[Skittles]

Hi guys, I have a hacked to pieces 4x4 Isuzu bighorn/trooper (Holden Jackaroo). Its old as the hills and seems to have an extremely uncommon engine in it (UBS13, G200z petrol 2L)

It is a manual transmission, with a manual selecting gear stick for 2, 4H and 4L. It also has manual lockers.

The problem I'm having is it doesn't seem to be going into 4x4 no matter what I select. I can feel a small crunch when going into 4H or 4L. but its simply not engaging. Now I have been looking at forums for a week now trying to find useful information. I have come across many regarding SOTF vacuum issues etc. However after comparing all of those photos and walkthroughs, I'm confident my truck is too old to have this system. I also get no 4x4 light on the instrument cluster. Although I don't even know if I should have one as its quite an old model.

This thing has had a HAAAAAARD life. It also has about half the wiring chopped out of it.
If anyone could give me any info on parts to check, or perhaps any information on how to hardwire/bypass solenoids to make it always engage 4x4? (it never sees any roads)

Any help or ideas are appreciated.

 

[Enemigo]

Whoa! Tag for a follow on this thread.

 

[turnerd]

Goodness, you weren't kidding about it having a hard life.

The transmission behind that G200 should be an MSG4. Unless someone has retrofitted it (I have no idea how they would do such a thing) there is no SOTF on that Trooper. You likely broke a gear in the transfer case. You basically have to pull the transmission apart to fix it as the transfer case is an integrated unit. You can easily verify it is the transmission by getting all four wheels off the ground and seeing if the transfer case will spin the front prop shaft. I will mention that this method can tell you if the transfer case is messed up, but can also give a false positive result as many transfer case issues only show up under load (meaning you will have to get it stuck in 2H).

 

[Skittles]

Goodness, you weren't kidding about it having a hard life.

The transmission behind that G200 should be an MSG4.

Thanks for the reply. The gearbox is factory. So I’m off to a good start there. I’ll jack it up either tomorrow or on the weekend and see if the front wheels spin when I have 4x4 engaged and accelerating. I’ll get back to you.

just out of curiosity. Does anyone have a workshop manual? Or do you know if anything electrically needs to be plugged into these gearboxes? Solenoids? Anything that may have been cut or missing? (As about half the wiring in this thing is cut, i purchased it all like this)

 

[mudoilngears]

There is nothing aside from the shifter itself that influences engaging 4wd. Is the vehicle running?

 

[Skittles]

There is nothing aside from the shifter itself that influences engaging 4wd. Is the vehicle running?

Yes. The vehicle is running. But it seems to get stuck in rocks and only the rear wheels are spinning.

 

[Shawn Anthony]

In the USA this type of vehicle is known as a Truggy. A cross between a truck and dune buggy.

The 4x4 light on your dash is turned on by a mechanical switch located on the side of the gear box. I would simply assume that the switch and/or the electrical for it is broken. Even so, working light or not it will not affect the operation of the 4x4 drive system.

The later second gen troopers/jackaroos featured a shift on the fly 4x4 system that requires a vacuum actuator to engage or disengage the axle.

The first generation Troopers/Jackaroo had two different four-wheel drive systems which function almost exactly the same. They're both fully mechanical drive systems and require the vehicle to come to a full stop before shift from two-wheel drive to four-wheel drive. The only difference between the two systems is the 87(?) and up had Auto locking hubs to disconnect the front wheels from the axle. This is so in two-wheel drive mode your axle and front drive shaft do not spin. This increases your fuel economy and prevents unnecessary tire wear.

Your early model Trooper/jackaroo front axle is permanently fixed. Regardless if you're in two-wheel drive or four wheel drive your front drive shaft and axle rotates.

EDIT: first gen troopers had 2 different types of auto locking hubs. The earliest type are made by Aisian and later years used Isuzu own inhouse designed locking hubs. The Aisin hubs are much larger than the Isuzu hub.

Aside from a broken differential, a broken or missing front drive shaft & a stripped hub drive flange..which is rare to find.... you're looking at three possible reasons why your four wheel drive is not engaging.

#1 Your transfercase is not shifting from two Wheel to four wheel drive. .

#2
You have a broken CV joint.

#3
The tip of the axle shaft is broken off inside the hub.

My best educated guess of what is wrong would be possibility number two and three.

 

[mudoilngears]

The only difference between the two systems is the 87 and up had Auto locking hubs to disconnect the front wheels from the axle. This is so in two-wheel drive mode your axle and front drive shaft do not spin. This increases your fuel economy and prevents unnecessary tire wear.

How do free wheel hubs, whether auto-locking or manual, affect tire wear?

 

[Shawn Anthony]

How do free wheel hubs, whether auto-locking or manual, affect tire wear?

When the front tires spin the 4 front CV joints, axle shafts, carrier assembly, ring & pinion, driveshaft all the bearings plus flinging all that gear oil adds rotating mass and friction. When turning the steering wheel the CV joints bind some which adds even more friction to the system. Simultaneously the spider gears requires added differential force for the action to function. All this added mass & load prevents the front tires from spinning freely as they should. Contributing to unnecessary treadwear and lowering fuel economy.

