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Factory Five Roadster Build Part 6 - Rearend InstallOur Project Gets Rearended (But That's a Good Thing!) From the November, 2006 issue of Modified Mustangs & Fords By Mark Houlahan Photography by Courtesy of Drivetrain Specialists, Mark Houlahan
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Our 8.8-inch axle assembly... Our 8.8-inch axle assembly arrived safely strapped to a shipping pallet via FedEx ground freight. The assembly, as built here, minus brakes, set us back $2,100. We had to pick up gear lube (DTS suggested 90W-140 for break-in) and a Ford replacement axle vent assembly (PN E4LY-4022-A, $13). We're itching for the day we can bolt on the wheels and tires to our Factory Five Roadster and roll it out of the garage. It'll be the first time since early February when we placed it on four jackstands for the beginning of the project. While we're only about halfway through the project, making it a "roller" will be a big turning point for us. There's still the drivetrain installation, lots of wiring, body fitment, painting, and more before the project will near completion, and then we still have to title, register, and insure the car. With so much to do, we'll take the small victories anytime we can. Of course, we can't bolt up our wheels without suspension and hubs/drive axles. In Part 3 in the August issue, we installed the majority of our Roadster's suspension parts. This month, we take delivery of a custom-built axlehousing and bolt the Factory Five mounting brackets to it for installation into the Roadster's frame. Next month, we'll install the rearend and brakes. Then we'll be able to get our wheels in place. Once they're on, we can set ride height via the adjustable coilover shocks and torque all of the suspension hardware one final time. It doesn't really matter what... It doesn't really matter what 8.8-inch housing DTS starts with since it cuts the axle tubes to the proper length for the application. We had the company install 9-inch Torino bearing ends to the axle tubes. This is a much safer way of securing the axleshafts to the housing than the stock C-clips the 8.8 uses. If you want the whole 9-inch package, DTS offers 9-inch housings for late-model Mustangs that will work in the Factory Five application as well, including the FR/9 housing with improved geometry for better traction. As many of you know, the Factory Five Roadster is based around using donor or new parts designed for the hugely popular '86-'04 V-8 Mustang, including the drivetrain. For the rear-axle portion of our build, we had several options, including installing a 9-inch Ford housing designed for said Mustang model years, or a production Mustang housing, again from said model years, which is Ford's corporate 8.8-inch housing with integral carrier gear design. The 8.8-inch housing is immensely popular for its strength and light reciprocating weight, and can be found in everything from Mustangs to F-series trucks, Explorers, Crown Vics, and Lincoln Town Cars. Even classic Mustang owners are swapping to the 8.8s, but that's another tech story. The '86-'93 Fox Mustang housing is what the original Factory Five dimensions are based upon and offers the widest rear-wheel choices because it is the narrowest Mustang rear at 59-1/4 inches. The '94-and-up rearends grew wider as the body style changed and disc brakes were added. If you are on a budget, the stock 8.8-inch housing will work fine for a donor build, but with the 500 hp we'll have on tap, we decided to build something a bit stronger while still allowing bolt-in functionality of the Factory Five suspension parts. We contacted Drivetrain Specialists (DTS) in Michigan for some ideas. We knew we wanted the narrowest rear possible for some serious rear rubber, so DTS obliged by building us a "Fox width" axle assembly and stuffing it with all sorts of goodies from Eaton, Strange, Ford Racing, and more. After discussing the details with Mike Rosales at DTS, he had his guys Adam, Patrick, and Josh break out the welder and pull the parts from stock to build us one tough rear axle. DTS not only offers parts for most any rear for repairs and upgrades (such as gears, bearings, and seals) but it can custom build just about any rearend you can think up-such as our 8.8-inch unit for our Roadster-including custom fab work, powdercoated housings, brake kits, and so on.  The factory 8.8-inch housing...  The factory 8.8-inch housing uses a cast centersection with steel axle tubes. The tubes are pressed into the cast center and then a weld "button" is used to secure them. To prevent axle tube distortion under power, it is common practice to weld the tube to the centersection. Here the axle tube and centersection have been ground clean in preparation for welding.  Pat from DTS carefully welds...  