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Custom Built Axle and Wheeltubs - Pro Street Posture
Fittin' The Fatties
From the September, 2004 issue of Sport Truck
By Gary Blount
Photography by Gary Blount
Tuckin' rim is a shared denominator for both 'bagged and hot-rod trucks. The trend, however, stemmed from a class of custom builds labeled Pro Street. This label came from the influence of the drag race class known as Pro Modified on street-driven vehicles. The look of the lowered vehicle sitting over massive meats renders a very dramatically impressive stance. This look was incorporated into street-rods everywhere by the early '80s as the look of choice. The trend carried over into the truck market, and the rest, as they say, is history. The reason for the change in stance initially came from functionality. Pro Mod drag racers set up their suspension for maximum traction and launch. Four-link bars attached to brackets on the differential transfer the twist pressure and forward motion generated by gobs of power through the leverage brackets welded to the differential. The links are positioned on the frame to render a perfect launch. The two upper links pull on the top of the frame, which raises the nose of the vehicle and transfers weight to the rear tires for maximum traction. The lower links are placed farther forward on the frame, which allows the differential to push the vehicle forward in a straight line. The new suspension allowed the vehicle to be lowered, which optimized center gravity for weight transfer, wind resistance, and stability. Today, there are many different types of custom setups to choose from when getting the altitude adjusted for the desired attitude: four-link, three-link, triangulated-link, airbag, inverted leaves, and so on. Regardless if you're running a set of Hoosier Pro-Street Radials or some Pirelli Scorpions wrapped in a set 22s, getting the rubber to tuck under the stock body can be tricky. Cutting the bed of the truck is common, but it's not the only trick needed to get big meats to squeeze between the framerail and outer body panel. Frequently, rim offset and tire combination are compromised to make the rolling stock fit. This is a makeshift way of getting what you want, and it doesn't always end in success. If you aren't concerned about the punishing forces of power, you could have your stock differential housing tubes cut down and custom axles cut to make room for your rolling stock. Or you could call Dynatrac to build you an axle that would be a bolt-in replacement with disk brakes for about $3,000. Not only will you get an awesome axle that is virtually indestructible, but you will also be able to fit the rim and tire of your choice without worrying about clearance issues. Here's the show-and-tell on a custom-built axle and wheeltubs.  1. Even though the stock frame...  1. Even though the stock frame width allows for much larger meats, the shackles and springs prevent using the space. You can also see that the rim of choice had the maximum offset for clearance. For some, the front-wheel-drive rim look is desirable, but some builders would rather tuck rims with some rim lip. Even if you like the look of a no-lip rim, pulling the rim and tire combination under the stock sheetmetal is still essential when laying frame.  2. Ford 9-inch differentials...  2. Ford 9-inch differentials became popular for the ease of shortening them with little modification. But Dynatrac's Dana 60 is a far superior piece than a junkyard axle that needs modification. Dynatrac's axle tubes (left) are drawn-over mandrel steel, and are stronger than the sleeved 9-inch tube (right). The 9-inch axle tube is sleeved to step down from the axle flange diameter to the differential housing hole. This means that one tube is fixed to the flange and one tube is fixed to the housing. They are slipped together and plug-welded. This leaves all the power placed on the differential as shear pressure on the plug welds. The plug welds fail under the pressure, and frequently break or leak. Dynatrac axle tubes are 3-1/8-inch single-piece tubing, which eliminates the issues with two-piece axle tubes that are 5/16-inch thick.  3. Another major advantage...  3. Another major advantage of Dynatrac's differential is its billet steel axle flange. As seen here, the Dynatrac axle flange is 0.830-inch-thick steel and is beefier than the Ford 9-inch rear diff flanges. Filled with induction-hardened alloy steel axles, Dynatrac axles are some of the strongest in the industry.  4. Dynatrac's Dana 60 housings...  4. Dynatrac's Dana 60 housings are not rebuilt junkyard units; their housings are cast in nodular iron. Many differentials are still made of cast iron, which doesn't have the equal strength or ductility (elasticity or memory) that Dynatrac's proprietary-nodular-iron casting provides. Plus you won't need to worry about a bent housing or worn-out and misaligned bearing areas.  5. Axle tubes are cut to fit...  5. Axle tubes are cut to fit your application, and a large taper is cut on the flange end of the tube for excellent weld penetration.  6. Billet steel flanges are...  6. Billet steel flanges are cut 0.001 to 0.002 inches over the inside diameter (id) of the tube for a good, tight fitment. A torch is used to heat up the axle tube, which expands the id to allow the flange to slide easily in place.  7. Wire-feed welders can leave...  