Dana 30

So I read on Pirate that a CJ 30 is (aside from the ring gear) basically the same as a Dana 44. If true, this would more or less make it completely pointless for me to swap. They said there are versions which use the larger U-joints but those are the closed knuckle type. Is there any truth to this?

 

Well I know that CJ Dana 30 knuckles and outer shafts will bolt to a Scout II Dana 44. IIRC the Scout Dana 44 is the small u-joint version. Not sure on closed axle Dana 30's.

 

You can put aftermarket shafts witht he larger u-joints in a open knuckle CJ Dana 30. Its a tight fit but it can be done.
Here is mine with the larger u-joints.

 

I think the bearings and axle tubes are stronger in a 44 than a 30. The R&P is also bigger. I believe the misunderstanding comes from some of the stock 44's having the same outter shafts. But I can tell you, I have a D30 and a D44 and the 44 is much heaver and looks stronger than a 30.

All that being said, you can build a 30 to a fairly strong axle. But you can build a 44 stronger.

 

I also run alloy axles (33 spline Alloy USA to be exact) with the big joint kit. All my research says that with that mod, the D30 should hold up to the same use as a 44 except for shock loading the ring and pinion (for tires up to 35"). The D30 ring gears is a LOT smaller than a D44 ring gear and won't take the shock loads a D44 will. There are a lot of pictures on Pirate where people have ripped the teeth right off D30 gear sets.

 

Why do you need to upgrade? are you breaking parts or are you going to be doing some hardcore rock crawling? this will help determine if you need to upgrade and what to upgrade to. Dana30's are pretty durable axles depending on engine, lockers and skinny pedal usage.
Kevin

 

Yea, I figured as much. I found some specs for the axle tube thickness as well, check this out

Dana 30 2.5" x 0.250" wall

Dana 35 2.5" x 0.250" wall

Dana 44 1/2 ton 3.0" x 0.250" wall

GM 10-bolt 3.0" x 0.250" wall

GM 12-bolt 3.0" x 0.250" wall

Ford 9-inch 3.0" x 0.250" wall

Dana 60 rear 3.125" x 0.313" wall

Dana 44 front 3/4 ton 2.75" x 0.500" wall

Dana 60 front 3.125" x 0.500" wall

Dana 70 rear 3.625" x 0.563" wall

Odd since I always "heard" that the 44 had a thicker housing. Maybe everyone meant the 3/4 ton version?

Kevin, I don't really need to upgrade as I'm only running 31's at the moment. But in about a month I'm going to start building my own frame, so I was considering an upgrade.

 

There's a 44 and a 44HD. The J-20s use the 44HD on the front axle. I presume that's what they are pointing to as a 3/4 ton 44.

The 30 has different tube thicknesses too. Supposedly, around 1976 the 30 tube thickness was increased. Don't know how much it helps though - all the ones I've seen with a broken housing (carrier) have cracked the pumpkin where the tubes go in. I expect these were broken by jumping. Gears and u-joints in a 30 should be a much higher liability for most drivers, from what I've seen.

 

I think I'll just convert to the larger U-joints and get some alloy shafts then. The weight savings and ground clearance is more valuable to me than a negligible gain in strength. My build is based on 35's which shouldn't be a problem, I'm not big on showing off.

 

Also if the 30 tubes got thicker around 76 wouldn't the diameter also increase? My research indicates they are the same diameter.

 

You can reinforce the housing and put larger axles in a 30 but the fact remains that you're still stuck with the small R&P. People on various forums have said that a 30 can be built as strong as a 44. That is simply not true and as aalison said, You can build a 44 even stronger.

 

Inside diameter is smaller -> thicker.

 

Really? But the 30 is a full floater, so the unit bearings are smaller? Weird. In any case it seems that the 30 would be a better choice as long as the RP holds up, but I imagine that a cryo'd set would cure this. I wonder why the 44 is so popular then, it's advantages are limited. I hear also that you can get 44 shafts that fit the 30 as well. so it looks like:

Clearance-30
weight-30
cost-30
axle tubes-same
U-joints-depends on model
R&P-44
axle shafts-44 (1.16 vs 1.31) Unless you upgrade the 30 axles

The 44 can be built stronger for sure but I bet that would be REAL pricey..Swapping seems like a waste of time.

 

When I looked at the attached photo of the axle tube diameters I learned something. I have a 44/60 8 lug combo out of a J truck. I always looked at the thickness of the tubes and wondered how folks were bending the tubes, etc. Now I see there is a .25 wall and a .5 wall. I have the .5 wall. Now I know............

