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Transitioning from Subaru

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Transitioning from Subaru

Postby jiranz5 » Mon May 22, 2017 1:04 pm

Hi All,

For many years, I’ve had the joy of driving Subaru’s around. They’re small, lightweight and that symmetrical AWD system works really well. There have been times where those Subaru’s have outperformed bigger SUV’s. Unfortunately, they’re also small and lightweight:

• Small – yeah… that forward angled rear pillar makes it impossible to get the kid in and out of the car. Then try fitting her cousins in the back, all their gear and the dog too.
• Lightweight – Having a wife and 2-year-old daughter who are prone to car sickness does not go down well. In fact, it comes up… a lot.

So out with the smaller family wagon and in with the new. Couldn’t afford one of the later model Subaru Foresters with extended leg room, so had to look at alternative vehicles. Que the 1996 Isuzu Wizard.
I knew a little bit about the Wizards since my brother had previously owned a 1999 model with all the problems associated with that engine. Knew the 4JG2 was a good motor and figured at 280,000kms it had a reasonable amount of life still left in it. Also figured there were key maintenance items about due (such as the alternator) which have proven true so far. The thing that I wasn’t expecting was the 4wd performance, or lack thereof.
We have 12.5 acres of land with a creek that runs through the middle of it. On the far side of this creek is a bank that I have driven up many times in the Outback and also in Foresters in many weather conditions. It’s approx. 30% incline with a clay base. Short story is, I could not get the Wizard up that slope. It crabbed sideways on me every time the front wheels reached over the top and the rear could no longer find traction in the clay and I’ve lost confidence in the vehicle. Since then I’ve been spending a bit of time on Google trying to understand how the 4wd system works on my Wizard and how to can adapt my driving accordingly. The conclusion being that Subaru’s ‘point-and-drive’ system must have made me a lazy ‘off roader’. I’m finding myself in a whole new world and the biggest issue is there’s too much information not specific to my vehicle. Apparently, LSD’s on the front and rear were optional factory extras and I have yet to learn whether my vehicle has them or not. I’m also finding myself prejudiced by my knowledge of Subaru AWD systems.

Google’s abundant knowledge suggests that when I engage 4L on the lever, that it locks the drivetrain front-to-back. What happens after this on my Wizard and what would I need to do to my vehicle to make it up a simple embankment that my old Outback (on road tires) went up no problem?
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Re: Transitioning from Subaru

Postby geeves » Mon May 22, 2017 4:32 pm

First thing off road is always the tyres but the chances are the Subaru and Wizard are running similar tyres. Second thing is momentum The Wizard is 500 or so kg heavier so if traction is lacking needs a little more pace at the bottom. Third thing is keeping the wheels on the deck which the wizard is pretty good out of the box but in all but extreme conditions so is the Suby The subaru hasnt got the total articulation of the wizard but what it does have it uses pretty efficiantly.
Subaru also has a viscus center diff which does reduce traction in most conditions but in supper slippery stuff like ice or wet clay can work amazingly well.
One thing you do need to check on the wizard is whether the 4wd system is working correctly. With the engine idling engage 4wd the light should come on steady. Then leaving the engine idling and in 4wd neutral gear chock the back wheels then lift each front wheel one at a time Try and turn the wheel. If you can investigate why
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: Transitioning from Subaru

Postby jiranz5 » Sun May 28, 2017 8:49 am

Thanks Geeves. I did your test yesterday afternoon and no I couldn't turn them. Does that mean I have a front differential or was I working against the rear?

I also had another go getting across the creek by increasing momentum but as soon as lost traction on the rear I lost momentum and started crabbing sideways. Didn't like the lack of control so tried the "traction control" method of lightly applying the brake while crawling up and it went straight up no sweat. Yay for YouTube 4wd lessons :).

