What's going to break when you add HP & Torque?

[Yeller]

IMO I have no preference on gear supplier. Some are a little quieter than others and some ratios are quieter than others. For you prescribed use I’d bypass any locker and go with a Truetrac, which I see you selected.

 

[nvrstuk]

I hope you’ve got the Atlas 2 transfer case. The input shaft on the Atlas 4 is not chromoly and is at risk with a high-torque engine when the planetary is engaged. The Atlas 2 gets the same input shaft, but since there’s no planetary it will see 1/3 of the torque. But if you’re not really wheeling it you’re probably fine either way. Also, the Atlas 4 would give you a difficult driveline angle.

I’m in a similar situation. I’m building a 630 hp engine, and I’m going to wheel it for a couple of years before adding a 14 bolt rear end. With the bad history nvrstuk had with his 35 spline ARB rear locker I’m going to install the competition ARB (RD99CE). This adds $1K to my axle, but will give me peace of mind. I’m not sure how strong the other lockers are, so I can’t comment there. I’m going to sell my whole rear end in a couple of years and recover some of the expense.

Can't go 14 bolt now? Save a TON of money doing it once? Just asking.

 

[Mascasa]

Back in my HP289/271 solid lifter days with my 3 spd, L70x15 tires I never ate a ujoint, never had pinion rotation issues (stock springs), never grenaded an output shaft and I would literally eat 28 spline axles when shifting on pavement.

This was decades ago but I remember twisting off over eight, 28 spline axles and just always drove home in fwd. That only lasted till '85 because that's when I built my 351W and 200,000 miles later I never ate another 28 spline till it twisted off 31 spline axles because of low gearing crawling up stuff with doublers, 6+:1 first gear, 37"s, lockers, etc. Torque would just twist stuff off at low speed.

All history now...

BTW, I have a spare, brand new 9" Nodular housing w/Daytona pinion support for sale.

If you can swing it go with a 14 bolt full floater in the rear and a WFO Concepts torque arm and 1350 u joints. That will handle lots of power and if you were to break an axle you won’t be screwed.

 

[nvrstuk]

Heck if I know...... I'm a 61 year old Bronco rookie. How would I identify what I have. Does my OEM (MARI) build sheet tell me that answer or do I need to get pics for our experts to continue guiding me?

BTW....thanks to everyone that's helping me. Truly appreciated.

If I go with the 31 spline option, will my existing stock housing work? That is a cheaper option for sure if the 35 drives me to a new housing. At some point I have to start minimizing my project cost & scope creep. I tend to go all in for the best, but often good enough works.

Well, you asked and I've been known to give my opinion out (even when not asked).

So-

I gotta ask... if this build is for the street only then save THOU$AND$ by not buying an Atlas. IMO from knowing only what I've read here, there is absolutely no need/use for an Atlas. You want something that is super strong and looks purdy???? Then powder coat an NP 205 case and once again, save thou$and$ by not buying something that is not needed.

OK, you have a 4:1 first gear in your 6l auto correct?

You have a torque converter (and you know you get about 2:1 gear reduction through a good converter right)

You have truckloads of torque off idle

You have little to no use/need for low rock crawling gears for 4 wheel drive with your 4:1 first gear and TC

You need something that will handle ANY & ALL abuse you can and want to dish out

You want to save some cash

If you add all this up the 205 does all this at a $2,000 dollar savings- at least.

Can you tell us why a 205 won't work for you?

Seems so obvious by what I know of your build I should have mentioned it earlier.

... and going with a 205 is not "giving up" anything, it's the wisest decision you could make so you can spend that $2,000 + dollars somewhere else

 

[nvrstuk]

I hope you’ve got the Atlas 2 transfer case. The input shaft on the Atlas 4 is not chromoly and is at risk with a high-torque engine when the planetary is engaged. The Atlas 2 gets the same input shaft, but since there’s no planetary it will see 1/3 of the torque. But if you’re not really wheeling it you’re probably fine either way. Also, the Atlas 4 would give you a difficult driveline angle.

I’m in a similar situation. I’m building a 630 hp engine, and I’m going to wheel it for a couple of years before adding a 14 bolt rear end. With the bad history nvrstuk had with his 35 spline ARB rear locker I’m going to install the competition ARB (RD99CE). This adds $1K to my axle, but will give me peace of mind. I’m not sure how strong the other lockers are, so I can’t comment there. I’m going to sell my whole rear end in a couple of years and recover some of the expense.

