By Christian Sturtz, [email protected]
Photos by Christian Sturtz
I love the JT Gladiator platform. It does everything I need it to, but with my recent addition of 37” tall tires, my mileage has dramatically decreased. I used to get 15-16 mpg, and with the 33” tall tires and 4.10 stock gears, I was relatively happy with the mileage. The 37” tall tires knocked my mileage down to 12 mpg, and I decided something had to change. I recently regeared a JL to 5.13 gears, and the mileage on that vehicle is consistently 15-16mpg. The JL is so loaded down that I knew if I regeared my JT, I could get close to that, if not better.
A slight side note: up until the recent adoption of the Jeep’s 8-speed automatic transmission, a Jeep with an automatic would not be enjoyable with stock 4.10 gears and >37” tall tires. When I say not enjoyable, I mean the Jeep couldn’t even get out of its own way – constantly hunting for the right gear with no power, leading to overheating, stressed parts, and causing premature wear or failure of parts. Then came the 8-speed automatic, and it is a game-changer! This thing is dialed. Besides having poor mileage and rarely shifting into eighth gear (even on the highway), it drives great – it has plenty of power and never hunts for gears.
With all this in mind, I wanted to regear the JT to 5.13 gears and add some differential protection. I occasionally go down to the local Jeep dealership and snoop around. While down there, I noticed a front Rubicon housing laying out. I asked some questions, and they said they ordered it for a customer having axle disconnect problems- this was ordered before the parts were available separately, so they ordered a complete housing to take care of the customer’s needs. I asked if they were willing to sell it, and they agreed, and we had a deal. (Figure 1)
Yukon Gear and Axle has a wide selection of gear options for most makes and models. They set me up with front and rear 5.13 gear sets, master install kits, and their hardcore differential covers. I started in the rear by removing the tires, unhooking the drive shaft, draining the axle (by removing the cover), and removing the brakes. The axles were then unbolted and removed. With the cover off, I unhooked the electrical connector, made sure the bearing caps were marked, and removed them. I used a large indexing prybar to pry the carrier out while being conscious of the wires and workings of the locker. These late-model Dana axles shim on the outside of the carrier bearings. Normally, you would have to mark their position, but due to their differing sizes, this is not necessary. (Figure 2)
From the front side, the pinion nut was removed, and yolk was pulled off with a 2-jaw puller. The pinion nut was screwed back on and I used a socket to tap the pinion out. I used a Yukon seal puller to remove the seal. Then, the outer bearing and slinger was lifted out. A brass punch was used to knock both inner and outer races out. (Figure 3) *Tip: there is a pinion depth shim under the inner race be careful not to hit the shim directly and damage it.
Before putting anything back in, I fully cleaned the housing. I used a differential bearing puller to pull the larger carrier bearing off. The locker control side is a different story. The clam shell style puller just wouldn’t work. So, I had to bust the cage on the bearing and remove the rollers. Then, I used a bearing splitter and 2-jaw puller to remove the inner race. With the inner race removed, the magnetic sensor can be slid off to remove the ring gear. The ring gear bolts were removed, and the ring gear was knocked off. Before installing the new gear on the carrier, I de-burred the gears and cleaned up the mating surfaces. I like to press one of the bearings on and use the press to hold the carrier while I tighten the ring gear bolts to 135 ft/lbs. *Tip: the carrier bolts come coated with thread lock sealant, but I still suggest using additional red liquid thread lock. The carrier was then flipped over, the electronics were slid back on, and the control side bearing was pressed on. The pinion bearing was then pressed onto the pinion. Make sure the bearing is all the way seated, and use a large enough tube that you do not press it onto the pinion. (Figure 4)
I started the housing reassembly by driving the races in the front and rear, making sure to remember the pinion depth shim underneath the inner pinion race. The outer pinion bearing and slinger were set in the front of the housing, and the seal was driven in. A few dabs of grease to ensure the spring won’t get knocked off during installation. With the new crush sleeve installed, the pinion was slid in. *Tip: I have found that if you use the old crush sleeve along with a big washer, you are able to slide the bearing onto the pinion enough to get the yoke on and start the nut. The pinion nut was tightened until there was no play in the bearings, and a pinion pre-load of 12-19 in/lbs was reached.
Yukon gears normally set up well, and these were no different. I first installed the carrier with the stock shims, driving them in with a Yukon shim driver. The stock shims did not provide enough backlash, so I used the included shims to make up some packs that moved 0.005 from one side to the other. This is all it took, one shim move, and I had the 0.006-0.0010 backlash. I re-torqued the bearing caps to 70 ft/lbs and ran a quick pattern on the gears with marking compound. The pattern looked great, so I put the new Yukon hardcore cover on, finished the assembly, and filled it with gear oil. (Figure 5). Before swapping the front axle, I wanted to add some lower control arm mount protection. MetalCloak makes some great weld-on skid plates to do just that. This turned out to be a quick endeavor with the axle out. I prepped the surfaces, tacked the skid plates into position, and burned them in.
The original front end was removed. It was necessary to press out the Johnny Joint upper bushings that I had installed and transfer them to the new housing prior to the installation of the new axle. The only major difference I noticed on the Mojave and Rubicon housings was the shock mounts. RockJock had specifically designed shock spacers for the Mojave that are not compatible with the Rubicon shock mounts. This required me to rework the mounts. (Figure 6)
Front gears are almost the same exact setup as the rear gears, so I won’t go into detail on this; I will just highlight a few points. Be careful with the setup, especially installing the carrier and checking the pattern- make sure to have the keeper on the magnet side of the locker. This might not always rotate, but it can, and without the keeper, it will wreck stuff. Also, if you are switching from a late-model axle without a locker to one with a locker, the axle shaft lengths are different. This is due to the positioning of the center pin on the carriers. I didn’t realize this and had to buy a new driver’s side shaft and intermediate shaft on the passenger side. (These part numbers are included in my part listing.) The wiring for the locker is super easy; Chrysler has made a harness with the two wires required for the electromagnet- I wired this into my last remaining auxiliary switch on the Mojave’s dash. Even though there was some additional cost, I am super happy with the end product. I have a factory-front locker in a Mojave! It will hopefully be more fun to drive and easier on my wallet.
Parts Used:
Yukon
Front 5.13 Gears: YG D44JL-513R
Rear 5.13 Gears: YG D44JL-513
Front Master Overhaul Kit: YK D44JL-FRONT
Rear Master Overhaul Kit: YK D44JL-REAR
Front Cover: YHCC-D44JL-FRONT
Rear Cover: YHCC-D44JL-REAR
MetalCloak
Lower Control Arm Skids: 7698
Chrysler
Harness: 7707 2413-001
Drivers’ Complete Axle: 6847 7137AA
Passenger Intermediate Axle: 6840 0416AA
Sources:
Yukon Gear and Axle
RANDYS WorldWide Inc.
10411 Airport Rd. (Ste 200)
Everett, WA 98204
1-206-317-4736
MetalCloak
2484 Mercantile Dr.
Rancho Cordova, CA 95742
1-916-631-8071
