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Old December 13th, 2005, 09:38
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D-30 Axle FAQ

Dana 30 FAQ


I know I have a Dana 30 front axle, which version do I have, and how can I upgrade it?


Disconnect 30:

This axle uses a vacuum actuator on the passenger side to slide a locking collar between an intermediate shaft and an outer shaft. This feature keeps the driveshaft from spinning on the highway, thereby yielding a vibe free ride. This axle came with 260 sized u-joints (more on that later), and 27 spline shafts, just like all other Dana 30s. You can use a 95 Wrangler ABS shaft to upgrade this axle to 297/760 joints and keep the disconnect feature. Dana part numbers for this are 75589-1x for the right side and 75815-1x for the left. You can also upgrade to 297/760s with late model non-disconnect shafts by using any TJ or XJ shafts from 95 and up vehicles, but you will need to order a seal from your local parts store in order to seal the diff, since the old seal used to ride on the disconnect portion of the outer shaft.. The CR seal number is 11771, and can be purchased from any parts store for around 7$. The weak link of the disconnect axle is rarely the U-joint once it is upgraded to 297/760 size. The intermediate shaft is fairly short in these applications, and it has a large spline section where the actuator rides. This design makes the shaft excessively torsionally stiff, causing it to break the splines on the differential side. The broken part usually sticks in the diff, forcing a complete disassembly on the trail. This axle is a reverse spiral unit, commonly called hi-pinion or reverse cut (more on this below).

Non-Disconnect, RS:

This axle first made its appearance in early XJs with the advent of the Select-Trac t-case. It does not use a disconnect, so the front driveshaft spins even in 2wd. The early axles came with 260 u-joints or an interesting CV design that tends to be somehwhat fragile. Sometime in the mid-90s, the switch was made to 297/760 joints. Identical to the disconnect 30, it uses a 7.5 ring gear and 27 spline axles, and is a reverse spiral unit. Max gearing available is 4.88. Differentials and axle shafts are available to upgrade any Dana 30 to 30 spline, but a word of caution, when used in the rocks with aftermarket U-joints (more on this later), the weak link with this setup becomes the ring and pinion. This has to do with the inherent problem with the Dana 30 when used with big tires and low gearing, housing flex. When you apply torque to a pinion shaft, it tries to force the ring gear away from itself, and causing the pinion to ride up the gear teeth of the ring gear. This torque loading flexes the carrier and the housing unless both are stiff enough to resist it. With the Dana 30, the carrier takes a lot of abuse, which is why we see a lot of the 3 piece ARB carriers with broken and backed-out bolts. Eventually all this torque will weaken the ring gear and break teeth off of it or the pinion. Another weak link of this and later axles is the passenger side UCA mount. They fold like a cheap suit when abused. Do yourself a favor and weld a reinforcement plate to the front.

Non-disconnect, Low Pinion 30:

This axle made its debut, much to the chagrin of enthusiasts, in 2000. This axle uses geometry common to rear axles. The pinion rides below the ring gear centerline, and when used in a rear application, rides on the drive side of the gear. However, when used in a front application, the pinion rides on the coast side of the gear when driving forward. The coast side of a gear set has a greater slope to it than the drive side, so this accentuates our problem of ring gear deflection described above. When driving on the coast side of a gear, the ring and pinion is about 25% weaker than when running on the drive side. A reverse spiral gear as found in earlier XJ axles solved this problem by cutting the ring gear with the drive and coast side of the gear swapped. This design was conceived by Dana and Ford in the late 60s to improve driveline angles and strength in their front axles. It does both well. In a sense, the 2000 and 2001 model axles are a de-evolution in technology. They do, however, all come with 297/760 joints.


How can I tell which U-joint I have in my 30, and are there upgrades available?


There are three common sizes of U-joints in light truck applications: the ton 260 joint which uses a 1.063 diameter cap, a ton 297/760 joint which uses a 1.188 diameter cap and correspondingly larger trunion (the part that the cap rides on), and the 1 ton 332 joint which is a Dana 60 joint. The 297/760 is a strong and popular upgrade for the 260. All of these are made by Spicer corp. Lately, a slew of aftermarket joints have become available in the 297/760 size. OX, CTM, Jantz, Longfield, etc are all making joints which in one way or another increase the strength of the units. All have benefits and weaknesses, but most replace the needle bearings in the caps with bushings. This allows an increase in trunion diameter and a corresponding increase in strength. The downside is that the joints may see increased wear when driven in a vehicle that does not have hubs that unlock.