Me and LOT's of other builds with gobs of torque were destroying 35 spline ARB's. Yes, some were due to the design of the engagement dogs inside and inappropriate application & tiiming of air supply engagement but there is not much meat inside a 35 spline ARB so the comp model IMO is the only way to go. Also 3 different ARB guys that I know from early, early ARB days that go waaaaay back with ARB confirmed what I just said. I would never run another 35 spline non-comp model with 40" or larger tires in severe applications knowing what I learned.

 

[hossbronco]

Don’t tempt me. I just want to get this rolling and if I go full-width in the rear I’ll have to do it in the front. I was hoping to find the path of least resistance before I go crazy on my axles (in the future).

But I guess for the price of a third member I could find a Dana 60 to keep that spot warm for my 609. It would be cheaper but take me longer. Decisions.

 

[nvrstuk]

Here I go again (sorry if this is against the grain of your build but...)

I'm with Steve again, go 14 bolt and NEVER look back. No upgrades needed.

Buy a used housing.

Buy gears, carrrier, install kit and a TruTrac

Keep a similar WMS by going with dually hubs or the ones I built are close.

BAM, potentially a thou$and or more saved again as I really doubt your stock 9" housing isn't bent, needs straightening and a truss to keep it from bending again.

This saves a TON of money, gets your axle upgrade so you won't be worried about ever buying another one, shave it so it's within 1/4" of what a 9" measures off the ground and also gets you a FF which for me is a HUGE safety concern with the poorly designed retainging ring to keep your axle from sliding out. Great lightweight setup for cars but not for EB's or pickups.

 

[nvrstuk]

Don’t tempt me. I just want to get this rolling and if I go full-width in the rear I’ll have to do it in the front. I was hoping to find the path of least resistance before I go crazy on my axles (in the future).

But I guess for the price of a third member I could find a Dana 60 to keep that spot warm for my 609. It would be cheaper but take me longer. Decisions.

lol

Don't go full width- I didn't, had no use for it- like rocknhorse. We can't use them up here in a few spots still.

Easy to narrow the 14 bolt up with the hub selection and different widths of the axles in the boneyards. So cheap and easy and you will only do it once- unlike me who was a slow learner. I could have saved building several rear ends- heck, I don't even want to list all the down time and repairs I had over the decades (since '76) with trying to make a 9" as strong as everyone said they were (joke). Strong for a car but not for the abuse we put them through.

Steve was the final straw as I'd been hearing it for a long time, had one sitting in my shop, sold it, yada, yada, yada.

Should have done it and the HP60 back at the end of last century. Would have had a LOT more time to do stuff around the farm instead of rebuilding another grenaded 9". lol

 

[WPS 73 Bronco]

Well, you asked and I've been known to give my opinion out (even when not asked).

So-

I gotta ask... if this build is for the street only then save THOU$AND$ by not buying an Atlas. IMO from knowing only what I've read here, there is absolutely no need/use for an Atlas. You want something that is super strong and looks purdy???? Then powder coat an NP 205 case and once again, save thou$and$ by not buying something that is not needed.

OK, you have a 4:1 first gear in your 6l auto correct?

You have a torque converter (and you know you get about 2:1 gear reduction through a good converter right)

You have truckloads of torque off idle

You have little to no use/need for low rock crawling gears for 4 wheel drive with your 4:1 first gear and TC

You need something that will handle ANY & ALL abuse you can and want to dish out

You want to save some cash

If you add all this up the 205 does all this at a $2,000 dollar savings- at least.

Can you tell us why a 205 won't work for you?

Seems so obvious by what I know of your build I should have mentioned it earlier.

... and going with a 205 is not "giving up" anything, it's the wisest decision you could make so you can spend that $2,000 + dollars somewhere else

Regarding the Atlas decision, you missed that conversation 6 weeks ago on my LS build thread. I had reached out to Novak and Advanced adapters and they only had one suggestion, an Atlas. I found another Transfer Case builder who told me to go with a GM NP241 with a short yoke. The 205 never really came up in discussions with these guys because of the HP concern.

When I brought it to the forum, the 241 was shot down due to length and width as it was 3” wider that my D20 creating more driveline angle issues. Atlas was the hands down recommendation. In the discussion the 205 briefly came up as an option, but it never gained much attention.

