High-Performance Differentials, Axles, and Drivelines. Joseph Palazzolo
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The 489, the last variant, was phased in to replace the 742. It has a tapered pinion stem diameter of 1⅞ inches. The casting numbers from 1969 to 1974 were 2881488 and 2881489. The 489 has a large number 9 cast on the left side. There were some 1¾-inch pinions installed in the 489 casting during this time period, so you ought to inspect the axle carefully to confirm which one you’re looking at.
So which one do you want? Supposedly, the larger the pinion stem, the stronger the axle. The axle center sections are interchangeable, so if you have the weaker 741, you can easily upgrade to a 742 or 489 without too much trouble. As with any upgrade, take the time to do your homework.
Also, take note that most Chrysler axles have left-hand or reverse-threaded ring gear bolts. Left-hand threaded bolts self tighten when the joint is loaded, which counteracts any tendency to loosen. These are ideal when the bolt is on the center of rotation—like the bolt that holds your lawn mower blade to the crankshaft. However, ring gears and wheel studs are not lined up on the center of rotation, and therefore do not benefit from this opposite-hand thread. For some reason, Chrysler used this on their ring gears and driver’s-side lug nuts in the 1960s and 1970s. General Motors used the same design philosophy for some of their axles.
This is a typical gasket for the Dana 60 rear cover. It has 10 holes and is just over 12 inches in diameter. (Randall Shafer/Joe Palazzolo)
A typical Dana 60 stamped rear cover is easy to spot because it has the Dana logo and telltale fill plug. The ring, pinion, and splines are incredibly strong. Plymouth and Dodge muscle cars used this stout rear end to transfer enormous torque loads to the wheels.
The Strange Engineering version of the Dana 60 features adjuster nuts that are used to set the hypoid bearings preload and gear backlash, which is a great addition to an already great axle. The dial indicator is in position to check
Dana 60 Axle
Just like many of the manufacturers in this text, Dana has many different-size axles and combinations available. I am going to concentrate on the Dana 60 (D60). It has a large 9¾-inch ring gear and was used in many different Mopar truck applications, passenger cars with 440, 4-speed combinations, and the legendary 426 Hemi cars. This axle is far superior in strength and efficiency to the Ford 9-inch. For some reason, Chrysler was the only OEM to use the indestructible D60 in their muscle cars.
Typically, you can build a custom D60 for one-third less than the cost of a Ford 9-inch. Unfortunately, you cannot get a D60 for certain applications—one being the Ford Fox platform. However, if the ring gear in your muscle car is less than 9 inches and it cannot handle the torque input, you should opt for the Dana 60. Many sub-9-inch axles cannot hold up when horsepower rises to 800 or 1,000 or more.
The D60 hypoid offset is half that of the Ford 9-inch. Therefore, less torque is lost and less heat is generated in the D60. There are many aftermarket companies that make their own version of the D60, such as Strange and Teraflex. Most of the D60s use a solid spacer, while some use a collapsible spacer, to set the pinion bearing preload. The spacer needs to be adjusted to obtain the correct preload, and then the nut is tightened to the correct torque value.
Ford Axles
Ford has produced its own corporate axles just like GM and Chrysler. Some of these axles are similar to the other OEMs, while others are unique, such as the Ford 9-inch. We are going to review the more common available axles.
Not all banjo-style Ford axles are in the best condition from the factory. This housing has been media blasted, and you can see a weld repair was performed to correct a poor factory weld.
Ford 8-inch: It may seem strange to compare the 8-inch to the 9-inch because the 8-inch axle is weaker than the 9-inch. However, an important distinction needs to be made. Many people are not aware that Ford made a smaller banjo axle and confuse the 8-inch with a 9-inch. There’s an easy way to tell them apart. An 8-inch has case nuts that can be accessed with a socket, while the 9-inch has two nuts on the bottom around 6 and 7 o’clock that cannot be accessed with a socket and require a wrench. Both axles share a common design, but the little 8-inch just cannot handle the abuse like its bigger brother can. The 8-inch also was only available with 28-tooth axle shafts.
Here is a typical aftermarket triangulation support welded on the tube to reinforce the tube. Notice that this axle has the tubes welded solidly to the cast center section. This aftermarket process is not found on production housings. (Randall Shafer)
Also, don’t confuse the later pictures in this chapter that show independent 8-inch carriers with the 8-inch banjo-style beam axle housing. Both 8-inch and 9-inch axle housings are made from a series of stampings that are fixtured and welded together. This complex fixturing and welding process, coupled with fuel economy concerns, most likely led to the production demise of these Ford axles. In high-volume production, the two biggest quality problems were leaks from poor welds and poor alignment of the housings. So don’t be surprised that most of these axles leak from the welds. Careful aftermarket shops, with their stringent attention to repairing these housings, are able to correct many of these issues.
The usual 10-bolt gasket surface of the Ford 8.8-inch axle does not have the lube slots at the 3 and 9 o’clock positions as on the GM 12-bolt. The Ford axle relies on oil being indirectly channeled behind the caps from splash and churning of the gears. The oval-shaped cover is about 10 × 10 inches. (Randall Shafer/Joe Palazzolo)
An aftermarket chrome Ford 8.8-inch stamped rear cover does not have the lube shelf as on the GM 12-bolt axle. Therefore, it
Ford 8.8-inch: The Ford 8.8 inch is very similar to the GM 8⅞-inch, 12-bolt axle. Some folks may tell you that the Blue Oval engineers copied the 12-bolt design when they came up with the 8.8-inch axle. While that is a matter of opinion, one should recognize that there are many similarities. It is interesting that the Ford axle uses the exact same bearings as the GM 12-bolt. The Ford version uses larger axle shafts and a different lube strategy, but otherwise they are very similar axles.
A common Fox chassis Mustang is usually equipped with an 8.8-inch rear axle. This one happens to have a stamped-aluminum rear cover, which provides improved that are lighter cooling. Some of the truck versions had composite covers than aluminum. (Randall Shafer)
This rare Ford 8.8-inch independent carrier axle with a cast-iron housing was fitted to late-model Mustangs and Ford Explorers. Notice the 8.8 cast into the housing above the pinion.
This Ford Explorer 8.8-inch independent axle has a cast-aluminum housing. The sensor in