Pat from DTS carefully welds the joint in a 360-degree fashion, using a custom work stand that allows him to rotate the housing during the welding process. The axle tubes are checked and straightened during the process, and the billet 9-inch ends are welded after the tubes.  Here's the completed weld...  Here's the completed weld that prevents the axle tube from moving in any way. We've seen a few 8.8s leak oil from this joint, so the weld will prevent this as well.  The 8.8-inch housing is an...  The 8.8-inch housing is an integral carrier design, which means the differential and gears are installed into the housing and not a removable carrier or "pumpkin" like the older 8-inch or 9-inch units. We opted for an Eaton Posi unit for this axle build. The Eaton Posi (PN ED 19588-1, $505.60) is a tough unit, with 400 pounds of preload and 31-spline side gears (more splines equal more surface area for strength).  As you can see by the exploded-view...  As you can see by the exploded-view diagram, the Eaton Posi is a clutch-type differential. The clutches use super-tough carbon fiber for the friction plates. Forged gears add even more strength to the unit, and the whole thing is rebuildable, just like a stock Ford Traction-Lok.  When swapping rearend gears,...  When swapping rearend gears, it's smart to install all new bearings and seals. This was pretty much mandatory since DTS started with a bare housing from its inventory (you can send the company your own housing as well). This complete bearing, seal, and shim kit (PN IK 83-1013 $128) has Timken bearings for the differential and pinion gear, ring-gear bolts, cover gasket, pinion nut, gear-marking compound, and more.  If you ask your late-model...  If you ask your late-model Mustang friends, they'll tell you that 3.55s are the minimum gear to upgrade to (remember, these cars have Overdrive), and many go to 3.73s and even 4.10s. But these cars also have 3,500 pounds to push down the street and only 300 to maybe 400 lb-ft of torque with which to do it. When completed, our Factory Five Roadster will weigh around 2,200-2,500 pounds and will have over 500 lb-ft of torque. With these numbers in mind, DTS recommended a 3.27 ratio to match our power and our Tremec TKO-600 transmission gears. DTS carries several brands of gears, but Ford Racing Performance Parts 3.27s (PN FM M-4209-F327, $248) got the nod for this build.  The FRPP ring gear is placed...  The FRPP ring gear is placed on a set of press plates, and the Eaton differential is carefully seated with the press. Once seated, the new ring-gear bolts are installed and torqued to Ford's specs of 70-84 ft-lb.  The same press is used to...  The same press is used to push the new carrier bearings into place with the aid of a special-sized spacer to press on the inner race of the bearing only. This prevents warping the cage or damaging the bearing rollers.  The same steps are performed...  The same steps are performed on the pinion gear and its new bearing.  If you've ever watched someone...  If you've ever watched someone work on a Ford differential, you've probably seen an item called a crush sleeve being installed. A crush sleeve is installed on the rear of the pinion gear to set pinion depth and helps set up pinion bearing preload when the pinion nut is torqued to the proper specs. The problem is, on high-powered cars with locking or high-bias differentials, they place more load on the pinion crush sleeve than normal and will actually compress it further, changing pinion depth. A solid crush sleeve (PN IK 4105, $16.32) prevents this distortion, and the pinion depth and preload is set by shims.  After installing the pinion...  After installing the pinion gear and setting pinion depth, the differential and its mounted ring gear and bearings are placed into the housing with a preliminary shim pack. Gear-marking compound is used on the ring-gear teeth, and the ring gear is inspected for the proper pattern and backlash via a dial indicator.  If the ring-gear backlash...  If the ring-gear backlash is out of spec, the carrier shims are adjusted from side to side, and the pattern can be further adjusted by changing the pinion depth.  Once the crew at DTS gets...  Once the crew at DTS gets the backlash and pinion depth finalized, the carrier bearing caps are torqued to their factory specs of 76-89 ft-lb. DTS can optionally install carrier bearing studs and billet steel caps for even more strength.  Here, DTS uses Strange Engineering...  Here, DTS uses Strange Engineering 31-spline S/S series alloy axles. New axle bearings are pressed on before the axles are installed. The 9-inch bearing ends utilized on our housing require 9-inch-style bearings, of course. The 9-inch-style bearing is superior to the stock 8.8-inch-style bearing for two reasons: One, the bearing is simply larger and can take more load, and two, the bearing has a true inner race whereas the 8.8-inch axle bearing uses the axle shaft itself as an inner race. This means if the bearing goes bad on a stock 8.8, it usually takes the axle with it. Ouch.  