• Welcome to ClassicBroncos! - You are currently viewing the forums as a GUEST. To take advantage of all the site features, please take a moment to register. It's fast, simple and absolutely free. So please join our community today!
    If you have problems registering or can't log into your account, please contact Admin.

Atlas II 3.8:1 with Dana 44 front axle

bgr

Joined
Nov 3, 2018
Messages
9
Loc.
Minneapolis
Hello. I imagine this has been brought up before and my search skills are shoddy, so I apologize if this has already been commented on.

I put in a NV4500 with an Atlas II (3.8:1 gearing) between a Dana 44 and a Ford 9". I'm uncertain what future path I'm going to take with the axles... but in the meantime... do I have any concerns with the 44 I should be aware of?

Appreciate any insight.
 

sykanr0ng

Bronco Guru
Joined
Aug 11, 2014
Messages
5,363
Tire size?
Differential gear ratio?
Engine?

Planned use of Bronco?
 
OP
OP
B

bgr

Joined
Nov 3, 2018
Messages
9
Loc.
Minneapolis
Tire Size is 33"
Differential gear ratios. The 44 is 3.54:1 and the 9 is 3.50:1
Engine is 302

I don't really have a planned use, and this is my first bronco build (that I'm doing myself) so I'm just figuring things out. Read that as... I'm an idiot; treat me like a child.
 

garberz

Bronco Influencer
Joined
Jun 24, 2007
Messages
6,861
Loc.
Conejo Valley, Ca.
To take advantage of the OD in the trans, you’ll want to re gear the axles. 4.56’s-5.38’s, depending on your tire size choice. 4.56’s for 33’s, 4.88’s for 35’s, 5.13’s for 37’s. Etc. But it’s kind of a sliding scale depending on use. Others will argue, I’m sure.

Mark
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
35,630
That axle gearing will be a poor match for the tires and engine. Once you start driving it you will find that out in short order. It will drive like a turd. Needing granny to get off the line. Overdrive useless unless going downhill, with a tail wind, hurricane force, on an 8% grade. The general rule of thumb is 4.11 gears are very well matched to 33" tires WITHOUT an overdrive transmission. For a stock 302 I would gear for about 2300 RPM at 60 MPH in overdrive. There are plenty of online calculators for figuring axle ratio off that.

Back to your axle question. The stock Dana 44 is pretty good. There is one weak point that you may run into. The axle U-joints are a little too small. If you put power to them, in a tight turn, expect them to pop. Now there are all kinds of high dollar options out there. But for only a 33" tire you can do very well with a set of factory large U-joint shafts. Go from the 260 size to the 297 size. They are very good shafts. And filled with genuine Spicer U-joints they are very stout. 15 years ago I got a pair from Randy at Driven Auto Parts (local here in AZ) and I beat on them for years. Hard AZ trails. Front locker. Things like front digs on hard ground. Put the back corner of the rear bumper against a rock and throttle in reverse for a reverse bumper pivot. They held up to that stupid stuff. Only when I won a set of aftermarket U-joints did I ever end up doing upgrades beyond stock parts. Just don't run parts store grade U-joints, when they fail it will take out both the inner and outer shafts. Only run the Spicers. The short side is generally a match for the square body chevy Dana 44 short side. The long side needs a custom cut and spline, no off the shelf shaft fits. Driven knows what will work. This is the most affordable upgrade that will hold up to your tire size.

You can always run stock until it blows up and upgrade after. I made it into my second trip with low gears and sticky fresh 33s before I blew up the stock U-joint wheeling 400 miles away.
 
OP
OP
B

bgr

Joined
Nov 3, 2018
Messages
9
Loc.
Minneapolis
I appreciate the advice on the ratios. I didn't expect it to be the most efficient ride near-term, but as long as I'm not going to hurt the transfer case in the meantime I'm happy.

I've been looking at Currie and Spicer for the axles. Open to suggestions for 302 replacement options. I have 35s ready to go. Since it's relatively cheap I may regear the differentials to find the right combo before I splurge on something fancy.
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
35,630
I appreciate the advice on the ratios. I didn't expect it to be the most efficient ride near-term, but as long as I'm not going to hurt the transfer case in the meantime I'm happy.