It’s too late for that consideration at this point as the Atlas shipped on Tuesday.

Now back to the rear end….. I got lost a bit between the responses to my needs and Hossbronco’s Regarding the 14 bolt rear end Vs goin with my 9”, 31 spline WH 3rd member, 1350 yoke, and 31 spline axles. How do I save thousands $ by going to the 14? My current cost is coming up to about $2500 including the axle wrap.

Let the debate continue as I haven’t made a purchase yet. Options
1) 31 Spline with existing 9”……. $2500
2) 35 Spline with new large bearing 9”…….$3500
3) 14 Bolt housing with what internals and where to I buy?…….$ TBD

 

[nvrstuk]

Save thousands on the 205. It's stronger than anything out there that fits, except the brand new Atlas.

You would save "tons" of money on the 14 bolt. No truss needed either.

$3500 compared to the parts I listed in my last post. I am late for an appt but will check in later.

Just good options. I got my last two housings for under $100 each. Shaved them and bought the new cover for $120. gears and locker isn't very spendy

 

[rocknhorse76]

Save thousands on the 205. It's stronger than anything out there that fits, except the brand new Atlas.

You would save "tons" of money on the 14 bolt. No truss needed either.

$3500 compared to the parts I listed in my last post. I am late for an appt but will check in later.

Just good options. I got my last two housings for under $100 each. Shaved them and bought the new cover for $120. gears and locker isn't very spendy

Agreed! The 205 is a beast. They used them in monster trucks for gosh sakes! I have the Blackbox Titan (thanks for selling that to me brand new!) and a 205 behind my 408W and 4R70W, and I hardly ever use anything but the “pathetic” 1.96:1 low range in the 205. And mind you, folks, I snow wheel (or at least attempt to) with NVRSTK, so I sometimes have to beat on my rig to keep up lol. And the 14B is pretty much a no-brainer too. Cheaper to build than a 9” and there is no comparison when it comes to strength. You get a better pinion angle to boot! I narrowed mine 4” just by using dually hubs.

 

[1969]

I’m in the 14 bolt/Sterling camp. I’d never spend money building the 9” when you can source those rear axles and they will easily live with your HP. I put super duty axles and a 205 in my rig because they were cheaper to start with than upgrading any of the bronco parts and once upgraded there is no comparison to the stock bronco stuff. Even if you don’t want to source a junkyard 14 bolt you can go to east coast gear supply and they will build a 14 bolt to your specs and ship it to your door.

 

[WPS 73 Bronco]

I found a local shop that builds rear ends and other stuff. I'll drop by there and check him out.

 

[WPS 73 Bronco]

I found this one that's local. Could this be a good starting point. I could take it to a local shop to rebuild.

 

[nvrstuk]

What rocknhorse and 1969 said. Just can't go wrong with the 3/4t & 1t parts when building a rig that is no longer a 1/4t model with 27" tires with 3.5 gears, no 100% positive lockers, etc. Great little rig when first built but when you triple the torque (some engine but mostly gearing) running thru to the rear you need the drivetrain to be rated at "triple" also.

Check your WMS on what you are designing for your vehicle, then go to the 14 bolt Bible on Pirate (or my thread it is linked) and has various WMS mearsurements listed and determine what you want/need. Then buy the rear you want. Heck, Steve probably remembers all those WMS #'s in his head, he's done a hundred more than I have.

All I know is I tried for 30 yrs (edit: actually 40+ yrs since the first twisted 28 spline axle) to keep the 9" alive with the "best" parts and even then it grenaded. I mean a fabbed housing, TruHi 9", custom 35 spline RCV axles, custom RCV FF hubs, 35 spline ARB, inner axle seals so the troublesome TruHi9 would be bathed in oil even sitting on a side hill and it still won't take it. Go stock 14 bolt (shave it) and don't worry.

 

[nvrstuk]

https://classicbroncos.com/forums/t...-thread-shaved-15-bolt-ring-gear-turn.297561/

Here's some info on widths, hubs, 9" fab vrs 14 bolt weights (17 lbs more), etc

Post #93 from above:
"
This measurement is so hard to believe I checked it 2 different times...

