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Drivetrain Modifications


Manual Locking Hubs

My trooper came stock with Isuzu's own auto lock hubs. These hubs work well for most people and are easy to live with because you never have to get out in order to lock them. But I like knowing for certain when my hubs are engaged or not. So I decided to upgrade to manual locking hubs. I chose Warn premium hubs since they are a tried and true name and are very well built. The hubs are a direct replacement and are a very quick install.

Transmission Vent

During my engine swap I had the whole drivetrain removed from the vehicle. So while the transmission was on the floor I decided to address an issue with the Isuzu MUA5 Transmission. The transmission and transfer case of the Isuzu is an integral unit. They do not have separate cases that bolt together like most domestic applications. However the transmission and transfer case section do have separate lubrication and are separated by seals inside. However for some reason Isuzu vents the transfer case but not the transmission. Heat buildup inside the transmission can cause pressure to build and force fluid into the transfer case section which in turn causes the transfer rear seal to leak fluid. Isuzu's solution is to change to a different transmission seal. However this never addresses the pressure buildup. So most people with common sense would realize that venting the transmission is the real cure to the problem. So that's the approach I took. All that is required is the removal of a plug in the shifter plate and taping the hole with an 1/8" NPT tap and installing a barb fitting. Then you can run a vent hose to the engine compartment.


Transfer Case Vent

One other thing I decided to do was improve the vent for the transfer case as well. The stock vent is just a plastic breather cap. But if it ever gets submerged in water it can flood the transfer case. So I replaced it with a hose barb and ran a line up to the engine compartment just like the transmission. The transfer case vent does not get threaded in. I used a 3/8" pipe thread fitting and coated it in JB weld and the pressed it in until it seated and the let the JB weld harden. I could have relied on the press fit but the JB weld ensured it would never move and sealed it.

Safety Wired Hub Bolts

After running the manual hubs for about a year or so I noticed something interesting. Every time I used the hubs the bolts that hold them on would back off slightly. If I did not keep an eye on them the bolts would get quite loose. I could have used Lock-Tite but the hubs need to come off in order to service the wheel bearings and replace the brake rotors. I was concerned that if I did not use anti seize the bolts might break off in the wheel hub due to rust or corrosion. I needed a form of mechanical lock. Instead of spending big bucks on aftermarket parts I decided to go with some tried and true safety wire. In order to make this work I needed to pick up some bolts so I could drill all the holes before hand. One problem was that the area the bolts thread into is a tight fit. If the hole for the safety wire ended up against the side of the hub I would never be able to thread the wire through. So to combat that problem I drilled 6 holes around the perimeter of the capscrew bolt. This would make the task of threading the safety wire much easier. I also used stainless steel safety wire so it would never rust and look ugly. After a bit of time threading the wire through each bolt and twisting it nice and tight I had a permanent mechanical lock for all the hub bolts for no more than a few bucks in replacement bolts


Rear ARB Air Locker

For any four wheeler locking differentials, especially selectable ones, are number one on their wish list. Very few vehicles ever came with them from the factory and aftermarket ones are expensive. ARB Air Lockers are among the most desirable and most expensive. Any of the ARB units cost at least $1000 unless it is a very popular model. For Isuzu drivers the ARB units retail at around $1300 each. Once you have the units there is still some installation cost like bearings, seals and gaskets associated with them as well. With the ARB unit there is also the requirement of a compressor to actuate them.


I always had plans to get lockers some day but that was way in the future when I had $3000 free cash floating around. However, one day, mostly because I was bored I checked the classified section on and there was an add for an engine and lockers for sale. I took a look and the seller still had the lockers for sale. I made him an offer and we settled on a price of $1500 for the pair installed in their respective third members. It was a great deal for me but I was suspicious of the install work done by Independent4X. The seller warned me of a leaky pinion seal on the rear differential and said he had never used the front. When I got them home I un packed them for inspection and everything was just as the seller had described. You could easily see the rear differential had been leaking because it had oil residue all over the bottom side.
The seal replacement was a must for the rear differential and it also needed some cleaning. The front was free of oil but was still dirty on the outside. I took off the rear drive flange and immediately spotted the cause of the leak. The rear drive flange had deep grooves worn in it from the seal so there was no chance of it ever working. It was evident that Independent4X does not take the time to fully disassemble these differential units for inspection before selling them so I decided I better do it right and start from scratch on both units. So the front was torn down just like the rear. The front seal surface was in good shape, which is to be expected on a four wheel drive vehicle since it spends most of its time at rest. The rear unit was washed down to remove the oil and they were both taken in for sandblasting to get the cases in a like new condition.


After sandblasting both units were given a couple coats of engine enamel to keep them looking good. New drive flanges, oil seals and crush sleeves were ordered for both units. All the bearings were in very nice condition so them were left alone. The pinion preload had to be reset with the new crush sleeve so I made a tool at work to holt the drive flange steady while I torqued it to crush the sleeve then slowly apply more torque to the nut to dial in the preload on the bearings. An inch pound dial type torque is required for this step. The beauty about banjo style rear ends (Ford 9", Toyata and Isuzu) is that you only have to work with a small chunk when doing the gear setup and it is light enough to move on your own. No friend or hoist is necessary to move a 200+ pound axle around the garage. Once all the bench assembly was done it was time to move on to the actual install.
I picked a weekend and had my uncle come by for a helping hand on the install of the rear locker only, for the time being. The steps are pretty basic. Remove drive shaft, tires, brake caliper, axle retainer plate and slide out the axle about a foot from the tube. Now all the bolts can be removed that hold the third member to the housing. Here is a tip when trying to break the seal. Use a floor jack on the pinion flange and jack it up until your hear the RTV seal break open. Once that happens you can remove it by hand. Clean the mating surface, de grease, and apply new RTV. Then install the third member with the locker reverse of removal.


Once the heavy lifting was done the air line was run up the passenger side fame rail to the engine compartment. I chose a spot for the compressor right in the passenger side corner where the fenders meet the firewall. Space was tight but it was a great place to keep the compressor high and dry. I did contemplate installing it inside the truck but it makes an annoying sound and quite frankly can startle you when the pressure switch commands it on without you expecting it. I was in a Jeep once with the compressor in the cab and I did not like it at all. The compressor was easy enough to mount with the supplied bolts. The air line for the rear locker was plugged into its respective solenoid and then it was on to wiring. Simply put, ARB has a damn good harness. They even leave the body of the firewall connector off of the terminals so it is easy to pass through a grommet. My truck already had an existing harness right by the compressor so I just passed it through with some factory wires. Then all you have to do is plug all the loose terminals into the connector body and the harness is ready to plug together. Once you find a place for your switches you can run the switch wires and plug all of the wires in to their respective switches. The harness is designed with a kind of fail safe. The switches can only be activated in order. First you must turn on the compressor, that will send power to the rear locker switch so you can activate that only if the compressor is on. The rear locker switch will then power the front locker switch so you can only turn on the front locker once the compressor and the rear locker are on. The harness the requires you to supply a switched 12V source and a ground. Once all the hook ups were finished it was all ready to go. First time out everything worked flawlessly. No too bad for a bunch of used parts. Now I just need to set aside a whole weekend to tackle the front locker. That is going to require dropping the entire axle out of the truck so I will have to save that for later.

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