I've been looking at Currie and Spicer for the axles. Open to suggestions for 302 replacement options. I have 35s ready to go. Since it's relatively cheap I may regear the differentials to find the right combo before I splurge on something fancy.

If you are going to test gearing, don't do both differentials then test drive. Do just the rear. If you don't like it you only need to regear the simple 9". Pretty simple and cheap. At least compared to doing both axles. Only down side, you can't go wheeling with horribly mismatched gears. They will bind too badly.
 

garberz

Bronco Influencer
Joined
Jun 24, 2007
Messages
6,861
Loc.
Conejo Valley, Ca.
I appreciate the advice on the ratios. I didn't expect it to be the most efficient ride near-term, but as long as I'm not going to hurt the transfer case in the meantime I'm happy.

I've been looking at Currie and Spicer for the axles. Open to suggestions for 302 replacement options. I have 35s ready to go. Since it's relatively cheap I may regear the differentials to find the right combo before I splurge on something fancy.

35’s, start with 4.88:1 gearing. If you have dreams of going up to 37’s, 5.13’s work fine with 35’s too.

Mark
 

Nothing Special

Sr. Member
Joined
Nov 25, 2016
Messages
839
As a data point, I have 33s, 4.10s and an NV3550 5 speed overdrive. Personally I like the gearing, but I also understand why others would say it's too tall. I can start in 2nd if I'm not in a hurry, but with any load, or if I want to get into the power soon I need to start in 1st (but with the NV3550 that's not really a problem, it's not a granny gear). And I can let it loaf in OD at about 35 mph as long as I'm not looking to accelerate. It'll cruise easily in OD at 55 with decent acceleration, but if I'm towing and going up a hill I'll be down in 4th at 55.

4.35 gears (if they existed) with 35s would give the same gearing as my 4.10s and 33s. Similarly 4.60 would be the same with 37s.

I'm not telling you what you should use, just letting you know how my setup works. You can decide if you like it or want lower gearing (higher numbers) like most people suggest.
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
49,244
And that's good to know. Because one aspect of the Dana axles (and many others I'm sure) that the Ford 9" does not have, is that as the gear ratios go down (numerically higher) the strength goes down too.
The pinion gear gets smaller and smaller as the numbers climb.

So no matter what you choose, remember that if you think you can get away with a lower number, that might be the way to go.
It's an unfortunate relationship, as the tire size goes up you certainly want lower gearing. But as tire size goes up, you want more strength too!

So as with most things related to old Broncos, it's a dance and balancing act.

Paul
 

okorangebrnco

Bronco Guru
Joined
Nov 25, 2004
Messages
1,661
I've had an Atlas II and NV4500 in my bronco since 2005. I am geared at 4.56 with 35's and cruise down the highway around 1900-2100. I have never calculated the speed, but I know I am keeping up with traffic. I can tell you 5th gear is useless unless I am cruising down the highway, but it does get decent fuel mileage for a brick.
 
OP
OP
B

bgr

Joined
Nov 3, 2018
Messages
9
Loc.
Minneapolis
Thanks for all of the helpful feedback. After spending some time on it, it appears I can go pretty tall. 5.86:1 is looking like the right fit. Having my rear diff blow up in the last couple days is also forcing my hand here. If I was to go in the direction of an ATK 302 and wanted to consider Dana 60 front and rear which products should I be looking at?
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
35,630
I would cringe a little at 5.86 gearing. The pinion is getting pretty small at that point. Loosing a good bit of strength with that gear package. Thankfully the 302 isn't typically a huge powerhouse, but I would still back off the gearing just a little bit. 5.38 would be a bit stronger and you would never notice that little difference in gearing.
 
OP
OP
B

bgr

Joined
Nov 3, 2018
Messages
9
Loc.
Minneapolis
Maybe I should stop hanging out with hot rod guys.

What about lockers? I work with a former Eaton guy who has been recommending their e-locker daily. Is it ARB vs Eaton vs ?
 

sykanr0ng

Bronco Guru
Joined
Aug 11, 2014
Messages
5,363
Maybe I should stop hanging out with hot rod guys.

