Gearing/trans questions

[BroncoManSam]

To get your crawl ratio, you multiply the lowest gear ratios in each piece.

6.69 (NP435) x 1.96 (NP203) x 1.96 (NP205) x 4.56 (Diff ratios) = 117:1. This combo works for a lot of folks. I think 162:1 (Bluntly put) is stupid low. So there's the formula ^^^ You can insert the numbers from whatever combo you want.

Concerning the 203/205, it's gonna weigh about 6000lbs (maybe some over exaggeration there, it's all cast iron cases) when compared to the aluminum cases of the NWF parts and the Atlas case--just something to consider.

My dad wheels Hot Springs ORV park last weekend with NP435, Dana 20 and 3.50 gears on 35" tires aired down to about 10psi. the only real problems he had was the limited slip in the front. If it'd been a full locker, he' probably never would've had an issue. Also, his tires are just old out of date BGF ATs with no grip. So that combo gives him 6.69 x 2.36 x 3.5 = 55:1. He's pretty happy with the ratio. He only complains about the lack of a front locker and the poor pavement manners of Grizzly in the rear. It shifts the main drive from one rear tire to the other seemingly every time his shifts a gear or turns a corner. For mainly offroad it's a good choice tho.

Thanks for the formula. I suppose 162:1 is really low, but it wouldn’t have to be in the lowest gearing the whole time because of the twin stick transfer case and the ability to shift the underdrive from high to low. I’m leaning towards the NP205 with the Titan underdrive, but I also like the sound of the NP205/203 doubler as well, especially because it’s potentially much cheaper. At any rate, both set ups are cheaper than the Atlas, and the NP205 with the Titan weighs less than the 205/203 doubler. So now it’s between the doubler set up, and the 205 with the Titan. Decisions decisions... thanks for all the info!


Sent from my iPhone using Tapatalk

 

[nvrstuk]

Gearing is very personal. Many on this list seem to never want to have to shift down going up a hill on a County road.

Like Paul mentioned earlier. You will be so low geared for the trail you could run almost any highway gears. (maybe I added a little)

Engine power/torque choice and whether you don't mind shifting on a hill greatly determines diff ratios.

Also, will you EVER increase tire size? If there's a chance you ever will, then go with steeper gears.

I was extremely pleased with 4.56 gears with 37" tires and 351W. Also ran ZF/203/D20 so I had to shift out of OD on hills... got 14.5mpg on 2,000 mile trips..

Soooo many options... have fun!

 

[nvrstuk]

What carb?

Trails and rocks essentially means two proven choices before most went efi- stock 2bbl or Qjet. I had to go SEFI because I couldnt w/o major expense (like SEFI for a 600hp stroker wasnt a few additional dollars) but I couldn't have the fuel psi and the float bowls set low enough for extreme off camber AND still supply enough fuel for throttle down wheeling with the stroker.

Qjet works great until you want the extreme "best of both worlds" scenario.

I've built dozens of qjets for off camber. Great throttle reaponse because of the small primaries and when dialed in easily attain 14+ mpg with 35"s and 351W on the highway at 65-70.

Tire choice makes a difference for mpg tol.

 

[BroncoManSam]

What carb?

Trails and rocks essentially means two proven choices before most went efi- stock 2bbl or Qjet. I had to go SEFI because I couldnt w/o major expense (like SEFI for a 600hp stroker wasnt a few additional dollars) but I couldn't have the fuel psi and the float bowls set low enough for extreme off camber AND still supply enough fuel for throttle down wheeling with the stroker.

Qjet works great until you want the extreme "best of both worlds" scenario.

I've built dozens of qjets for off camber. Great throttle reaponse because of the small primaries and when dialed in easily attain 14+ mpg with 35"s and 351W on the highway at 65-70.

Tire choice makes a difference for mpg tol.

I’m running a Holley Street Warrior 600 cfm 4160, and currently I have 35x12x15r tires, might go to 37’s later. I’m not super concerned with gas mileage. I think in the future I may swap to an off-road Avenger by Holley, or maybe even EFI, but I really don’t want to go to EFI. Time will tell though, my mindset could change.


Sent from my iPhone using Tapatalk

 

[nvrstuk]

I've weighed EVERYTHING!! Don't let some internet rumor about D60's weighing hundreds of lbs more than a D44 or a rumor that a 205 weighs 100 more lbs than an Atlas keep ya from doing what you want/need to do.

Nobody mentions or says a thing when they swap an Atlas for a little D20 (appr 30#) but people come out of the woodwork when talking about 205s weighing a hundred lbs more than an Atlas...which they dont. NP205 weighs 30lbs more than an Atlas...

Nobody screams about the weight of a 6r80 auto replacing a C4 or the 120 more lbs a ZF weigjs over the stock 3 spd RAT?
My 6r weighs 213 lbs and now that I've tuned it and can use it in full manual shift mode or 4 different auto programs, Id never go back to any other trans. Its about 150# more than a stock 3 spd.. lol
Don't care.

The 203 by the way weighs 38 more lbs than the Titan.