The center of the 14 bolt pinion shaft is only 1 1/2" lower than the pinion shaft on the TrueHi9! I really thought the pinion on the 14 bolt would sit several inches below the axle centerline but because it is tilted at such an angle to point towards the t-case it ends up being less than 2" difference height off the ground (or above the axle centerline) btw these 2 rear ends.

Another measurement that really surprises me is my "914" (current 9" w/14 bolt hubs) only sits 1 1/2" higher off the ground than the new 14 bolt! Which means when I shave 1 1/4" off with the 13 bolt cover I lose less than 1/4" of ground clearance with the 14 bolt... never would have thought it would be that insignificant!"

 

[WPS 73 Bronco]

So another curve ball on rear end options, and I’m more confused. The 14 bolt option clearly has more strength, but it doesn’t look anything like a simple mod and a bolt in option. Following your thread, there seems to be lots of fab required work plus a lot of knowledge required to support the fab work. It also looks like this is overkill for my needs.

Earlier responses felt like for street cruising the 31 spline option worked fine.

Am I reading this right, or am I missing something.

 

[Yeller]

You’re really not far off, but let me put this out there, a stock new f150 has 34 spline axles, a huge pinion shaft, and huge bearings. Ford didn’t spend money on that stuff for nothing. So is the 31 spline 9” adequate? Maybe, maybe not. I try to look at what OEM’s did in similar applications of power and or weight, I believe that once you get to 33” tires or beyond with HP is where the trouble begins, even stock f150’s come with 33” tires (275/60-20 is 33”) and use a much more robust rear axle that is nearing sterling capacity, today’s 8.8 is not the 8.8 of old.

As for simple install, it’s not terrible, just needs shock mounts and spring perches. I’d be looking for a “ a cab and chassis” 14 bolt, it has a 63” WMS (wheel mount surface) width, a regular one is 67”.

Please don’t take any of us telling you what to do, even those that sound pushy with strong opinions have scattered enough high end, expensive “unbreakable” parts scattered like dust in the wind. So we’ve literally spent $10’s of thousands on rear axle components and wound up with a basically stock 1 ton rear end that we spent way less on and is living a long happy life. 14 bolt just happens to be widely available, affordable, and the least expensive to build. It’s one of those trying to encourage you to spend it once, spend it smart and never worry again.

Just a side note…. Ever seen what can happen to a bronco that breaks a rear axle at road speeds? Unfortunately it’s more common than we want to admit. I have a Dana 60 with Set20 bearings and 35 spline axles in one of my vehicles . If I was running larger tires it would be full float and probably should be now, those are the same as a 35 spline 9” and they break at the wheel flange, wheel falls off…..

 

[rocknhorse76]

So another curve ball on rear end options, and I’m more confused. The 14 bolt option clearly has more strength, but it doesn’t look anything like a simple mod and a bolt in option. Following your thread, there seems to be lots of fab required work plus a lot of knowledge required to support the fab work. It also looks like this is overkill for my needs.

Earlier responses felt like for street cruising the 31 spline option worked fine.

Am I reading this right, or am I missing something.

A 14-bolt is NOT overkill for 500hp and the fabrication involved is very minimal.

 

[nvrstuk]

Everything Steve said above about newer trucks, axle spline counts, shaft diameters, etc just re-affirms that the Bronco is a 1/4 ton rated vehicle and it shows. People ONLY think HP kills parts and they are SO FAR from the truth. It gets so tiresome replying to the same mindset. All of us responding to this post agree (I hope so by now).

Spring perches, shock mounts and you can literally slap/bolt a disc brake kit on and bolt it all up (minor things like ujoint straps/caps, etc) but it will be done once.

Caveat on my build. I am a nit-picker for doing things as cost concious and as strong as I can afford and need. My willingness to look at numbers, data, whether I need to make .250" spacer rings so I can use a hub not designed to fit on a 14 bolt axle but make it fit because it makes my WMS .500" narrower then I'll spend a week to do it. You don't have to. Get a C&C rear, swap the gears and carrier to your ratio and locker of choice, bolt on a disc brake kit and slide it under your Bronco. You WILL NEED to move the spring pads on whatever 9" axle you buy anyway because your engine/trans/t-case is a different length than stock and it's imperative that your pinion angle is correct.

SO comparing it to a 9" install you are essentially welding on shock mounts and a couple other little items. It really is that simple (unless I forgot something obvious)!

Like rocknhorse said, a 14 bolt is not overkill and minimal fab work.