Building the Ultimate Dana 30

Story & Photos by Off-Road Adventures Staff
Stepping Up to 30-Splines with G2 and ARB. Trent McGee shows you how to do it.
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The Dana 30 front axle has been around for a very long time; they have been the standard front axle used under Jeeps since the early "70s, and a new generation of the Dana 30 continues to pull duty under the current Wrangler JK. Most drivetrain experts will agree that the Dana 30 is stronger than it really has a right to be; despite having a fairly small gearset and 27-spline axles that use small axle joints, they manage to stand up to a moderate amount of abuse as long as tire size doesn"t get too radical and power remains near stock levels. Even so, it"s fairly easy to break a Dana 30 once larger tires and lockers are thrown into the mix. The axleshafts in particular are one of the weakest links. Its bigger brother, the Dana 44, uses a bigger gearset and larger 30-spline axles that are better suited to taking abuse, but swapping in a Dana 44 front axle is a complicated affair with several different things demanding attention, which adds time and expense. Fortunately, there"s an easy way to upgrade the Dana 30 to make it nearly as strong as a Dana 44 without having to jump through a lot of hoops. All it takes is some specialized parts and a little elbow grease.
Last month we compared the rear AMC 20 to the Dana 44 and then highlighted everything needed to transform an AMC 20 into an axle that is arguably stronger than a stock 44. This month we"re going to turn our attention to the front Dana 30 on the same "84 Jeep CJ-7 and make some significant strength improvements to match the rear. As you will see, building the Ultimate Dana 30 isn"t that hard as long as you pick the right parts and take your time. Though the subject of this article is a CJ Dana 30, much of what we cover here applies to upgrading a YJ or TJ Dana 30 as well.


1. To build the Ultimate Dana 30, we turned to G2 Axle & Gear and ARB. The foundation for the upgrade is the G2 30-spline chromoly axleshafts, which offer a significant strength improvement over the stock 27-spline shafts. Upgrading to 30-spline aftermarket shafts also requires a matching 30-spline carrier. These carrier choices are limited, but fortunately an ARB is among them and is probably the best choice for a dual-purpose daily driver/weekend ‘wheeler. Since the gears in the front axle have seen a lot of miles in their 28 years, we chose to do a full rebuild using a high-quality G2 4.10 gearset and one of their master overhaul kits.

2. Aside from just an increase in spline count, the G2 30-spline shafts (top) are also significantly larger in diameter compared to the stock shafts (bottom). We measured 1.15” across the splines of the factory shaft compared to nearly 1.30” on the G2. This 0.15” difference seems minor at first, but an axleshaft"s strength increases exponentially as it increases in diameter. Plus, G2 shafts are made out of 4340 chromoly steel, which is a much higher grade alloy than typical factory shafts. If a 30-spline upgrade is outside of your budget, G2 also offers 27-spline chromoly shafts that will work with stock or aftermarket carriers while still offering more strength than stock due to the higher grade materials.

3. The weakest link in most front axles is the axle U-joint. The factory CJ shafts (top) use a small Spicer 260X joint. The G2 shafts upgrade to a much stronger Spicer 760X joint, which is the same joint used in most Dana 44s since the mid "70s. G2 also beefed up the yokes that go around the U-joint and machined the shafts to accept full circle snap rings, which do a much better job of retaining the U-joint caps that the C-clips that are typically supplied with the joints. The G2 shafts also ship fully assembled using genuine Dana Spicer joints, which is a nice touch.

4. Here"s a closer view of the full circle snap rings. These snap rings go all the way around the U-joint cap and hold it firmly in place. Most aftermarket shafts can accommodate snap rings, while factory replacement shafts must be machined to accept snap rings. This is another reason why investing in a set of quality aftermarket shafts is a good idea for even a moderate off-roader.

5. The ARB is a driver-selectable locker, meaning that it acts like an open differential until engaged by the driver. When actuated, it locks the axleshafts together like a spool and provides the extra traction needed for difficult terrain. This is accomplished via compressed air from a compressor that goes through a seal housing (arrow) on the differential. This housing routes air to a piston inside the differential case, which engages a clutch that locks the differential. Because of this arrangement, special carrier bearings are supplied with the ARB that must be used rather than the bearings supplied in the overhaul kit.

6. Even if you"re not upgrading to 30-spline axleshafts (which requires changing the carrier), keep in mind that Dana 30s have a carrier split between 3.54 and 3.73 gear ratios. This split means that 3.54 and higher (numerically lower) ratios use a different carrier than 3.73 and lower (numerically higher) ratios. In this case, the Jeep was equipped with 3.54 gears. So even if we were only swapping the gears to 4.10s, we would have had to invest in a new carrier. This is yet another excuse to step up to a locker when re-gearing!

