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Next-Generation Dynatrac Dana 44

Posted in How To on October 21, 2013 Comment (0)
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Next-Generation Dynatrac Dana 44
Photographers: Pete Trasborg

Much like our hideous caveman ancestors tens of thousands of years ago, the first Dana 44s found under Jeeps in the late ’40s were simple and unrefined, coarse and archaic. Sporting 10- or 19-spline two-piece axleshafts with a keyway and a nut holding the axle flange to the axleshafts, a course 10-spline pinion, and weak small-diameter axletubes, a lot has changed over the years since the dawn of Dana 44s. While modern man carries a smart phone with more computing power than that of NASA in the ’70s, those early Dana 44s are like the club to the smart phone of the “next generation” Dana 44. Alright, maybe that’s a bit of a stretch. But hey, you have to admit that Dana 44s have evolved over the years into a much stronger axle that approaches, if not exceeds, the strength of the venerable Dana 60. All this while still maintaining a relatively girlish figure—that is, getting stronger without packing on all the excess weight. When the rear Wagoneer Dana 44 axlehousing in our ’49 CJ-3A literally broke in half at the 2013 Tierra Del Sol Desert Safari (“Unintended Consequences,” July ’13), we considered many different rear axles as a replacement. Our mind went from building a replacement Wagoneer Dana 44, to a Ford 9-inch, and we even contemplated a Dana 60. Ah, what to do?

In the Jeep’s current form, that is with a Buick V-6, granny-geared T-18, 35-inch tires, and a YJ spring conversion, we have run a couple of different Dana 44s in the rear of our Jeep. The first Dana 44 was an offset CJ-3A or early CJ-5 Dana 44. This axle was beefed up with a 30-spline Detroit Locker, a Warn full-float kit, Chevy caliper mounting brackets and calipers, and Ford 11-inch rotors. The axle still ran an old and worn 10-spline 5.38 ring-and-pinion that was living on borrowed time. At some point we had built a huge and ugly truss in an attempt to add strength to the tiny axletubes. We also disliked the thick wheel spacers necessary to get the old narrow axle to approach the width of our more-modern Dana 44 front axle. The axle worked—sort of—and we loved the disc brakes, but we had twisted splines on the short 30-spline chromoly axleshaft. That’s not good.

The second axle that served time was a Dana 44 from a ’78 Wagoneer. This axle had the same 30-spline Detroit, a new 5.38 gearset from Dana, and chromoly axleshafts and factory drum brakes that were constantly getting packed with mud. This axle seemed to be nearly perfect for the old Jeep. It was just strong enough unless we were in a bad bind. It was also wide enough to match the front axle. That was until it broke in half. So as we stood in the desert feeling hopeless our mind raced between possible replacement axles we asked ourselves if we could come up with something better. Well, for once we skipped the junkyard and went with plan B. Plan B involved calling Dynatrac to build a cutting-edge Dana 44 for our old Jeep. This axle that you see here will take our Flattie from the Stone Age to the Internet Age of Dana 44s.

What you see here built by Dynatrac is a bigger, stronger Dana 44 using JK parts like a G2 Axle and Gear 5.38 JK ring-and-pinion with a large 8.8-inch ring gear (standard Dana 44s are 8.5 inches). Both the new Dana 44 ring gear and older Dana 44 ring gears share the same inside diameter so the new Dana 44 is tooth face is nearly a 1⁄2-inch larger which allows more tooth contact between the ring-and-pinion. Also the JK gears feature a larger-diameter pinion that is the same size as a Dana 60 pinion. We also were able to upgrade to a 35-spline Dana 44 ARB Air Locker and 35-spline axleshafts from Dynatrac. Yep, that’s 1.5-inch 35-spline axles in this Dana 44, just like what’s in a 35-spline Dana 60. Our axle also has the same 31⁄8-inch, 5⁄16-inch-wall tubes that Dynatrac would build into one of its semi-float Dana 60s. So why is this not just a Dana 60 replacement? Well, it’s not quite as strong as a 60 as it has a slightly smaller ring gear (Dana 60 is 9.75 inches in diameter) and smaller carrier bearings, but it is a lot stronger than our old Dana 44. This axle also has better clearance than a Dana 60 and is slightly lighter in weight (Dynatrac estimates up to 100 lbs lighter than a semi-float Dana 60). That makes it perfect for our lightweight Buick V-6 powered flattie. Follow along as we watch Dynatrac build one beefcake of a Dana 44.