My downhill approach was slightly different and I just caught the right-side running board on the ground. My guess is a slightly longer wheelbase than the Subarus? As my speedo is currently out by 13% (reading 100kmh but actual 87), I was thinking of putting a bigger sized tyre on. What could I reasonably go to without worrying about lifts at this stage? Theoretically I could reduce that to speedo misread to 6% by putting 265/75/16's but people on here seem to have 2" lifts to achieve this. That's in increase in width of 10mm each side, +25mm radius and 7.02% increase in rolling diameter. I did the whole tape measure thing and looks like it might fit but there must be someone here who knows for certain.
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Re: Transitioning from Subaru

Postby geeves » Sun May 28, 2017 4:00 pm

Dont know why your speedo is out that far Mine was nowhere near that bad on standard tyres. 265/70 16 certainly fit no issue, 75s should just fit. A standard suspensin lift is 2 inch so thats what everyone uses
The front diff check sound spot on. If you had lifted both wheels with the car in 4wd you would of been able to spin one tyre and the other would of rotated the opposite way There is a dog clutch in the front diff that controls 4wd/2wd. This is what we were testing
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: Transitioning from Subaru

Postby jiranz5 » Fri Jun 09, 2017 7:57 am

I've been trialing the DigiHUD app on my Android phone for the past couple weeks and the GPS based Speedometer has been accurate within 1km over 3 vehicles. Based on the most conservative reading, the Wizard's actual is 93km/h at 100km/h. That's approx 7.5% over-read so the 265/75/16's would pretty much correct this. I should note that my original reading or 87 km/h was based on those electronic speed indicators you drive past on the State Highway - which it turns out are quite inaccurate.

I came across this calculator http://www.advanced-ev.com/Calculators/TireSize/index.html when looking into diff systems, but i can't be using it right as it shows my differential as 3.5. As far as I can tell, these vehicles don't come with that option. Maybe overdrive is messing up the calculation? My variables were:

Engine RPM: 2,500 (it sits a needles width under this at 100km/h on the speedo)
Tire Diameter: 29.5 inches
Speed: 62.5 MPH

equals Differential Ratio: 3.512
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Re: Transitioning from Subaru

Postby jiranz5 » Fri Jun 09, 2017 8:27 am

I think I just answered my own question.

Engine RPM: 2,490
Tire Diameter: 29.3 (due to wear & tear)
Speed: 62.5 MPH
Equals Differential: 3.47

Assuming 3.47 is actually what people call Final Drive and divide this by 0.723 for the Overdrive ratio based on Wikipedia https://en.wikipedia.org/wiki/GM_4L30-E_transmission
This gives a diff ratio of 4.8

I might have to follow this YouTube guide for fun just to confirm https://www.youtube.com/watch?v=RNgjS5mHI0E. Should be 24/5 ratio if it's a 4.8?
jiranz5
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Re: Transitioning from Subaru

Postby geeves » Fri Jun 09, 2017 10:16 am

Not confirmed your sums but will say that unless someone has swapped your diff it will be 4.3. Only choices are 4.3 and 4.56 (there is a 4.8 in theory but only one has ever been verified in the wild)
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: Transitioning from Subaru

Postby jiranz5 » Fri Jun 09, 2017 11:56 am

It will be interesting to see what the results are from the physical check above. The ratio calculater here http://www.boosttown.com/gearbox_differential/speed_calculator.php also suggests a 4.8 diff. Unless there's another differential in the drivetrain somewhere? Either that or my tachometer is munted.

Image.

Guess we'll have to wait and see.
jiranz5
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Re: Transitioning from Subaru

Postby geeves » Fri Jun 09, 2017 12:11 pm

Try lifting 1 back wheel and rotate through one turn while counting the no times the driveshaft turns. Divide the answer by 2 for your diff ratio. It will be either 4.3 or 4.5. My 2 cents is on 4.3 as 4.5 was not a factory option in these although those revs point that way. If it does turn out to be 4.5 try driving in a straight line on a hard surface in 4wd. 20 meters will answer this. Is the trans binding? If it is we need to check if the ratios are the same. Mismatched diffs could cause your handling issues
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: Transitioning from Subaru

Postby jiranz5 » Mon Jun 12, 2017 6:47 am

10x turns of the wheel = 21.5x turns of the driveshaft. 21.5 x 2 = 43 which / 10 = 4.3. So it's definitely a 4.3 on the rear.

Went to Dunedin yesterday so can confirm 3,090 RPM @ 100km/h in 3rd which is supposed to be 1:1 ratio on the Gearbox. This calculates @ 4.3 ratio also. Guess the overdrive (4th gear) ratio must be .813, not the .723 as recorded on Wikipedia.
jiranz5
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Re: Transitioning from Subaru

Postby geeves » Mon Jun 12, 2017 12:03 pm

I havnt got the book handy but .8 sounds more correct. The problem with wiki is that there are many variations of this car and Wiki's version could be the American Rodeo which for some models had a chevy engine and box
Sanding your knuckles before starting work can help. That way you cant skin them
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