There's no doubt that one of the most popular and most hyped rearends is the Ford 9-inch. As bulletproof as they come, it's become the go-to rear when it comes to a high-horsepower application, be it Ford, Chevy, or Mopar. As great as the 9-inch rearend might be, they do have a few drawbacks. For one, the housing is rather large when compared to their Chevy counterparts. For those of us with lowered trucks, that can be a very important consideration. There's nothing worse than ruining that perfect bed with a hump right in the middle of it so that big, round housing can articulate properly without crashing into the bed floor. And short of that, many times there's just no simple way around it. Enter the 8-inch Ford rear.
Like its larger Ford brethren, the 8-inch Ford rear is plenty stout, only in a slightly smaller package. Introduced in 1962 as a light-duty, smaller version of the 9-inch, it was continued on through 1980 in a myriad of applications. Take a look through your local junkyard and you're likely to turn up at least a handful of them.
Now don't get me wrong, there are times and places for a big 9-inch under that hauler where an 8-inch may not fit the bill (heck, my '52 F-1 has a 9-inch). But if you're packing a moderate powerplant, say under 400 horse, and are concerned with clearance issues out back, the 8-inch makes for a great rearend.
I've had an 8-inch rear set aside for a future project in my shop for a while now and thought it was high time to get it down to the guys at Currie Enterprises to get it rebuilt and ready to rock for whatever future project I run into. It was an interesting process and by the time we were done the only items from the stock rearend left were the housing, an axle, and the pinion support. It was definitely an eye-opener as to why Currie pushes their crate rearends and why, for most applications, it's a much more logical solution.
Here's the 8-inch rear as...
Here's the 8-inch rear as it was when we pulled it out of the junkyard.
But for those who already have their hands on an existing rearend, a rebuild is a great alternative to chucking a perfectly good axle in exchange for a brand-new item. Keep in mind though that Currie produces everything from brand-new housings and axles to ring-and-pinions and various brake options. So be it a rebuild or a completely new, custom-built rearend Currie can handle it all for you.
The first step in disassembly...
The first step in disassembly is to remove the four bolts behind the axle flange that keep the axle and backing plate fixed to the housing.
The entire assembly can then...
The entire assembly can then be removed.
With the axles out of the...
With the axles out of the housing, the gearcase, ring-and-pinion, and differential can be removed as a unit.
Here's the bare housing ready...
Here's the bare housing ready to be sent off to be cleaned.
This is accomplished using...
This is accomplished using a pressure washer that utilizes steam to remove any grease and debris before it's placed in a Steelabrator machine. Similar in theory to sandblasting, Steelabrating is accomplished by blasting the object with steel shot or sand to remove any millscale from the surface.
The result is a clean, bare...
The result is a clean, bare housing. That's our 8-inch housing on the left with a 9-inch unit next to it for comparison. Note the size difference of the centersection and where it tapers to the axletubes. This is where most people run into problems fitting a 9-inch rear under their truck.
The next step is to check...
The next step is to check the housing for straightness, and fix if necessary. Currie uses a tool made especially for each application to check for straightness and a press to massage the axletubes back into spec.
Next, the bearings are pressed...
Next, the bearings are pressed off the original axles.
The bearing surfaces of each...
The bearing surfaces of each axle are then cleaned using a lathe and a Scotch-Brite pad.
A dial indicator is set up...
A dial indicator is set up at opposite ends of the axle to check for trueness.
Any deflection found is remedied...
Any deflection found is remedied using a fixture mounted in a press. One of our axles was found to be bent past Currie's specs.
Next, the bearings are pressed...
Next, the bearings are pressed off the original axles.
Here's the stock axle (left)...
Here's the stock axle (left) that checked out and the new Currie axle (right) to replace the bent one.
The 8-inch Ford rearends came...
The 8-inch Ford rearends came with two different gearcases. Notice the additional cast support ribs on the case to the left. Those ribs indicate that this is the stronger of the two and is something you should look for when searching for a used rear.
The next step is to check...
The next step is to check the housing for straightness, and fix if necessary. Currie uses a tool made especially for each application to check for straightness and a press to massage the axletubes back into spec.
Our stock differential was...
Our stock differential was a two-spider unit and the new 8-inch Ford torque sensing differential (TSD) limited-slip unit features a Ford traction lock bell that has been converted to accept four spider gears.
The new Currie 8-inch TSD...
The new Currie 8-inch TSD uses a set of clutch plates to sense the torque needs of each wheel and apply it accordingly. This is what makes a limited-slip differential work so well on the street.
Once assembled, the differential...
Once assembled, the differential is placed in a jig and hand-tested for the proper "slip." Years of experience allow the technicians to make finite adjustments simply by torquing each unit by hand and adding the necessary shims to the clutch pack.
The TSD with the ring gear...
The TSD with the ring gear installed is now ready to rock. We went with a 3.55 gear for a good overdrive-compatible rearend.
Here's another 8-inch vs....
Here's another 8-inch vs. 9-inch comparison that shows the size difference between the two ring-and-pinion units. The diameter of the ring gear is where they get their name.
The next step is to disassemble...
The next step is to disassemble the ring-and-pinion and differential from the gearcase.
Then the differential is installed...
Then the differential is installed in the gearcase along with the pinion assembly.
The Steelabrate process left...
The Steelabrate process left some debris in the housing...
...so before anything is assembled...
...so before anything is assembled to the housing, it's given a thorough lashing with a wire wheel before being carefully inspected and wiped down.
Then the axle bearing seals...
Then the axle bearing seals are driven into place.
Before the gearcase is installed,...
Before the gearcase is installed, black RTV is applied to the housing and gasket to ensure a leak-free seal.
Then the gearcase is dropped...
Then the gearcase is dropped into place and the nuts torqued to 40 ft-lb.
Our brake components were...
Our brake components were pretty spent. Thankfully, Currie offers not only a number of disc brake options, but stock drum brake replacements as well. Replacing the entire unit proved easier (and cheaper!) than rebuilding the stock items.
Here's the new brake assembly...
Here's the new brake assembly on the end of the housing.
Next, the axle is slid into...
Next, the axle is slid into the housing....
...and the four bolts that...
...and the four bolts that secure the retaining plate are tightened, effectively installing the axle and brake assembly.
New brake drums finish off...
New brake drums finish off the rearend rebuild and ensure we won't need to do a brake job for some time.
Currie has their own proprietary...
Currie has their own proprietary gear oil made specifically for their rearends. This includes a Limited Slip Friction Modifier for applications such as ours where a limited-slip is used.
The final step was to dress...
The final step was to dress the rearend in a coat of Eastwood Rust Encapsulator satin black.