1. The first step in building our new-age Dana 44 is to machine the 31⁄8-inch 5⁄16-wall axletubes to for Dynatrac’s axle bearing ends. 1. The first step in building our new-age Dana 44 is to machine the 31⁄8-inch 5⁄16-wall axletubes to for Dynatrac’s axle bearing ends.
2. Next, the axletubes are heated with a torch so that the bearing ends will fit easily prior to being welded in place. Dynatrac’s bearing ends accept Set 20 bearings for our semi-floating offset Dana 44. That means these ends are very similar in size to ends used on Dana 60 semi-float axles as well as Ford 9-inch axles. 2. Next, the axletubes are heated with a torch so that the bearing ends will fit easily prior to being welded in place. Dynatrac’s bearing ends accept Set 20 bearings for our semi-floating offset Dana 44. That means these ends are very similar in size to ends used on Dana 60 semi-float axles as well as Ford 9-inch axles.
3. With the Dynatrac bearing ends in place, the axletube is loaded into a 1 rpm rotisserie so that a nice even bead can be laid down to hold the two parts together. The speed of the rotisserie is controlled with a foot pedal. 3. With the Dynatrac bearing ends in place, the axletube is loaded into a 1 rpm rotisserie so that a nice even bead can be laid down to hold the two parts together. The speed of the rotisserie is controlled with a foot pedal.
4. Once the bearing ends are burned on to the axletubes it’s time to press the axles into the cast centersection. To do this Dynatrac uses a 100-ton press and a proprietary jig that goes in the cast carrier to prevent damage to the centersection. This jig goes between the bearing cap ends to support the centersection. 4. Once the bearing ends are burned on to the axletubes it’s time to press the axles into the cast centersection. To do this Dynatrac uses a 100-ton press and a proprietary jig that goes in the cast carrier to prevent damage to the centersection. This jig goes between the bearing cap ends to support the centersection.
5. After the axletubes are pressed into the cast centersection, the straightness of the axlehousing is checked with this solid rod that goes through pucks resting in the bearing caps. Dynatrac has never had an issue with a new axle build, but has when retubing used axles, so they always confirm even on new axle builds. 5. After the axletubes are pressed into the cast centersection, the straightness of the axlehousing is checked with this solid rod that goes through pucks resting in the bearing caps. Dynatrac has never had an issue with a new axle build, but has when retubing used axles, so they always confirm even on new axle builds.
6. The axletubes are then rosette welded to the cast housing. Dynatrac does five-plug, or rosette welds, per axletube on a Dana 44 build like this. All Dynatrac Pro Rock axles get six-plug welds per axletube. 6. The axletubes are then rosette welded to the cast housing. Dynatrac does five-plug, or rosette welds, per axletube on a Dana 44 build like this. All Dynatrac Pro Rock axles get six-plug welds per axletube.
7. Before setting up the ring-and-pinion, Dynatrac uses silicone to seal the junction between the axletube and centersection as well as the bearing ends. This will prevent any possibility of gear oil leakage due to weld porosity. 7. Before setting up the ring-and-pinion, Dynatrac uses silicone to seal the junction between the axletube and centersection as well as the bearing ends. This will prevent any possibility of gear oil leakage due to weld porosity.
8. Our ’49 CJ-3A has run 5.38 ring-and-pinions since leaving the Willys factory all those years ago. To match this ratio, we ordered up a rear 5.38 JK ring-and-pinion from G2 Axle & Gear along with a full install kit. Dynatrac recommended a 35-spline ARB Air Locker to provide that extra traction that our Flattie needs. Luckily for us, our ’49 already has an ARB Air Locker up front to match. 8. Our ’49 CJ-3A has run 5.38 ring-and-pinions since leaving the Willys factory all those years ago. To match this ratio, we ordered up a rear 5.38 JK ring-and-pinion from G2 Axle & Gear along with a full install kit. Dynatrac recommended a 35-spline ARB Air Locker to provide that extra traction that our Flattie needs. Luckily for us, our ’49 already has an ARB Air Locker up front to match.
