looks like the Atlas can be squeezed between the frame rails but may require moving the engine over a smidge. I know my NP205 would require a major frame notch if I want it tucked up...that said, good luck breaking the case on an NP205 so tucking it out of the way is only for ground clearance and not for TC life.
 

Nothing Special

Sr. Member
Joined
Nov 25, 2016
Messages
804
I wouldn't consider myself an expert, but I do have a little experience. I decided on an Atlas 4.3 and have been happy with that choice. My biggest concern with that low of a low range was finding myself wanting something between low range and high range. At least so far that hasn't been an issue. With my NV3550 I have just enough overlap between low range/5th gear and high range/1st gear that it's pretty tolerable. And the Atlas shifts really well, so when I do need to switch ranges it's not bad either. Obviously there is some benefit to the dual case route. But I'm glad I went the way I did rather than having the weight and complexity of dual cases.
 

BUCKWILD

Full Member
Joined
Jun 20, 2016
Messages
350
Loc.
Butte county
the atlas dose not have the strength of the 205. I have broke a few atlases but yet to break a 205. That being said just how hard do you beat on it? if not hard an atlas will be fine. the trail hero is an option i think its a little stronger.
 

Boss Hugg

Contributor
Bronco Guru
Joined
Jun 8, 2010
Messages
2,140
Being one who likes to prepare for all situations, I'd prefer a doubler.

I'll also recommend doing your research on the strong box and it's manufacturer. Pirate4x4 is a good place to start that.

I haven't seen the Magnum until just now. I think for that much money, I'd go ahead and mortgage the house and go with a four speed atlas. And by doing the 4 speed atlas, you can start with a 2.72 low (more comparable with the d20 gearing than 1.96 in the 205) and then add whatever ratio to back that up. I think this would give more options.

And now that I look at it, can someone tell me why AA isn't selling separately the planetary box that they put on the atlas?? If you're building it, why not sell as many as you can?
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,835
I didn't wee what transmission you are running.

The thing about adding another box is weight and length. Not really the weight of the doubler, but the added leverage from the 205 sitting even further back. You have to all but abandon the original transmission mount and put something about where the doubler mates to the 205. You are supporting the ball of reduction and using the transmission to stabilize it.

And the length. Looks like you have a high 9 so not that much of a worry. But for anyone else you will be running out of driveshaft length.

The Atlas has evolved over the years. I looked at one last year and one that was about 10 years old. There has been slow evolution over that time to make improvements. With the abuse they get in competition, I doubt you will ever brake one in a trail rig. I remember the old one when there was an upgrade option for the shaft size on the yokes, I think by now it is no longer an option, you just get the good stuff.
 
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Montoya

Sr. Member
Joined
Feb 22, 2007
Messages
518
I didn't wee what transmission you are running.

Good catch, I should mention I'm running a ZF. My motor makes about 600HP at the crank (522 wheel hp, 570ft-lbs) and I plan on adding bunches more. I'm also hard on the throttle but relatively smart about when I hammer on it... Relatively... My wife would argue this point.
 

sprdv1

Contributor
REBEL
Joined
Mar 8, 2007
Messages
81,734
if you can afford it, just go atlas and be done w/it.. Just different bracing to take into account
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,835
A ZF has enough gear spacing that an Atlas makes sense. Overdrive in low range counters a lot of the low gearing. You don't have the holes in the gearing that a little double fills in.
 
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Montoya

Sr. Member
Joined
Feb 22, 2007
Messages
518
A ZF has enough gear spacing that an Atlas makes sense. Overdrive in low range counters a lot of the low gearing. You don't have the holes in the gearing that a little double fills in.

This is why I go to the experts. The whole time I was thinking reducer but the price kept turning me back to the Atlas.

What ratio Atlas do most go with? Is it worth the extra $ for the 5.0:1 or just stick with the 4.3:1.

Also, what tail housing would be best for a ZF with a high pinion 9" in back? Will a standard tail with a speedo provision work ok or should I go short to be safe?

Lastly, what U-joint should I use? I have 1350's on both axles but 1410's or 1480's are available for the TC. In my mind I want the weak joint on the rear to be at the axle to avoid a pogo-stick incident in the event of a failure but maybe I'm over thinking it.
 

Boss Hugg

Contributor
Bronco Guru
Joined
Jun 8, 2010
Messages
2,140
I've been looking at a spreadsheet with different combinations of ratios... for the ZF, I'd recommend an atlas with a 3:1 ratio, or a D20 with Teralow gears and HD output.
 

Apogee

Contributor
Bronco Guru
Joined
Nov 26, 2005
Messages
6,033
What ratio Atlas do most go with? Is it worth the extra $ for the 5.0:1 or just stick with the 4.3:1.

I picked up a used ATLAS 3.8:1 box, which I plan on putting behind my NV4500. If you have a manual transmission with a granny gear, or an auto/torque converter, the really deep 2-speed T-case gears like 5.0:1 create some big gaps between high and low-range. For most all-purpose rigs, I like the 3.0/3.8:1 options...but I'd run a 4.3:1 as well as I know a lot of guys have run them and like them for the most part. FWIW, I'll have a final drive ratio of 117:1 in low range. With a 4.3:1 box, that would be closer to 130:1, but either way, there's a decent overlap between high and low range.

