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Currie F9 Rear End - Burly Backend
Currie Enterprises' F9 Custom Rears Can Handle Some Serious Power.
Oct 1, 2010
Corona, CA 92880
Chicago, IL 60609
Cleveland, OH 44114
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Currie F9 Rear End - Burly Backend
Here is the center of the F9 rearend that Currie designed and built. The housing body is built out of 3/16-inch Hi-Form steel, while the third member face is 3/8-inch thick Hi-Form steel. Inside you will find gussets to provide more strength to the third member face and bulkheads to add more support for the axle tubes. The F9 provides 3 inches of tube engagement as well, way more than any stock 9-inch housing.
Here is a look at the gussets used to strengthen the third member face.
Like we stated in the opening text, Currie builds the F9 from scratch, so the axle tubes start as 3-inch DOM tubing that is rough cut with a band saw. For an even stronger rearend Currie offers chrome-moly tubes and housings.
Then the tubes are chucked in a lathe where they are cut to the perfect size. The inner diameter is opened up so the large bearing ends will slide in.
One key feature to adding durability to the complete unit is how Currie indexes the axle tubes into the housing to prevent them from twisting.
Here you can see where the flat part that was just cut in the tube indexes into the F9 housing. Once welded, it will be nearly impossible to twist the axle tubes.
Another area that is unique to the F9 is this inner bulkhead that provides another area of support to the axle tubes.
Because it was getting pretty difficult to find bearing ends off of original rearends, Currie has new ones cast off site before they are machined. These are the large bearing or Torino-style ends which use standard seals and bearings so you can get parts from your local parts supplier, or Currie of course.
With the housing in a fixture and a mock-up third member and axle in place, the tubes and bearing ends are trued and set to customer specs.
Once everything checks out, the tubes and ends are tacked in place.
Now the housing is moved to the welding room so all the components can be fused into one beefy unit. Here, the inside end of the axle tubes are welded to the bulkhead.
At this point any accessories are attached as well like these leaf spring perches. These are 3/16-inch thick and will work with our multi-leaf pack. Currie also offers pads for mono spring applications as well.
Now that the housing is all welded together, it is put into another fixture and trued up with a press. With the amount of welding that was performed, things are bound to move a little. After straightening, the housing is put into a Steelabrator Airless shot machine. This removes all scale and other contaminants, inside and out, for a super clean product.
The third member will be assembled using Currie's 9+ Race Gear case, 9+ nodular iron yoke for a 1350 U-joint, and 9+ Big Bearing pinion support. Also in the mix is the 3.70:1 gearset from Motive Gear and the Detroit TrueTrac diff. The 9+ case is a completely redesigned piece that has all kinds of improvements built into it to provide more strength and support to the ring and pinion.
Step one is to join the ring gear to the TrueTrac differential with the new hardware. The ring gear is a tight fit so it is pulled on using the bolts and an impact gun.
The pinion support is temporarily assembled with a different yoke and bolts, then installed into the gear case. The new yoke will be installed after the gear lash is set up.
Now the diff assembly is lowered into the third member and held in with the stronger designed billet steel caps.
Gear lash is set with a dial gauge. Currie builds so many of these that the technician got it right on the first try.
Since the gear engagement was spot-on, the screw-in side adjusters were locked in place with these bolt-on tabs. This will prevent the adjusters from rotating and allowing the gears to come out of adjustment.
After another round of checks the caps are torqued down.
Now the temporary yoke and bolts are replaced with new parts. Again, Currie not only manufactures the housing and what not, but it also has stronger hardware made specifically for the rearends.
After a quick coat of paint to prevent rust, the third member is bolted to the housing. A new gasket and a small bead of silicone are used to create a leak-free seal.
The axles start out as raw 1541 forgings that have been induction heat-treated. They are quickly trimmed close to our spec with a chop saw.
After the cut end is perfectly sized and the end chamfered on a lathe, they are placed in a grinding machine that cuts in 35 splines.
The next CNC machine drills the lug pattern 5 on 4 3/4...
...with 1/2-inch studs in our case.
A very large press is used to install the studs and the bearing assemblies. The bearings used are Timken set-20 tapered roller bearings.
The axle assemblies are slipped into the fresh case and held in place with stronger Currie-made retainer plates.
With that, the rearend was ready to ship out to Jim so he could add his Wilwood brakes and fill it with 84-140w non-synthetic gear oil. This point is very important as Currie has done extensive research and found the synthetic fluids don't provide enough protection under extreme loads. In fact, using synthetic fluid will void any expressed or implied warranty on Currie products. We will revisit this rearend when Jim gets it under his Nova and takes it to the track.
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