Tech

Currie Enterprises 9″ Rear End Install

109Views
GM Scene Magazine®

Why Currie's 9" Ford Rear End Reigns Supreme Over Chevy Counterparts

While we appreciate many aspects of General Motors, including their commendable LS engines, it’s crucial to acknowledge one area where the blue oval enthusiasts have outshone – the design of a robust rear end. True gearheads understand the Ford 9-inch stands as a superior option, surpassing Chevy rear ends in terms of strength, durability, and overall performance capabilities. Despite the widespread use of these rear ends in various vehicles, finding one in a junkyard proves to be a challenging task. Thankfully, Currie Enterprises comes to our aid by offering an excellent new version of these highly regarded components.

While it’s arguable that a relatively solid 12-bolt can be constructed, the undeniable reality is that it falls short when compared to the 9-inch. A major concern lies in the fact that a single clip holds each axle in place on a 12-bolt, posing a potential point of failure. Servicing the internal components is also a more complex task, necessitating a complete rebuild for the replacement of nearly any internal part.

The aftermarket support for the Currie 9-inch serves as a testament to its superiority. In contrast, Chevy counterparts fade in comparison when it comes to the myriad of options available for customization. Whether it’s gear ratios or limited-slip differentials, the Currie 9-inch offers a plethora of choices, empowering you to fine-tune your rear end with precision. This level of customization is a game-changer, placing you firmly in control of optimizing performance.

Maintaining the Currie 9-inch is a breeze, setting it apart from Chevy rear ends. Its user-friendly design, featuring a removable third member, simplifies gear changes and maintenance procedures. No longer do you have to grapple with the complexities of shimming or setting gears in-house; the 9-inch rear end allows you to remove it as one piece from the unit, reducing downtime and maximizing the enjoyment of your classic ride.

Let’s delve deeper into the realm of customization – an area where the Currie 9-inch reigns supreme. While Chevy rear ends might offer some options, they pale in comparison to the versatility provided by the Currie 9-inch. This rear end isn’t merely an upgrade; it’s a canvas for personalization. Choose gear ratios that align with your driving style, opt for a limited-slip differential that enhances traction – the possibilities are boundless, enabling you to sculpt the performance characteristics of your vehicle with precision.

First off, Currie 9-inch rear ends come in three different options, the Hot Rod version (left) has tubes buttwelded to the narrowed center making more room for suspension bracketry. Next is the Centurion 9-inch (middle) was modeled after an original from an F-100 and has more strength as the tubes have 4-inches of overlap from the center housing. Getting the best of both worlds is the F9 (right) as its bent construction adds extra structural integrity with more tube engagement in a narrow package. All are made of 3/16ths steel, which is thicker and stronger than the material used on factory Ford 9-inch rear ends.

Currie uses 3-inch diameter tubes with .188 wall thickness for strength. Here you can see the various lengths of tubes ready for specific rear end widths.

Then the housing gets studs pressed in from the inside in order for the third member to get secured on later.

After 9-inch centers are fabricated, they first get a drain plug to make gear oil changes easy. The holes are first drilled and then followed by a ½-inch pipe thread tapping bit.

Tubes are then mocked up with the housing and ends with an alignment bar in place to help make it all straight. The pieces are then measured to fit each specific application before getting locked in together.

As another additional option Currie offers a full-floating ends with a heavy-duty uni-bearing for extra durability.

Once the rear end is in place, the center, tubes and ends are all fully welded up.

Currie checks the straightness of each rear end and if readjusting is needed, they are tweaked with the use of a special tool on a press. Straightness is then checked with an alignment bar that goes into the housings.

These 9-inch rear ends are available with a variety of different mounting brackets including ones for original leaf springs or multi-link suspension systems. Currie also has offerings for popular aftermarket options like Detroit Speed and Ridetech suspension systems.

Rear ends are made in batches of 7-10 to keep most popular applications in stock so that they are pretty much ready to go when ordered. All their 9-inch rear ends can be ordered powdercoated and fully assembled or as individual pieces for the DIY builder to add their own finishing touches before final assembly.

Housing are batch made off-site, but when ready are assembled. Since every piece is made with precision, there is very little guesswork when it comes to putting them together. Given each specific gear option, the crew knows roughly how many shims to lay between the housing and pinion/yoke unit.

Since most builders are getting a Currie 9-inch as a performance option, the go-to differential is a Currie Twin Trac limited slip. Though, an open diff can be custom ordered if desired. The team assembles them with a number of gear options but most popular is 3.50, 3.70 and 4.11.

Once the unit is together, the diff assembly is secured into place with a set of bearings, brackets and hardware. One thing to note here is the size of all the components here, which are designed for maximum strength.

The team then measures backlash to make sure the gears are within a specific tolerance. Gear marking compound is spread on the gears in portions and diffs are then put in motion with a drill. This will show where the pinion gear and ring gear make contact. This is very important in making sure the gears synced correctly and if not, shims can be removed or added to adjust them accordingly. As you can see good pattern on the center of the teeth meaning that there is good contact between gears. Another thing to note about these rear ends is that the pinion is moved off center and the gear teeth are longer for more engagement.

Here is what a finished third member will look like when completed. Currie keeps many popular third members in stock and ready to go. If you order a rear end unassembled, it will come in one of these specially designed boxes that were made to prevent damage during shipment.

Whether you install the third member or Currie does it, the connection to the housing must be sealed to prevent gear oil leaks. First, a bead of high-temp black RTV on the housing and around the inside of the studs. Then the gasket is laid down and another bead of sealer is laid over.

When bolting down the third member, the two bottom nuts need to be loosely installed before the two pieces of the rear end are butted together. Do note that these nuts have to be attached in this order as the third member housing will get in the way of attaching and removing them when the other nuts are installed and tightened down.

Currie uses axles made from forged 1541 induction heat-treated material and they come with bearings installed. Most common applications have 31-splines for strength and durability, but other options are available.

The axles are dual drilled for 5 on 4.5 and 4.75 for popular GM car applications and cam come with or without studs pressed in.

The axles simply slide in from the ends, which makes installation easier. They are held down by a bracket on the ends and hardware can be attached by use of a socket running through a hole on the end of the axles. As you can see here, Currie attached factory style drum brakes and there are a number of options including no brakes if you wish to handle this portion on your own.

Here is an assembled 9-inch with an aluminum third member ready to be shipped out to a customer. After installation, it is recommended to use conventional 85W-140 non-synthetic GL-6 rated gear oil and change after the break-in period. Currie also recommends starting out by driving for about 30-minutes to an hour and letting it cool off for 15-minutes. Varying RPMs in the process for the first 200-miles will introduce heat to in intervals to ring gear, making for an optimum break-in period. Afterwards, your 9-inch will be able handle any street driving your car can dish out for years to come!

Currie Enterprises
328 N. Smith Ave
Corona, CA 92878
(714) 528-6957
currieenterprises.com

GM Scene Magazine®