But if I were going to put money in an axle, I'd start with a 44 or a 60. Unless I was going to stay with a 33's or under. Then I'd stay with the D30. But over 33's, I go to a D44. Over 40 inchers, I'd go to a D60.

But then again, a lot of people run D30's for years without any issues.........

 

Agreed. If I swapped id just go directly to a 60.

 

I see people talking about shaft strength, ring and drive pinion strength, tube thickness, etc. Few people are talking about carrier bearing size, carrier housing strength, diff case strength, side gear and diff pinion gear strength, pinion cross shaft strength, etc. You can't just look at upgrading one component or the size of that component, you have to look at the WHOLE picture and the whole diff. So you upgrade the shafts to cryo or alloy shafts with bigger joints. You still have 27 spline shafts unless you upgrade the diff. Ok, you've upgraded the diff to 30 spline for the stronger axles, in order to do that you have to have a diff case with thinner carrier bearing journals to accept the larger shafts. OOPS! Weak spot created. Ok, aftermarket diff case, maybe a Detroit locker or some other aftermarket locker that is strong enough in this area, still have small side gears, diff pinion gears, shafts, etc. Still have small ring and pinion, still have small diameter tubes, still have axle ends ("C" s) that have lighter castings than a larger differential. All these things are why many people upgrade to a 44. They don't need the weight or ground clearance loss or cost of a 60, so for those folks a 44's can really fit the bill where a 30 is not strong enough. Not everyone needs a 44 front, but for those where a 25, 27, or 30 just isn't strong enough, a 44 can be just right. Can it be expensive? You bet. but when needed it's better to spend the money up front to get a longer lasting, stronger diff than break all the time or spend a ton of money on a smaller axle that all you are doing is shifting the weak spot around.

 

I'm not arguing any of these points, but here's my reasoning for keeping the 30:

Bearing and housing failures don't show up on the radar. They may happen, but not often enough for people to commonly site them as reasons to NOT use a D30. Same with tube size/strength, inner and outer knuckles, wheel bearings, pinion bearings, pinion shaft. Again, I have no doubt many people have broken all of these parts, but the frequency is not high enough to make me worry about it. The high failure parts are the ring and pinion, axle shafts, and axle u-joints, and steering links, so this is where I concentrated my build efforts. An ARB locker replaces all of the differential parts and are proven to be bulletproof. I don't care about actuation problems for this discussion. Aftermarket axles are 31 or 33 spline (I don't remember off hand what mine are, I think 33), and the ARB to run these axles fits in the stock carrier bearing size. No loss of strength there. Aftermarket axles use D44 size u-joints, I use heavy duty cold forged joints, so I have elimnated that worry. I will be upgrading my steering linkage to DOM eventually if needed. I figure the weak points I still have are the outer knuckles (weak by my estimation), and the ring and pinion. Since I also have nothing to prove to anyone about my wheeling skills, I drive carefully and avoid overly stressing the axles at all times. Bouncing is hard on ring and pinions, I don't do it. I know I could go snap this thing at will, but it isn't built for extreme rock crawling. I'd have thrown in a D60 if that's what I wanted. For now, attentive, careful driving will alllow this thing to live forever.

Other reasons I stayed with the 30: Iit still uses stock wear and tear items I can easily find and replace. On the normal easy to medium trails in my area, I have no concern that I will not be able to drive home at the end of the day. It works with my "stockish" build plans and didn't require a ton of fabrication to make it fit. I feel that I have eliminated the weak spots that are common and easy to fix with the end result being a highly reliable axle with vastly improved performance.

 

Everything Nickmil said is right on the money. One other factor that is critical is how you drive. I've been running a D30 with 35" Krawlers for three seasons. I upgraded the axles to the large u-joint Alloy USA shafts and haven't had any problems since. I did break a stock u-joint snow wheeling one day. It was kind of a fluke though. I drove the Rubicon 3 times this summer, Fordyce once and Barrett Lake once so my Jeep gets used. Also with low enough gearing I don't have to thrash my way through the tough spots. With a new Powerlock and the axles and re-gearing I'm into the D30 for about $1,000. I doubt you could do a 44 for that.

 

Like I said in my post, not everyone needs a 44. If a 30 with some upgrades fits your bill, great! I was just pointing out some of the things that were hardly mentioned that many people don't think about and "why" some people upgrade to a 44, which was kind of a question that was asked.

 

Roger that, Nickmil. After re-thinking my figures, I've probably got more like $1,400 into my D30. If I had twice that much to spend, I'd have a 44 too.