What about lockers? I work with a former Eaton guy who has been recommending their e-locker daily. Is it ARB vs Eaton vs ?

I am a much bigger fan of the Eaton Truetrac.

Most of those who choose a selectable locker here seem to prefer the ARB.
 

nvrstuk

Contributor
Just a Bronco driver for over 50 yrs!
Joined
Jul 31, 2001
Messages
9,384
Loc.
PNW
Ton of options...

Here's a tip. Find a fellow Bronco owner who has a different gear/tire combo setup than you and drive his or her rig.

I know of one semi-local Bronco Club that actually has a club outing where guys drive each other's rigs so they can see what different spring shock combo's ride like. Different wheel/tire/gearing combinations do to power, what an OD feels like trying to climb a hill with a 302, etc.

This is the absolute BEST way to find out what works for you without doing it the way I and many others have...by changing all of the above over the decades...it gets expensive LOL
 

bchesley

Full Member
Joined
Dec 21, 2012
Messages
327
I have the E-locker and love it. Flip of a switch and its instant traction. No leaky lines or compressors to deal with. I only wish they made one for the 9".
 

Nothing Special

Sr. Member
Joined
Nov 25, 2016
Messages
839
Thanks for all of the helpful feedback. After spending some time on it, it appears I can go pretty tall. 5.86:1 is looking like the right fit....

For what it's worth, 5.86 gears are typically called "deep" or "low". Something like 3.08:1 would be "tall" or "high".

Think of it like tires. Tall tires bring engine rpm down at a given speed, low tires bring engine rpm up. Or like transmission gears. 1st gear ("low gear") brings engine rpm up, 3rd (or 4th, or 5th, or 9th - "high gear") brings engine rpm down. same for axle gears. "Low gears" (high numbers, like 5.86) bring engine rpm up, "high gears" (low numbers, like 3.08) bring engine rpm down.
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
49,244
This is all a very interesting turn you're taking in (seemingly to us anyway) mid-stride.
First, you don't know what you ultimately want to do with the truck, so can't really make an informed decision and should be cautious or you're going to end up doing at least some of what you change all over again.

I don't know about the others, but I assumed you were not even driving it since it sounded like you were in mid-swap with an NV4500 and an Atlas. Apparently you're driving it though, as you just said you blew up the rear differential. Doing what I might ask? And is this still with a stock 302?
Maybe the 3.50's and 33's were just too mis-matched for your driving style? Or do you think there was something wrong inside the diff already that just finally let go?

And not long into this conversation you're still not sure what you want to do with the rig, but are thinking of dropping in dual Dana 60's? Man, you've got a lot going on!
At least at one level, if your current use is putting enough stress on things to bust up a 9" diff, then a Dana 60 swap is actually making some sense for both ends.

After spending some time on it, it appears I can go pretty tall. 5.86:1 is looking like the right fit.

The right fit for what though? The 35" tires you've got, or something bigger? And what kind of driving? We still don't know what you will spend most of your time doing.
With 35's, that's a good off-road gear, but leaves a lot to be desired on the highway. How much time do you think you'll spend out on the road? That combo will put your engine at approx. 2500rpm at 60mph and 2900 at 70.
That's actually pretty good for power and crawling, especially with a 302, but is a bit high if you prefer lower rpm running.
With the 38" tires you should drop approx. 200rpm from that.

So that's your target. Which side of that do you want to run? Do you know what rpm range your next engine will be happy at? You going to make it carbureted or EFIed

Having my rear diff blow up in the last couple days is also forcing my hand here.

You've totally got us curious! What happened?
But you're right, it is a serendipitous occurence for someone that was contemplating gear changes.

If I was to go in the direction of an ATK 302 and wanted to consider Dana 60 front and rear which products should I be looking at?

Not up on my current Dana 60 lore, But Dynatrac, Currie, and probably a few others, including Dana themselves in fact, will make you a very wicked combination.

Maybe I should stop hanging out with hot rod guys.