Otherwise, I'd get a 4-speed box or doubler/205 to cover those gaps is you want to ability to get way up into the deep gear ratios. My brother has a Marlin ultimate crawler case in his Toyota with an automatic, and in low-low, it's ridiculously slow and will twist the truck up on itself with his Vortec 4.3 V6 and 4L60E trans. Other than messing around, he basically never uses low-low range.

You could also consider the Trailworthy Fab Hero boxes if money isn't an issue...not sure how well one would fit between the frame rails on an EB, but somebody needs to be the guinea pig, right? :cool:
 

KyleQ

Bronco Guru
Joined
Apr 24, 2008
Messages
5,480
Atlas is the way to go - very few are actually able to break them and I've been trying to kill mine going on ten years. With that kind of power you won't have to go super deep - but then again it entirely depends on your driving style and terrain.
 

Nothing Special

Sr. Member
Joined
Nov 25, 2016
Messages
804
.... What ratio Atlas do most go with? Is it worth the extra $ for the 5.0:1 or just stick with the 4.3:1....

.... If you have a manual transmission with a granny gear, or an auto/torque converter, the really deep 2-speed T-case gears like 5.0:1 create some big gaps between high and low-range....

I believe the ZF has a 5.72:1 1st and a 0.76:1 OD. So with a 5.0:1 Atlas, OD/low range would be 3.8:1, well above 1st gear/high range. It's still lower than 2nd gear/high (2.94:1) so there's not much overlap, but it's not going to give gaps.

Like I said above, I find the overlap with a 4.3 Atlas and NV3550 pretty good. My 1st gear is 4.01:1 and OD is 0.78:1. So OD/low is 3.35:1. Similar kind of overlap to a 5.0 Atlas with a ZF. So I'd think you'd find the overlap OK. Is it worth it? That I can't help you with.
 

BUCKWILD

Full Member
Joined
Jun 20, 2016
Messages
350
Loc.
Butte county
3.0-3.8 is as low as i would go 4.3 is deep unless you like to crawl in 3rd and 4th i like my doubler 203/205 the 4.0 to one with both and a c6 is good in the snow but thats about the only tine i use it in the rocks i only use the 205
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,835
1 gear of overlap works, but usually you want more. With the power you have on tap the 5:1 just doesn't feel right. Not sure of your driving style but I would feel a 3.8 or 4.3 would be a better match. You can still get a reasonable trail cruising speed in low range. It can really suck to spend the whole day shifting in and out of low range for every 30' rough patch you want it for.

As for U-joints. 1350s are going to be tiny for that much gearing/power. 1410, is a good one. I know nothing about 1480s. I would think 1410 should be sufficiently strong so long as you can keep the angles good. I have been amazed at what a 1310 can take if not put into a bind.
 

bmc69

Contributor
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Jun 11, 2004
Messages
11,852
My motor makes about 600HP at the crank (522 wheel hp, 570ft-lbs) and I plan on adding bunches more. .

Good lort!! :eek: What the heck you running??

FWIW, some years back I built a 408 that was 342HP/496ft-lbs on engine dyno and then eventually put it on a chassis dyno with the 39.5 tires on the truck. The driveline/tire losses were on the order of 25% and more.
 
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Montoya

Sr. Member
Joined
Feb 22, 2007
Messages
518
Good lort!! :eek: What the heck you running??

FWIW, some years back I built a 408 that was 342HP/496ft-lbs on engine dyno and then eventually put it on a chassis dyno with the 39.5 tires on the truck. The driveline/tire losses were on the order of 25% and more.

Ha, yeah I built the motor first before I did anything else and I mean anything... Manual steering, 35" tires, four wheel drums, stock 3 speed, Dana 20 with a mild 3.5" lift (on it when I got it). Needless to say, it was a handful!

It's a bored and stroked 351, now 427, fully ported aluminum Edelbrock heads, full roller conversion with 1.7 rockers and custom grind cam (aggressive lift but don't remember the number right now), girdled bottom end, sequential fuel injection, AEM stand alone ecu, GM LS individual coils, and long tube headers. I run methanol injection and 10.9:1 compression with the current pistons.

I dyno'd it on a Mustang chassis Dyno in Carson CA (basically sea level) in the old configuration and I'm estimating close to 600hp at the crank assuming loses. I expect a large decrease in power at the wheels now with 37's, the ZF, np205, hi9, and beefier driveshaft. If I add the Atlas, that might be even more.

I have a pair of 42mm Garrett gtx turbos sitting in a box on my shelf and I'm thinking of fabing a pair of turbo headers for it and making however much power I want up to around 900. Bottom end would take it if I throw in lower compression dished pistons made for boost.

We used to build 1700hp Acura 3.0l v6's 12 years ago so 900 from a huge V8 with turbos these days isn't too hard. I want to run the truck as is and get the new suspension dialed in first before I get crazy.
 

Apogee

Contributor
Bronco Guru
Joined
Nov 26, 2005
Messages
6,033
I think you passed crazy a few gas stations ago ;)

...and I like it.
 
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