Frame cracks around a Chevy’s steering box. Closed-knuckle front-axle assemblies on early-’70s Fords. Model 20 axles on Jeeps. Flaws. Every vehicle has at least one weakness, while others have quite a few. Some problems are easily fixed and don’t cost an arm and a leg, but unfortunately most aren’t easily remedied and require a sizable investment in order to go away.
The Model 20 was used for 10 years under the back of all CJs and is infamous for its weaknesses. Regular on-road–only use with stock-sized tires doesn’t usually aggravate these weaknesses and the diff works just fine. But once you put bigger tires on a Jeep, rocky terrain underneath it, and some extra ponies under the hood, serious breakage soon follows. A common fix and upgrade is to swap in another axlehousing, most often a Dana 44, and throw away the Model 20. But finding a Dana 44 in good shape is getting more and more difficult, and the cost of a completely rebuilt Dana can be enough to turn people away. As a result, some enthusiasts go with the enormous amount of aftermarket parts available for strengthening the Model 20. In this article, we’ll examine exactly what it takes to upgrade a typical Model 20 versus swapping in a Dana 44. We’re keeping a budget in mind and will do a cost comparison to show you how the numbers add up.
To find the pros and cons of both axles, we went to Tri-County Gear in Pomona, California. The company has been rebuilding axle assemblies for more than 10 years and can customize one to fit most applications. The staff was able to give us some straight answers, and they had several axlehousings in various stages of assembly so we could compare internal parts. of them wap out there. But there’s a catch—there are countless versions. Some are narrow, some are wide, some have tapered (two-piece) axles, and most have different widths and spring-perch locations.
The ideal Dana 44 for this swap is one from a ’72-’75 CJ, because it’s the correct width and has 30-spline one-piece axles. The spring perches, however, will have to be relocated to fit under a ’76-’86 CJ, a task that requires a skilled drivetrain shop like Tri-County. Also, some ’76-’79 CJ-7s came with a Quadra-Trac T-case and offset centersections. These will accept a Dana 44 from a ’70½-’71 CJ-5 or CJ-6 with the T18 transfer case.
Other Danas can be used, but they usually have to be narrowed or otherwise altered, which adds considerable expense. Postal Jeeps came with Dana 44s and can be picked up cheap, but there are additional difficulties with swapping one of these Danas under a CJ. The main problem is that the centersection is offset by a few inches. We’ve been told a CJ at stock height will accommodate a Postal Dana, but once the Jeep is lifted, the driveline angle gets severe and the U-joints start failing. Postal Danas are also narrower, but this can be corrected with wheel backspacing. We would stick with a Dana 44 out of a CJ.
The Bottom Line
As always, the bottom line for upgrades is the cost. Please keep in mind that the prices listed were accurate at the time this article was written and can change at any time. We didn’t include labor costs, with the exception of welding a 20, because they vary greatly from shop to shop. We went to 4 Wheel Parts Wholesalers for prices on the parts to upgrade a Model 20, and the company can ship the parts to you. The approximate price for a complete Dana 44 ready to bolt in a CJ with an open differential came from Tri-County Gear, but specific prices depend on what year Jeep you want to use and any special modifications you may need. The company can customize any axlehousing to fit your application, and it can ship complete assemblies.
The opinion you’ll get on which axle is stronger—an upgraded 20 or a stock 44—depends on who you talk to. We think a beefed Model 20 is every bit as strong as a Dana 44—perhaps even a little stronger because of the larger ring-and-pinion gears. The main difference is the price: Upgrading a Model 20 is about $350 cheaper than swapping in a Dana 44 (we didn’t include any extra swap costs, like new brake lines or parking-brake cables, because some applications don’t need these). In addition, you get a locker with the upgraded Model 20 we spec out in the chart, which would have to be added to the Dana at extra cost. Dana 44 loyalists may disagree, but we think you’d be surprised at the amount of strength provided by an upgraded Model 20, and you certainly can’t dispute the price.
Model 20
Genuine Gear axles $329.95
Detroit Locker $469.95
Welding $50
Total $849.90
Dana 44
Total approx. $1200