Maybe! But it sounds like they're your crowd too. Maybe mostly still? Or at least have been hanging around them longer.
Are you hot-rodding your Bronco?

Maybe it's not that you have to stop hanging with one or the other group (even though I know that statement was probably facetious) but that you are going to need to interpret what you hear from each group and, taking it all into account and mulling it over, make your own decision based on what you like.

What about lockers? I work with a former Eaton guy who has been recommending their e-locker daily.

Love the e-Locker, but don't really have any experience with them. ARB is even more proven than Eaton when it comes to selectable lockers (just longer making them) but I'd trust either one.
Frankly though, if I had the choice it would be the Eaton all the way just from a plumbing aspect.
With the e-Locker you have a switch and some wires. Period.
With the ARB you have the switches, the valves, the compressor, the tubing all to keep safe too. I just think wires are simpler.

Is it ARB vs Eaton vs ?

Yes, there are others. And given the choice I prefer a set-it-and-forget-it style like the Eaton Trutrac that was mentioned already. But my wants and needs don't include many of the things you're already going. So maybe a selectable is the best way. Detroit Lockers would be suitable, but are not my favorite and can still break like just about anything else.

You're obviously putting the fun-money into this rig so that it will be able to do just about any fun thing you choose to do. But are you really going to go rock crawling with it? Sand dune jumping? Mall crawling and cars-n-coffee showing with bragging rights? Heck, even drag racing?!;D;)

I still think you should narrow down your expectations and desires to the most desirable. Unless you really do want to do it all. In which case you are on the right track already.
That includes lower gearing than you normally need, because it makes it easier with big tires to go crawling and accelerating from a stop. Heavier duty axles and diffs because of the big tires and powerful engine. Bigger engine because of all the added weight and rolling you're adding.

Which brings me to the next question. Do you really want a 302? Even a built one? Or should you be contemplating a stroked 351 derivative at this point?
You won't "need" it for 35's of course, but if your honest assessment of your desire has you going bigger next time, you would do well to think of a bigger engine for more torque at lower rpms.
And more ability to break the next thing!:cool:;)

It's that big rabbit hole leering up at you.%)
Good luck with the repelling gear!;D

Paul
 
OP
OP
B

bgr

Joined
Nov 3, 2018
Messages
9
Loc.
Minneapolis
Haven’t had much time to dig in but looks like the spider gears. There are pieces in there. Everything was looking good and then it wasn’t. This happened after about 30 minutes of driving. Nothing out of the ordinary. I bought this thing from someone who was trying to flip it. Body is in good shape but everything else was a disaster so I picked it up intending to swap out the whole drivetrain. I have a few friends who know a lot about certain parts of vehicles but I have very little mechanic experience myself and spend most of my time reading about how to do things. For the most part it hasn’t been too frustrating. I have more difficulty understanding terminology used which I’m unfamiliar with so I end up down the rabbits hole at times.

Plans. I really don’t have any plan. I might just sell this one when I’m done with it and start over. It’s a great learning process for me as the only other rebuild I’ve done was a 66 vette (327). That was tilted much more towards cosmetic stuff. I was pretty young when I used to gofer with my father when he worked on his vehicles. He passed back in 2003 and now that I have kids I’ve been working on recreating his garage. 66 corvette, 71 bronco, 68 chevelle, 73 pinto wagon (we’ll see about this one). I think I would like to take any of my kids who have interest as they get older on a couple trips. Like trans America , Mojave’s rd, and maybe some of the more advanced stuff.

So. I’m thinking I might try my hand at rebuilding the rear to get this rolling again. Then shop for some 60s and new driveshafts and all the accoutrements. My research is pointing me to keeping a 302 in here but I’m not certain. I’ve been looking at other options. In the end I will put 35s on this most likely. But unlikely larger than that. I have a fitech efi 4 — I got this from someone who pulled it off their mustang. I’m really more of a carb fan. But I might use it if I ever decided to use this for a daily driver. Sometimes it’s tough to keep the carb on the vette in the zone up here in the north when the calendar turns.

So far... so good though. I really do appreciate such thoughtful responses here. Great community you have.
 
Last edited:
Top