Also remember that this extra 30lbs for a 205 is down low keeping your COG low. Guys running 5.5" susp lifts have lifted all those gearboxes, engines etc up raising the COG.

 

[BroncoManSam]

I've weighed EVERYTHING!! Don't let some internet rumor about D60's weighing hundreds of lbs more than a D44 or a rumor that a 205 weighs 100 more lbs than an Atlas keep ya from doing what you want/need to do.

Nobody mentions or says a thing when they swap an Atlas for a little D20 (appr 30#) but people come out of the woodwork when talking about 205s weighing a hundred lbs more than an Atlas...which they dont. NP205 weighs 30lbs more than an Atlas...

Nobody screams about the weight of a 6r80 auto replacing a C4 or the 120 more lbs a ZF weigjs over the stock 3 spd RAT?
My 6r weighs 213 lbs and now that I've tuned it and can use it in full manual shift mode or 4 different auto programs, Id never go back to any other trans. Its about 150# more than a stock 3 spd.. lol
Don't care.

The 203 by the way weighs 38 more lbs than the Titan.

Also remember that this extra 30lbs for a 205 is down low keeping your COG low. Guys running 5.5" susp lifts have lifted all those gearboxes, engines etc up raising the COG.

Good point for sure, thanks for the info. I didn’t think about the COG, that’s also a good point. Doesn’t make my decision any easier unfortunately haha. I definitely like the idea of the 205/203 setup being much cheaper, but I also still like the Titan/205 idea too.


Sent from my iPhone using Tapatalk

 

[nvrstuk]

My .02 this afternoon says don't let anybody talk you out of a doubler!! Doesnt matter if it's a ZF with deep geared Atlas or whatever. Without a doubler you either have deep low gears or you dont. Nothing in between.
Like crawling on top of snow at 200:1 or up a waterfall at 200:1‐ great. Works perfect for that. But you cant run higher mph up a sand dune, tbrough the mud or in deep heavy wet snow when your t-case is straight 1:1 ratio (w/o stupid amounts of HP) OR a 4.3 ratio which won't allow enough wheel speed for mud, sand or heavy, deep, wet snow.

Keep your options open.

A wheeling buddy of mine just pulled his 203 and replaced it with the Titan-because he wanted to. . I had a Titan for my 205 and sold it to another local guy.

I love weighing out all the options, writing down the pros and cons of each part and combination... did this for the first 40 yrs with this Bronco and always went strongest/cheapest.

 

[BroncoManSam]

My .02 this afternoon says don't let anybody talk you out of a doubler!! Doesnt matter if it's a ZF with deep geared Atlas or whatever. Without a doubler you either have deep low gears or you dont. Nothing in between.
Like crawling on top of snow at 200:1 or up a waterfall at 200:1‐ great. Works perfect for that. But you cant run higher mph up a sand dune, tbrough the mud or in deep heavy wet snow when your t-case is straight 1:1 ratio (w/o stupid amounts of HP) OR a 4.3 ratio which won't allow enough wheel speed for mud, sand or heavy, deep, wet snow.

Keep your options open.

A wheeling buddy of mine just pulled his 203 and replaced it with the Titan-because he wanted to. . I had a Titan for my 205 and sold it to another local guy.

I love weighing out all the options, writing down the pros and cons of each part and combination... did this for the first 40 yrs with this Bronco and always went strongest/cheapest.

That makes good sense, maybe the doubler is what I want then. I think I was talking myself out of a doubler haha, but after looking at some other setups, it’s not as bad as I originally thought. Thanks for your info and .02 (worth more than that in my opinion). I suppose with the doubler I can still have a ratio higher than 100:1, and that’s plenty low. I’ll just have to source a 203 in addition to the 205, I’ve already found an adapter kit online. I also just calculated my final ratio with the NP435 and doubler, and it’s 119.59:1.


Sent from my iPhone using Tapatalk

 

[nvrstuk]

There is a 203/205 adapter on line that is not highly rated... there are a couple extremely highly rated. Stay away from the one.

 

[BroncoManSam]

There is a 203/205 adapter on line that is not highly rated... there are a couple extremely highly rated. Stay away from the one.

The ones I’m looking at now are from Northwest Fabworks and Offroad Design. I imagine the offroad design one is slightly better, as they are a well-known brand, but the Northwest Fabworks one looks pretty good too.


Sent from my iPhone using Tapatalk

 

[brewchief]

I think if I was in your situation I would have to look hard at one of the planetary boxes and a 205, 203/205 doubler is good but it only gives 2 low ranges, the lower geared planetary box would give a 3rd option.
To me there is nothing worse then always being in the wrong gear, the more options you have the easier it is to find the right gear.

The low geared atlas cases are great until you don't want to go that slow or are doing something that requires more wheel speed, I watched several jeep Rubicons struggle at the sand dunes a couple weeks ago, they didn't have enough power in high range and couldn't get enough wheel speed in low.

435/205 combo was pretty common in 70s trucks and broncos, bellhousing will probably be wrong as most of those were FE engines or 351m/400.

