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1968 Camaro Currie Enterprises Drivetrain - Force Multiplier
We Take The First Step In Getting Our ’68 Project Car Back To Roller Status By Building A New Rearend At Currie Enterprises.
Jun 18, 2009
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Corona, CA 92880
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1968 Camaro Currie Enterprises Drivetrain - Force Multiplier
Because we’ll be running a Chassisworks g-Bar system under Track Rat, we decided to opt for their FAB9 housing as well. Since the housing comes with all the suspension brackets precision-welded in place it will be a real time-saver when we go to install the new suspension widgets. The mild steel case was ordered with late-model Torino housing ends.
The welding on the FAB9 is a work of art. Here you can get a better look at the lower arm bracket that will eventually support our g-Bar rear suspension. The multiple mounting holes will let us really dial in the Camaro’s handling.
We’ve always had great luck with Detroit Truetrac units, so we saw no reason to try something else. Its planetary helical side gears and pinions make this the perfect differential for a street car that likes curvy highways and the occasional road course. Under normal conditions the Detroit Truetrac performs like a regular open differential and, when required, automatically transfers torque to the wheel with the most traction. The Truetrac is capable of transferring up to 3.5 times more torque to the high traction wheel. This torque transfer ratio, called the bias ratio, is accomplished by using parallel-axis, planetary helical side-gears and pinions that mesh much like worm gears. Since the Truetrac uses hardened gears against hardened gears and not clutches or cones, there is nothing to wear out, so it won’t need maintenance. Eaton offers a preloaded and non-preloaded version for the 9-inch Ford. Because the preload helps the differential react faster, Currie offers it exclusively.
Next to building a manual transmission, putting together a third member has to be one of the more difficult items to assemble properly. It’s not impossible to do yourself, but it requires a few tools not normally found in the average roll-away toolbox. Items like a dial indicator, a bearing press, and a bearing puller are just a few of the unique tools you’ll need. Currie will completely assemble a third member, and set all the pre-loads and backlash for just $124.95. Doing it wrong can cost you a bunch of time and even more money, so we feel having a pro do it is well worth the extra cash. Besides, this way there’s a warranty.
With the bearings pressed onto the Truetrac, it was time to mate it to the ring gear. To keep everything in place, we dabbed a liberal amount of red thread locker on the bolts. Since we will be running an overdrive Tremec transmission we decided to go with 3.70 gears.
With the unit reassembled and spinning freely, Torres started adjusting the backlash. The goal for our unit was 0.010-inch.
With that done, Torres checked how the gears were meshing together using marking paint. We were off on the first try (high on the coast), but that’s common when trying to mate new parts to a reconditioned case.
Next, we pressed on the pinion support and checked the feel. According to Currie it should take around two to three pounds to turn. If it’s too tight, or too loose, it will eventually cause the pinion bearing to fail. Once Curry technician, Ruben Torres, was happy with the feel, he installed the blue pinion seal.
We then greased up and inserted the nodular iron yoke. We could have spent a little more money and gone with the fancy billet yoke, but the nodular iron version is more than capable of handling the power we plan on making. With the yoke in place, Torres, secured the pinion assembly to the Ford 9-inch case. Currie uses solid spacers instead of the original-style crush sleeves, so it’s easy to pull the unit apart and adjust if needed.
Since the backlash was up around 0.018, Torres used a custom-built wrench to adjust the spanner nut on the carrier unit until the dial indicator read 0.010-inch.
The pinion assembly was removed and a thicker spacer put in place. Sometimes they hit it on the first try, while other times it takes a few more attempts.
Currie was very eager to show us their new Cut-To-Fit (CTF) 9+ axles. They are offered in 26-, 29-, 32-, and 35-inch versions and have 4 inches of spline length. Up to 3 inches of this may be cut off so you can attain an axle length anywhere between 23 and 35 inches, and still have adequate spline engagement into your third member. They are 31-spline and feature high-performance induction heat-treated, forged alloy steel construction, 2.500-inch brake space offset, and 2.800-inch register hub diameter (making them ABCS - Aftermarket Brake Configuration Standard - compliant). Wheel bolt patterns are dual-drilled for five on 4.5-inch Ford and five on 4.75-inch Chevy, and an access hole is drilled. All CTF axles come with a full installation package which includes one set of five 1/2-inch Ford-style wheel studs, one set of five 7/16-inch Chevy-style wheel studs, one set 20 tapered roller bearings with race, seal, and collar, and one heavy-duty late-model large bearing style retainer plate.
We were then rewarded with the desired contact patch. Getting this right is the key to a long-lasting, and quiet rear assembly.
Lastly, we secured everything and torqued the pinion support and other fasteners to spec. Total cost for the third member, including the Truetrac diff, Ford case, 9+ Race pinion support, 1330 9+ yoke, and 3.70 gears was $1,336.20. That price even includes the labor to put it all together.
Rather than screw in studs, the FAB9 housing comes with 12-point ARP bolts. The problem is that it’s nearly impossible to get a ratchet on the head of the fasteners since they are right up against the inside of the case. Also, because they are 12-point you can’t use an open-end wrench. The toughest one was the bolt near the case’s magnet. We found the easiest way was to jam two nuts together and “pull” the bolt through the case
To cut our axles to the right length, we needed a few measurements. The first was the width of the housing from flange to flange. In our case this was a hair over 52.5 inches. You can also see that we had our FAB9 housing powder coated in smoky silver over at Embee Performance Coatings in Santa Ana, California.
We then repeated the procedure on the passenger side. This time our magic number was 21.625 inches.
The best thing about Currie’s CTF axles is that anyone with a chop saw and the right blade can whip out a set of custom axles in their own shop or garage. It sure beats waiting, and who doesn’t love instant gratification? Remember to practice the, “measure twice, cut once,” principal. With the axles cut, we then chamfered the edges on the grinder.
Currie had this sweet jig for double-checking axle length prior to putting everything together. They are looking for the axles to be less than 1/8-inch from the pin, but not touching. We have to hand it to Currie and their computer program. Our axles were the perfect length.
Next, we measured the driver side axle tube. The measurement is taken from the stud, as shown, to the outside of the flange. The distance worked out to be 20.875 inches.
These numbers were then plugged into this cool axle calculator available on Currie’s website. We also chose the appropriate backspace and rotor thickness for the Wilwood brakes we’ll be running. With that info plugged in the program, it calculated the exact length to cut our axles.
The bearings were pressed onto the axles, but we decided to upgrade to the much stronger heavy-duty retainer plates sold by Curry (PN CE-9005TW, $15.95 ea). Unlike the flimsy ones supplied with our brakes, these won’t deform under hard driving and will help keep the fluid where it belongs: inside the housing. The only downside is, since they’re not slotted, they must be installed before the bearings are pressed on.
With the axles done, we could drop in our freshly-painted third member. To seal the deal we applied a bead of black silicone, a gasket, and another bead of silicone. Lastly, the third member was secured in place with the appropriate crush washers and nylon nuts included with the FAB9 housing.
Here’s our finished rearend ready to be trucked over to Best Of Show Coach Works and stuffed under our Track Rat project car. Total dollar amount spent at Currie was $1,875 and the FAB9, with all the g-Bar brackets welded in place was $1,099. The total for everything came to $2,974.
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