9. Rear JK Dana 44 ring gears have one or two bolt hole sizes machined in the back of the gear. Our G2 ring gear came with holes for both 7⁄16-20 bolts and 1⁄2-20 bolts. The ARB Air Locker that we are using for this build is for regular non-JK 35-spline Dana 44 3.73 and down (RD 147). This carrier and old-school Dana 44 ring gears use puny 3⁄8-24 bolts. Dynatrac machines out the small bolt holes (shown here) in the ARB so that they can then use the larger and stronger 1⁄2-20 bolts. The JK ring gear is very thick, so it works with the high-speed or 3.73 and down non-JK Dana 44 carrier. 9. Rear JK Dana 44 ring gears have one or two bolt hole sizes machined in the back of the gear. Our G2 ring gear came with holes for both 7⁄16-20 bolts and 1⁄2-20 bolts. The ARB Air Locker that we are using for this build is for regular non-JK 35-spline Dana 44 3.73 and down (RD 147). This carrier and old-school Dana 44 ring gears use puny 3⁄8-24 bolts. Dynatrac machines out the small bolt holes (shown here) in the ARB so that they can then use the larger and stronger 1⁄2-20 bolts. The JK ring gear is very thick, so it works with the high-speed or 3.73 and down non-JK Dana 44 carrier.
10. Just as a little added insurance against spun races, Dynatrac also adds a little green thread locking compound to the inside surface of the bearing caps. It’s this kind of attention to detail that sets Dynatrac apart from the competition. 10. Just as a little added insurance against spun races, Dynatrac also adds a little green thread locking compound to the inside surface of the bearing caps. It’s this kind of attention to detail that sets Dynatrac apart from the competition.
11. Once the desired pattern is achieved, the differential cover is bolted in place. Achieving a good pattern is easy when using good parts and setting up gears is what you do all day, every day. This image also gives you a good idea of how thick the ring gear is. This is a big ring gear with lots of tooth contact area. That means it’s strong. 11. Once the desired pattern is achieved, the differential cover is bolted in place. Achieving a good pattern is easy when using good parts and setting up gears is what you do all day, every day. This image also gives you a good idea of how thick the ring gear is. This is a big ring gear with lots of tooth contact area. That means it’s strong.
12. The final assembly of a JK Dana 44 is to set the pinion bearing preload at 20-25 in-lbs. This is done by tightening the pinion until the crush sleeve is just barely crushed. Dynatrac uses a custom-made four-arm yoke holder. Some pipe can be slipped on one of the four arms to hold the yoke while tightening the pinion nut. 12. The final assembly of a JK Dana 44 is to set the pinion bearing preload at 20-25 in-lbs. This is done by tightening the pinion until the crush sleeve is just barely crushed. Dynatrac uses a custom-made four-arm yoke holder. Some pipe can be slipped on one of the four arms to hold the yoke while tightening the pinion nut.
13. Next, Dynatrac pressed the wheel studs and Set 20 wheel bearings on and into the 35-spline axleshafts. Here you can see the difference in diameter between a 30-spline Dana 44 shaft and the massive 1.5-inch 35-spline shafts that our Dynatrac JK hybrid flattie axle will spin. 13. Next, Dynatrac pressed the wheel studs and Set 20 wheel bearings on and into the 35-spline axleshafts. Here you can see the difference in diameter between a 30-spline Dana 44 shaft and the massive 1.5-inch 35-spline shafts that our Dynatrac JK hybrid flattie axle will spin.
14. Stopping power for our lightweight Flattie will now come from a set of Ford Explorer disc brakes. Here you can see the original Explorer 5-on-41⁄2 bolt pattern next to our new machined 6-on-51⁄2 bolt pattern. The six-lug pattern is very strong and matches Toyota, many FSJs, and Chevy 1⁄2-ton 4x4s. Also gone are the days of our Willys suffering from mud packed rear drum brakes. Dynatrac offers several larger brake options, but our old school flattie still runs 15-inch wheels. 14. Stopping power for our lightweight Flattie will now come from a set of Ford Explorer disc brakes. Here you can see the original Explorer 5-on-41⁄2 bolt pattern next to our new machined 6-on-51⁄2 bolt pattern. The six-lug pattern is very strong and matches Toyota, many FSJs, and Chevy 1⁄2-ton 4x4s. Also gone are the days of our Willys suffering from mud packed rear drum brakes. Dynatrac offers several larger brake options, but our old school flattie still runs 15-inch wheels.

Will It Fit?
Dynatrac has tons of experience building axles for all kinds of Jeeps and vehicles. The axle build specification sheet includes all the important measurements. That means that when the axle arrives at your house it will be easy to install, and all specifications, such as pinion angle, leaf spring perch position, and control arm bracketry, will be spot-on. Know the legend of a Jeep in a crate? How about this picture: That is one sexy Jeep axle in a crate!

Sources

Dynatrac
Huntington Beach, CA 92647
714-596-4461
www.dynatrac.com
G2 Axle & Gear
Compton, CA 90220
310-900-2687
www.g2axle.com
ARB
866-293-9078
www.arbusa.com

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