Evidence of this can easily be noticed with any part time 4x4 vehicle with locking hubs/axle system. With the front axle locked and in two wheel drive mode the vehicle turning radius is large and doesn't like to make a u-turn because of the added mass and friction is preventing the wheels to spin freely therefore the tires slides and slip which creates unnecessary treadwear.
Disconnecting the front axle in two wheel drive and there is a significant difference in turning radius. The vehicle doesn't feel as if it doesn't want to make this u-turn. You will also notice it requires less engine power to carry the vehicle through the turn.

 

[mudoilngears]

Yes. The vehicle is running. But it seems to get stuck in rocks and only the rear wheels are spinning.

Are your hubs engaged?

 

[Skittles]

Are your hubs engaged?

Yes. They are set to lock. I actually appreciate the simple questions. Just in case I’m missing something.

 

[mudoilngears]

Unlock the hubs, put it in either 4H or 4L and have someone watch as you drive, to see if the front driveshaft turns and that one of both of the CV shafts turn.

 

[Skittles]

In the USA this type of vehicle is known as a Truggy. A cross between a truck and dune buggy.

The 4x4 light on your dash

Fantastic info. Thank you. I’ll jack it up on the weekend and look it all over. A CV joint or issue in the hub is entirely plausible. Sadly so is the transaxle. I’ll get back to you.

 

[Shawn Anthony]

Fantastic info. Thank you. I’ll jack it up on the weekend and look it all over. A CV joint or issue in the hub is entirely plausible. Sadly so is the transaxle. I’ll get back to you.

Welcome...
I think it's important to add that first gen Troopers/jackaroo used 2 different auto locking hubs.. The US didn't have the trooper until 1984. So I can't say when this changed was made. The earliest type are made by Aisian and later years used Isuzu own inhouse designed locking hubs. They look completely different from one another.


If your hubs look the one in the photo, you do have Aisin auto locking hubs. Testing for proper operation of both sides will need to be added as possible cause of why your 4x4 is not working.

 

[turnerd]

Welcome...
I think it's important to add that first gen Troopers/jackaroo used 2 different auto locking hubs.. The US didn't have the trooper until 1984. So I can't say when this changed was made. The earliest type are made by Aisian and later years used Isuzu own inhouse designed locking hubs. They look completely different from one another.


If your hubs look the one in the photo, you do have Aisin auto locking hubs. Testing for proper operation of both sides will need to be added as possible cause of why your 4x4 is not working.

View attachment 127488

The USA models got the Aisin auto locking hubs as the only option from 1984-1987. In 1988 with the introduction of the 10 bolt front axle and hub redesign, Isuzu went to their own auto locking hubs and Aisin manual locking hubs for the newly introduced automatic models. The Isuzu autos came on all vehicles except the 4-cylinder automatic until the end of the first gen Trooper in 1991. From then on it was only Isuzu autos on traditional transfer cases and drive flanges on the SOTF systems.

 

[Shawn Anthony]

The USA models got the Aisin auto locking hubs as the only option from 1984-1987.

i never had the time to confirm. Looks like you nailed down. Thanks for that information.

 

[Skittles]

In the USA this type of vehicle is known as a Truggy. A cross between a truck and dune buggy.

The 4x4 light on your dash is turned on by a mechanical switch located on the side of the gear box. I would simply assume that the switch and/or the electrical for it is broken. Even so, working light or not it will not affect the operation of the 4x4 drive system.

The later second gen troopers/jackaroos featured a shift on the fly 4x4 system that requires a vacuum actuator to engage or disengage the axle.

The first generation Troopers/Jackaroo had two different four-wheel drive systems which function almost exactly the same. They're both fully mechanical drive systems and require the vehicle to come to a full stop before shift from two-wheel drive to four-wheel drive. The only difference between the two systems is the 87(?) and up had Auto locking hubs to disconnect the front wheels from the axle. This is so in two-wheel drive mode your axle and front drive shaft do not spin. This increases your fuel economy and prevents unnecessary tire wear.

Your early model Trooper/jackaroo front axle is permanently fixed. Regardless if you're in two-wheel drive or four wheel drive your front drive shaft and axle rotates.

EDIT: first gen troopers had 2 different types of auto locking hubs. The earliest type are made by Aisian and later years used Isuzu own inhouse designed locking hubs. The Aisin hubs are much larger than the Isuzu hub.

Aside from a broken differential, a broken or missing front drive shaft & a stripped hub drive flange..which is rare to find.... you're looking at three possible reasons why your four wheel drive is not engaging.

#1 Your transfercase is not shifting from two Wheel to four wheel drive. .

#2
You have a broken CV joint.

#3
The tip of the axle shaft is broken off inside the hub.

My best educated guess of what is wrong would be possibility number two and three.

Thank you very much. Jacked it up to check it all over on the weekend. Have a broken drivers side CV joint. I can see the half connected to the axle working. But where it connects into the wheel it’s not spinning at all. Ordered a new part. Will be here in a few days. Just want to thank everyone in the thread for their suggestions. Information and help.