7. Wire-feed welders can leave molten fragments of metal spattered all over the new components. A spray-on antisplatter agent by the name of Jokisch is sprayed on the exposed areas to ensure your tube and flange will be free from the molten mess.  8. After allowing the tube...  8. After allowing the tube and flange to cool, the component is placed on a rotating welding station where the tube and flange are coupled together with a smooth weld.  9. The finished product speaks...  9. The finished product speaks for itself. The new flange and tube are ready for the next step in the assembly phase.  10. An adjustable fixture...  10. An adjustable fixture is set inside the differential housing to hold it ridged and prevent distorting the housing while the axle tubes are pressed into it.  11. The hosing and axlehousings...  11. The hosing and axlehousings are placed in the press and prepped for axle tube integration. The housing sits flat on the press table and the axle tubes are set at the corrected angle to accommodate your pinion angle and brake placement.  12. With the pinion angle...  12. With the pinion angle set, the press pushes the axle tubes and differential housing together.  13. It takes about 30,000...  13. It takes about 30,000 psi to press the housing and tubes together.  14a. After pressing the tubes...  14a. After pressing the tubes into the housing, the diff is checked to make sure the three pieces are true. Alignment is crucial to the performance and wear of an axle; this is where buying a Dynatrac purpose-built axle comes into play. You will never find a junkyard axle that is as true as a new differential. The quality of a Dynatrac axle cannot be met by a high-production, mass-produced axle.  14b.  15. Making sure the axles...  15. Making sure the axles don't twist in the housing or move from true, the tubes are plug-welded to the housing. The reason for not welding the tube to the housing around the press area is that it would fatigue the nodular iron and pull the tube out of alignment. Nodular iron is a control-cooled cast to increase strength. Welding to it decreases the tinsel and ductile integrity, so plug-welding still fixes the tube to the housing, but doesn't compromise the mounting area on the casting.  16. As you can see, we pulled...  16. As you can see, we pulled the truck bed off and welded in the notch necessary to clear the suspension drop.  17. We gave Dynatrac the measurements...  17. We gave Dynatrac the measurements needed to figure out the pinion angle, but we were unsure of the bracketry. We opted to have the company ship us the axlehousing empty first so we could figure out our bracket setup. We had Sleeper Suspension in Laverne, California, set up the differential.  18. After mocking up the differential...  18. After mocking up the differential to the rear frame, measurements were taken and marked on the diff for placement.  19. Sport Truck's project...  19. Sport Truck's project truck Hemi Ram was equipped with a 725hp/750-lb-ft engine, so a four-link system was the only way to go for our Pro Street beast. Jim Sleeper fabbed the four-link and bracketry to the differential.  20. After figuring out the...  20. After figuring out the bracket locations, Sleeper tack-welded them in position on the axlehousing. And back the differential went for final assembly.  21. Dynatrac doesn't make...  21. Dynatrac doesn't make gears or lockers, but it certainly sets them up in its plug-and-play axle assemblies. Reider Racing Enterprises Inc. is a one-stop shop for gears and locking diffs. We employed its services for the goods and had them shipped to Dynatrac.  22a. After the locker and...  22a. After the locker and ring were bolted together, they were inserted in the differential housing and aligned with the pinion gear. With the pinion set to the right depth, the ring was shimmed to match the proper gear contact. Dynatrac set up the differential right at 0.008 of backlash.  22b.  23. Both ends of the axle...  23. Both ends of the axle shafts are sealed to prevent gear oil from seeping out of any minute passage.  24. With the axle seals in...  24. With the axle seals in place, the axles are slid into the axle tubes and the carrier assembly.  25. Four bolts hold the axle...  25. Four bolts hold the axle in the differential, three of which also hold Dynatrac's optional disk brake kit.  26. These billet steel brackets...  26. These billet steel brackets are electroplated to prevent corrosion, and provide a mounting location for the disk brake setup.  27. With the brackets in place,...  27. With the brackets in place, the floating disk brakes bolt to the bracket. These brakes are a GM-style caliper, which means replacement parts are easy to find and inexpensive to replace.  28. Dynatrac has a regimented...  28. Dynatrac has a regimented quality-control system in place to prevent flaws in manufacturing. A checklist is gone over at every stage in the build and follows the differential through the process until its completion.  29. Dynatrac also marks its...  29. Dynatrac also marks its differentials with a build code, so the job's workflow can be pulled out of the archive at any time for customer service; Not to mention that the company's differential covers are pretty cool and functional for servicing the diff. Fitting the Ram with the Pro Street meats meant the total length on our rear axle from brake to brake is 58.38 inches.  30. With all the brackets...  30. With all the brackets in place, bolting in the differential was a cake walk. The 700-plus power in our Ram needed to have dialable dampers, so Eibach springs and Koni coilovers were the answer. Dual-rate springs are placed on the damper for street driving, and the single spring rate seen here is for quarter-mile quickness. Bedside Manners