These joints should be used in high strength axle shafts such as a Warn or Superior. They can be used in an OEM shaft, but the ears of these shafts are fairly soft, and routinely rip off of shafts when using even OEM 760 joints. If you use these joints in any shaft, you must use a full circle clip to retain the cap. As axleshafts stretch, especially OEM Spicer shafts, they allow the cap to loosen and walk its way around. Eventually the little half-clip that retains them falls out and the joint is expelled from the shaft with extreme prejudice. Running a full-circle clip on an OEM shaft requires some clearancing of the shaft ears to allow room for the clip.

OEM Spicer shafts are like condoms. You use them once and then you flush them. The axleshaft itself rarely survives a U-joint break intact, as the four ears usually collide at a high rate of speed deforming them beyond recognition. Sometimes, though, you may think to yourself Self, I could get a new joint in there. That Crash guy is off his rocker. Trust me, the shaft is a goner, as it will usually be stretched and stress fractured. You may be limp it off the trail, but replace it ASAP. This is why Ive never hesitated welding caps in, they are a permanent installation anyway. Unless you like using your condoms twice.

Two more words on shaft breaks. If you hear the dreaded Snap, Crackle, Pop. STOP RIGHT WHERE YOU ARE. If you drive even 5 feet on a broken u-joint, you run the risk of the shafts riding up on each other and popping the ball joints out of their sockets. If you dont have a spare shaft with you, and you need to move, you may be tempted to pull just the outer shaft out. DONT DO THIS ON A D-30. The Dana 30 used in TJs/XJs/ZJs/MJs/WJs is not a full floating axle, that is, the shaft itself plays a role in carrying the weight of the vehicle. With the shaft removed, the bearings will fall apart, leaving you wheel-less.


Do all brakes and hubs interchange on Dana 30s?


Basically, there are three rotor/hub/knuckle combinations. The early style that MOSTLY came on disconnect housings, the late style that came on non-disco housings, and the latest style that came on low pinion housings.

The early style brakes can be identified by the 7mm allen-head studs that retain the caliper to a two-piece knuckle. These are generally specd on 84-90 vehicles.

The two later style uses a standard headed bolt to retain the caliper to a one piece knuckle.

The only difference in the two styles is the spacing, but it means you cant mix and match rotors from the various styles. Axle shaft lengths are the same, so you can plug in late model shafts into your early housing with no problem. Also, if you want to use the late model hub/rotor/knuckle combo, you can bolt them to your early housing without trouble.


How big a tire can I run on my 30?


This is where I know Im going to catch some flack. I am not a very big believer in the Dana 30 for rock use. I have seen a lot of broken shafts and carriers to prove it. So, I cannot recommend running a tire larger than 33 inches with a locker in the rocks. Larger than this, and several things become very apparent. Your braking ability becomes horrible, the unit bearings really begin to suffer, the ring and pinion are screaming for mercy and you may start having ball joint troubles.

OK, so youve got some money in your 30 and want to keep it. Understandable. Whats the ultimate 30? If I had to keep a 30, and I wanted to run 35;s on it against my better judgement, Id build it this way.

Id start with an RS non-disco housing, beef up the passenger side UCA mount, run 4.56 gears, and an OX locker. Why the OX? Its been my experience that the OX billet steel cover does a very good job of increasing housing rigidity, and the lockers themselves are at least as stout as an ARB. I dont like any automatic locker for the 30 because of the extra stress that is put on the axle at all times when you are in 4wd. At least with a selectable locker you can leave it off until you need it and save the unit some wear and tear.

Next, Id run WJ Grand Cherokee outers so I could move the steering up to the drag link hole which is about 2 inches higher than the OEM XJ 30 arm. Id run a WJ outer from a right hand drive vehicle on the drivers side so I could run the tie rod up high as well. The WJ brakes are a no-brainer, twin piston calipers with beefy rotors improve performance tremendously. Id use the Warn 5 on 5.5 hub kit and have the rotors machined to fit. This would get me the desirable locking hubs so I could comfortably run a CTM joint in Warn or Superior axles. I think Id keep the 27 spline axles just so that the ring and pinion wouldnt be the weak link, but it would be hard to resist the 30 spline units.

Please understand that if you build a 30 as described above, you can build a Dana 44 for about the same money.

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