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Rear Axle Wrangling - Currie F9 Axle - Jp Magazine

Pete Trasborg Brand Manager, Jp

In last month's issue, we hemmed and hawed about what axle we should put in the back of our '01 Wrangler. It isn't an extreme rig-we use it for daily driving and weekend warrior type of stuff. We want to be able to go out wheeling on the weekend and have the peace of mind that it will get us to work come Monday.

2001 Jeep Wrangler Tj Currie F9 Axle comparison Photo 29243191

Currie Enterprises offers powdercoating for its axles, but once you start scraping the axle over some off-road obstacles, good luck fixing the damaged powdercoating. We took the company's suggestion and painted our axle with some semi-gloss Rustoleum Stops Rust. Looking inside the F9 housing, the studs are threaded-into the 3/8-inch-thick face and then double-nutted from the back for the ultimate in retention. No problems with them pulling out, spinning, or pressing back in when you put the third member in. The stiffener plate and triangular welded-in reinforcements provide additional strength to an already strong housing. Due to the design of this housing, we think that only the most abusive will need the optional add-on truss.

We decided that the Dana 60-based options were total overkill for our application, and since we'd already mangled a TJ Dana 44, we wanted something a bit stouter than that. We came down firmly in the Currie Enterprises camp with one of its F9 housings and outfitted it with sensibly-priced options to keep overall costs down.

The one thing we did spring for was the ARB Air Locker. Some of us would rather not run an automatic locker in a daily-driven Jeep, and because of that, the ARB was chosen. Sure, it is the single most expensive part in the whole rearend build, but in our opinion, well worth it in a dual-purpose vehicle. We went with a regular low-pinion 9-inch third member, lower-tier gears, and plain-Jane drum brakes, which allowed us to reuse a lot of our stock stuff on the install.

2001 Jeep Wrangler Tj Currie F9 Axle bolts Photo 29243194

We discuss how the formed 3/16-inch-thick steel housing increases ground clearance and how the F9 is way stronger than a stock 9-inch housing. But following our axle through the buildup gave us a better understanding of the improvements, and we picked up some tips and trivia to share with you along the way.

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We went to Randy's Ring and Pinion and picked up the budget-oriented Standard Gear 4.56 ring and pinion and master install kit. The company cautioned us that we might hear some gear noise out of this set of gears, but we figured we'd never hear it over our tires. We went with an ARB Air locker so that our short-wheelbase Jeep was still drivable on road day-to-day, but has spool-like traction when we need it. The Jeep already had the compressor and solenoids from a previous ARB install, so it was a slam dunk for us.

For any ARB installation you will need to drill a 1/2-inch hole for the bulkhead fitting. Normally that hole is in the top of the housing, but on the 9-inch axle, that fitting ends up pointing to the front of the Jeep. On a TJ, the rear sway bar is tight to the front of the housing, but the expert installer at Currie placed the bulkhead fitting perfectly and we had no troubles with sway bar interference later.

Last month we mentioned that this housing is available with monster-sized axletubes for abusive drivers. Our housing uses the more common 3-inch tubes, but the larger housing below (normally used for trophy trucks) will take from 31/2- up to 4-inch axletubes. The arrows indicate where the tubes are welded both inside and outside of the housing, which spreads the load out and resists bending. The vent line is put into the cavity between the reinforcement plate and the end of the housing to keep gear oil out of it.

PhotosView Slideshow The master setup kit we received from Randy's Ring and Pinion included a smaller outer pinion bearing (right). We failed to tell them we had a large bearing third member, so it was our fault. Of course, Currie had the larger Daytona bearing on hand (left).

The master setup kit we received from Randy's Ring and Pinion included a smaller outer pinion bearing (right). We failed to tell them we had a large bearing third member, so it was our fault. Of course, Currie had the larger Daytona bearing on hand (left).

The air piston for the Air Locker rides on the opposite side of the carrier from where the bulkhead fitting was installed. Some grinding was needed to make our carrier clear the third member. ARB designed the carrier to be as big and strong as possible within the confines of the 9-inch case, and we are told that this is not an uncommon occurrence.

Currie has a third member "dyno" in-house. This optional service brings the new third member up to full operating temperature, allows for break-in of the new gears, and provides a check for noise before a new rear-end is shipped out. Anywhere under 103dBs at highway speed is too low to hear in a Jeep, and our gears were at a paltry 99dBs.

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We were happy with our choice with regard to gear, housing, and axleshaft strength, but the lower pinion of the 9-inch gave us some concern. We went with a short yoke and U-bolts to fasten the driveshaft. The pinion is 3/4-inch lower than the Dana 44 we replaced, and we plan on smaller tires which can bring the pinion almost 2 inches closer to the ground. We went with a James Duff Enterprises 1/4-inch thick Duff Diff Protector to help keep the pinion out of harm's way.

Unlike many 9-inch skidplates that attach only to the pinion support bolts, this attaches to the pinion support and third member case bolts for more strength. It also provides a smooth bottom to slide over rocks. It is intended for the early Bronco 9-inch, so we had to grind the pinion mount until it fit-but it cleared our F9 housing just fine. However, we lost about an inch of under-axle clearance and it illustrates how the formed F9 housing provides more ground clearance than a stock 9-inch. If it hangs us up too much, we'll cut and weld that section of the skid for more ground clearance.

PhotosView Slideshow

First the housing gets tubes pressed in, cools, and is checked for straightness. Then it gets the mounting brackets welded on and is checked again. Finally, it meets the assembled third member, brakes, and axleshafts for final assembly and double-checking of dimensions. Note the heavy-duty 1/4-inch-thick brackets that allowed us to bolt this axle in place of our stock one with no problem at all. All bolt holes lined up just fine.

We had a set of cut-down F-150 axleshafts from another project that we planned on using, but it would have offset the pinion and housing too far for use in the TJ. The brackets are already pretty close to the F9 housing, so we went with the Currie performance axleshafts. Instead of disc brakes, we chose 11 x 21/4-inch drums that work with our stock brake lines and emergency brake cables. These drums require no modifications to the proportioning valve or master cylinder and provide better braking than stock drums.

We were able to re-bend and re-use the stock Dana 44 brake lines with the new housing. The TJ uses SAE flares which work fine with the drum brakes we chose. However, since the vent line on this housing was moved to the centersection, we had to lop the head off of a bolt and weld it to the axletube in the stock location to bolt the end of the flexible line back onto the housing.

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Rear Axle Wrangling - Currie F9 Axle - Jp Magazine

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