To cap everything off, DTS...  To cap everything off, DTS installed one of its aluminum support covers (PN TA 1806, $160) in place of the stock stamped-steel unit. The aluminum cover uses load bolts to spread the carrier bearing load to the substantial differential cover and out to the housing. This prevents gear and bearing wear by holding everything in place. The cover also allows easy oil fill and drain servicing. The front of the housing received a new Mustang-style companion flange (PN FM E9TZ-4851-A, $44) to receive our upcoming driveshaft.  The Factory Five rear lower...  The Factory Five rear lower control arm brackets attach over the factory brackets welded on the rear itself. The attachment is via 1/2-inch bolts, which requires the factory mounting bolt holes to be drilled out (they're metric on the late-model Mustang). You can find 1/2-inch drill bits with reduced shank diameters that will fit in a 3/8-inch drill.  The Factory Five brackets...  The Factory Five brackets are a snug fit over the factory brackets on the rearend and will require some force to seat. A rubber mallet and a lady-foot prybar through the bolt holes did the trick for us. We also drilled the shock mounting bolt hole with the 1/2-inch drill bit, and placed a 1/2-inch bolt through the shock mounting bolt hole to help keep the bracket in alignment while tightening the other bolts.  For our Factory Five 3-Link...  For our Factory Five 3-Link suspension, we'll also have to mount the upper link bracket to the housing. Commonly called a "banana" bracket due to its shape, it is clamped around the passenger axle tube.  The bracket is fitted to the...  The bracket is fitted to the axle tube and butted up against the iron centersection of the housing. Start all four bolts loosely and tighten them a little at a time to draw the bracket together around the axle tube.  The bracket is fitted to the...  The bracket is fitted to the axle tube and butted up against the iron centersection of the housing. Start all four bolts loosely and tighten them a little at a time to draw the bracket together around the axle tube.  When the axle bracket was...  When the axle bracket was drawn together by the four bolts, we noticed the axle vent hole had a small section of the bracket covering it. We determined the cause was that the weld bead at the end of the axle tube prevented us from butting the bracket up against the centersection. We plugged the vent hole and carefully trimmed away the bit of bracket blocking the vent hole.  Another casualty of having...  Another casualty of having our bracket bumped over a bit was the alignment between the axle bracket's support leg and the differential center section location it bolts to. The gray iron center drills easily, so we ran a drill bit through the bracket's support leg end and made a new hole for the mounting bolt.  These two minor modifications...  These two minor modifications were due solely to welding the axle tube, so most of you won't have to do this. Next month, we'll install the brakes, and hopefully our Roadster will roll out of the garage for the first time. Stay tuned.
 | Project Snake Charmer is finished and on the road Check out the diary for more! |  | We'd like to introduce you to Mustang & Fords' new project, Project Snake Charmer |  | We Go Back to School-and Like It! The Factory Five Racing Cobra Roadster Kit Car Buildup Series Continues At The Build School. |  | Our Factory Five Roadster Suspension Finds Its Way to Our Frame |  | Our Factory Five Roadster gets its motivation from a Smeding Performance 427 |  | We install and prepare the aluminum panels for Project Snake Charmer |  | Our Factory Five Roadster gets a Drivetrain Specialtists rear end for Project Snake Charmer |  | Our project becomes a roller with brakes, wheels, and tires |  | Project Snake Charmer receives an EFI based fuel system to feed the snake |  | Our Factory Five Racing Roadster recieves a Smeding Performance 427 Windsor and a Tremec Transmission |  | Our Factory Five Roadster gets a new dash, pedals, and cooling system |  | Installing the Factory Five Racing wiring harness on our Project Snake Charmer Cobra Roadster Replica |  | We finish up the wiring and then turn towards starting the body on our Factory Five Roadster Project Car |  | Installing hydroboost brakes on our Project Snake Charmer Factory Five Roadster before painting |  | Project Snake Charmer Factory Five Roadster heads off for paint |  | Our Factory Five Roadster Begins the Paint Process |  | Our Cobra Replica's Almost Ready For Paint |
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