7. Because the 30-spline axleshafts are larger in diameter than the originals, the axle seals are also different. To address this, the G2 kit includes new inner axle seals (right). The seal rides on the raised surface machined into the new axleshafts (arrow). If these seals ever need to be replaced in the future, make a note that they are the same seals used in a TJ Rubicon Dana 44 front axle.

8. After completely tearing down and cleaning the axlehousing, you can install the inner axleshaft seals. These are tricky to install and are easily damaged, so be careful. We used a large socket that fit snugly inside the seal and then gently tapped the seals into place. Make sure the seal is fully seated and is not crooked or you"ll have a leak. If they do leak, the whole axle has to be torn back apart in order to replace them!

9. Use only a proper shop press to press the bearings on the carrier and the pinion; don"t use a hammer. Make sure everything is clean and seated properly. Remember, the ARB uses special carrier bearings, and the side with the seal housing protrudes past the bearing, so be careful when pressing the bearing on that side.

10. Pay close attention to the arrangement and position of any baffles and oil slingers in the housing when changing gears. There were several different combinations used over the years and all of them are crucial for proper oiling. As a general rule of thumb, if it was there with the original setup, it should be there with the new one. In this case, the housing had a large slinger under the pinion head (shown) and also a smaller baffle positioned behind the inner pinion race. We accidentally destroyed the baffle during disassembly and the overhaul kit did not include a new one, so we had to source one from a local drivetrain shop.

11. The side-to-side position of the carrier is adjusted by using shims. The original carrier was shimmed under the carrier bearings, while the ARB requires shimming on the outside of the bearings using the special shims supplied with the locker. Pay close attention to how the shims and master shim are arranged, especially on the side with the seal housing. Improper shim position will lead to carrier bearing failure.

12. The procedure for setting up gears has been the subject of several books, so it is best to refer to one of them if you want a detailed description of how it"s done. One thing we"ve learned is to always start with the original shim setup and then adjust from there. We were impressed with the G2 gears; we were able to get a good pattern after only three or four tries. The ability to read a pattern is something that comes with experience, which is why it"s best to have someone who knows what they"re doing help you, or leave this part to the professionals.

13. After installing the carrier for the final time, carefully route the copper air line from the seal housing through the fitting that you drilled and tapped in the housing (we covered drilling and tapping last month). Be sure this line clears the ring gear and also does not rub against the carrier bearing cap or the axlehousing itself. Once this is done, it"s a simple matter of installing the inspection cover and buttoning everything up.

14. After all of this preparation, installing the axleshafts themselves is pretty simple. Be sure to transfer the dust shields (arrow) from the old axleshafts to the new ones and install new inner seals if the old ones are worn (new outer seals are not supplied). The larger axle joints are a tight fit going through the knuckles, so be sure the knuckles are pointed straight ahead to avoid any binding.

15. Now is an excellent time to clean and re-pack the wheel bearings; they probably need it and it"s easy to do while everything is apart. Set the wheel bearings so there is a very light amount of drag when you rotate the wheel hub, then install the lock nut and lock everything down. This is also a good time to inspect the brake pads and replace them if they"re suspect. YJ and TJ owners don"t have to do all of this; the wheel bearings and hubs are all one non-serviceable unit, which is good or bad depending on your perspective.

16. The last step is installing the locking hub. The external 5-bolt hubs used on later CJs are well-known for failure, due in part to their aluminum housings and their tendency to loosen up over time. Swapping to the stronger internal hubs used on Fords and Chevys is an excellent upgrade, but that"s a story for another time. For now, we"ll just keep a close eye on the hub bolts during each trip out to the desert.

17. Plumbing the compressor is fairly easy thanks in part to ARB"s detailed instructions. We wanted to try out ARB"s new compact compressor, which supplies the necessary air to power the lockers but has a shorter duty cycle than their larger compressor that can serve double-duty and fill up tires. We like the compressor"s small footprint, and the smaller compressor doesn"t seem to cycle as often as its bigger brother. It"s also very quiet for a compressor.

18. ARB also makes the wiring a piece of cake. The pre-assembled harness includes pre-terminated connectors and requires hooking up just three wires to the vehicle: switched 12-volt power, a ground, and dash illumination (so the switches light up when the headlights are on). Be sure the power circuit you tap can handle the 15 amps that the compressor draws. Note that ARB switches often fit in the switch blanks commonly seen on modern dashes, making for a nice, clean installation. This old CJ didn"t have any convenient switch locations, so we ordered an optional switch bracket from ARB and mounted it within easy reach of the driver. Now we have ultimate traction available at the flip of a switch, and the peace of mind knowing the axles have quality parts that can handle hardcore terrain.


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