Clothing the Pro Street Posture
Tubbing the bed and relocating the fuel tank were musts for our new stance. Competition Engineering has tubs you assemble and cut to fit your application. Cruising around in a 700-plus horsepower engine means frequent fuel stops will be taking place. Summit Racing can cut down on the gas stops with its own line of large-gallon fuel cells that are plug-and-play. This one holds 22 gallons of fuel and fits well below the bed line on most trucks.  1. Hoosiers Pro Street radials...  1. Hoosiers Pro Street radials come in a variety of sizes. Our 31x18.5R17 fits over a 17-inch rim and is 31 inches tall and 15 inches wide. Billet Specialties Vintec Dish rims are a modern-made old-school-styled rim. This rim and tire combination really helps to set off our Pro Street posture.  2. To fit the tubs to our...  2. To fit the tubs to our bed, we took the radius section of the new tubs and marked a centerline through it for centering the tubs to the opening.  3. We cut out the stock wheelwell,...  3. We cut out the stock wheelwell, removing just a minimal amount of material. We also removed the bed structure all the way to the frame mounting area. We know we will need to remove more, but we need to see how the tubs will fit. Cutting out too much just adds more work.  4. We measured how the bed...  4. We measured how the bed sits on the frame and the center of the rear axle location to the bed. We then transposed this number to the bottom of the bed for the center axle reference point.  5. With the wheelwell removed...  5. With the wheelwell removed and the axle center point marked on both the bed and tub, we aligned the wheeltub to the bed. Then we slowly removed material from the bottom of the bed until we got the tub to slide into the opening at the maximum depth.  6. With the tub in place,...  6. With the tub in place, we marked a reference line on it in relation to the bottom of the bed.  7. A large straight-edge was...  7. A large straight-edge was place on the tub to prep it for cutting. We used a plasma cutter to remove the extra material, leaving the radius section of the tub with the proper height.  8. The wheeltubs have what's...  8. The wheeltubs have what's called a Pittsburgh locking seam on them. You lay the mail edge into the female seam and knock the corrugated edge over to lock the two pieces together. We didn't cut the ends off the tubs to allow for any additional work we might have to form to.  9. With the two pieces coupled...  9. With the two pieces coupled together, the tub starts taking shape and light at the end of the tunnel can be seen.  10. We wanted the tub to extend...  10. We wanted the tub to extend all the way to the framerail, so we measured that distance, added an inch for tabs needed to attach the tub to the bed, and cut the excess material off.  11. We wanted the tub to extend...  11. We wanted the tub to extend all the way to the framerail, so we measured that distance, added an inch for tabs needed to attach the tub to the bed, and cut the excess material off.  12. We wanted the tub to sit...  12. We wanted the tub to sit on the bed, so we measured off the bed with an additional 2-1/2 inches for an attachment area. With all the marks in place, we drilled holes for the cutting tip for a clean seam.  13. The mark on the bed shows...  13. The mark on the bed shows where the framerail will be in relation to the bed. We cut off the excess material, leaving 2-1/2 inches of material for mounting.  14. The mounting area was...  14. The mounting area was cut into small sections and bent up to hold the tub in place.  15. This is the mounting area...  15. This is the mounting area for the base of the tub, and it was crucial that the edges be straight. We clamped a piece of angle to the edge and pounded it straight with a shoot-filled mallet.  16. Sliding the tub into position...  16. Sliding the tub into position was a little tricky. We nipped away at the ends of the mounting flanges we made on the bed to get the tub to slide into place.  17. With the tub in position,...  17. With the tub in position, the mounting flange and tub were drilled and Kliko fasteners were put in to hold the tubs in place until it was time for welding.  18. Thirteen-inch-tall tubs...  18. Thirteen-inch-tall tubs left us plenty of room for the meats at the stance we had in mind.  19. With the first tub successfully...  19. With the first tub successfully installed, we transferred the measurements from one side to the other and duplicated the efforts on that side.  20. Here you can see the finished...  20. Here you can see the finished product on one side and nearly finished product on the other. Transferring the measurements and reduplicating the work step by step gave us symmetrical tubs.
Billet Specialties
500 Shawmut Ave., Dept. SC
La Grange
IL
60526
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Summit Racing Equipment
P.O. Box 909
Akron
OH
44309
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Dynatrac
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Hoosier Racing Tire Corp.
65465 U.S. Hwy. 31
Lakeville
IN
46536
219-784-3152
219-784-2385
www.hoosiertire.com
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Sleeper Suspension Development
La Verne
CA
909-392-8886
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Reider Racing Ent. Inc.
12351 Universal Dr.
Taylor
MI
48180
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