Sent from my SM-T510 using Tapatalk

 

[BroncoManSam]

I think if I was in your situation I would have to look hard at one of the planetary boxes and a 205, 203/205 doubler is good but it only gives 2 low ranges, the lower geared planetary box would give a 3rd option.
To me there is nothing worse then always being in the wrong gear, the more options you have the easier it is to find the right gear.

The low geared atlas cases are great until you don't want to go that slow or are doing something that requires more wheel speed, I watched several jeep Rubicons struggle at the sand dunes a couple weeks ago, they didn't have enough power in high range and couldn't get enough wheel speed in low.

Sent from my SM-T510 using Tapatalk

That was my thinking in the beginning when I was looking at the BlackBox Titan. Someone mentioned my wheel speed would still be slower even if I left the transfer case in high, and the underdrive unit in high, which makes sense I suppose, but I’m not sure how that would be different from the doubler, other than being lower geared, because the doubler would have 3 sticks just like the twin stick 205+BlackBox underdrive.


Sent from my iPhone using Tapatalk

 

[BroncoManSam]

I think if I was in your situation I would have to look hard at one of the planetary boxes and a 205, 203/205 doubler is good but it only gives 2 low ranges, the lower geared planetary box would give a 3rd option.
To me there is nothing worse then always being in the wrong gear, the more options you have the easier it is to find the right gear.

The low geared atlas cases are great until you don't want to go that slow or are doing something that requires more wheel speed, I watched several jeep Rubicons struggle at the sand dunes a couple weeks ago, they didn't have enough power in high range and couldn't get enough wheel speed in low.

435/205 combo was pretty common in 70s trucks and broncos, bellhousing will probably be wrong as most of those were FE engines or 351m/400.

Sent from my SM-T510 using Tapatalk

What bellhousing will I need then?


Sent from my iPhone using Tapatalk

 

[brewchief]

What bellhousing will I need then?


Sent from my iPhone using Tapatalk

The stock bell used in 3 speed broncos works fine with the 435, some of the newer truck ones from a straight 6 or small block truck will work as well.

Sent from my SM-T510 using Tapatalk

 

[BroncoManSam]

The stock bell used in 3 speed broncos works fine with the 435, some of the newer truck ones from a straight 6 or small block truck will work as well.

Sent from my SM-T510 using Tapatalk

Oh ok, I must’ve misunderstood the other comment about bellhousings, thanks.


Sent from my iPhone using Tapatalk

 

[gremlin]

I run c4 with marlin crawler box with 5.0 gears to a j shift 20 456 gears and 35" tires. I drive it daily plus rock crawl, mud or snow. lots of choices in the final ratio I can run.

 

[jamesroney]

Well, here we go...
You haven’t answered some key questions that will make a difference.
1. How do you drive?
2. How long will you keep your Bronco?
3. What do you want to have break when you break it?

Here’s my Blackbox integrated into a 205. It is as short as it can get. It gets long.

 

[BroncoManSam]

Well, here we go...
You haven’t answered some key questions that will make a difference.
1. How do you drive?
2. How long will you keep your Bronco?
3. What do you want to have break when you break it?

Here’s my Blackbox integrated into a 205. It is as short as it can get. It gets long.

I’d say I don’t drive hard, but I don’t have a ton of wheeling experience. I plan to keep my Bronco forever, as long as I live. And for breakage, I guess things that I can afford to break and replace easily. Thanks for the picture. What’s the length of your front and rear driveshafts with the 205/Titan combo?


Sent from my iPhone using Tapatalk

 

[jamesroney]

I might be the wrong person to ask. I break stuff. Pretty much everything gets broken, twisted, or bent. But my driving strategy is based on brute strength, ignorance, and momentum. I run 1310 CV driveshafts, and hope that they break first.

My rear driveshaft is currently 30 inches and the front is 26. Rear axle is a high pinion Dana 60 front is low pinion 44. Suspension Lift is 3.5 inches over stock. I’m running an NV4500 and a Dana 20 today. When I swap to the 205/black box, it will move things back by 7 inches.

 

[BroncoManSam]

I might be the wrong person to ask. I break stuff. Pretty much everything gets broken, twisted, or bent. But my driving strategy is based on brute strength, ignorance, and momentum. I run 1310 CV driveshafts, and hope that they break first.

My rear driveshaft is currently 30 inches and the front is 26. Rear axle is a high pinion Dana 60 front is low pinion 44. Suspension Lift is 3.5 inches over stock. I’m running an NV4500 and a Dana 20 today. When I swap to the 205/black box, it will move things back by 7 inches.

Thanks for your detailed information, I appreciate it. Another guy is sending me the measurements of a 205/203 doubler setup in an EB, so I’ll compare those numbers to yours, and see which one fits better. My guess is the 205/Titan will fit better and take up less space. Regardless of which one I choose, I imagine I’ll have to shorten my driveshafts. Let me know when/if you swap in the 205/Titan, and how it goes.


Sent from my iPhone using Tapatalk