Isuzu Trooper Owners Club UK™

[ianh]

Hi all
Can anyone explain how the shift on the fly system works?

I’ve seen the link to the web site  that gives a basic explanation http://www.autoworld.com/news/Isuzu/Trooper.htm   but I could do with more just so I can understand if everything is working ok.

I have a 1999 LWB trooper citation, 3.5 petrol auto. The shift on the fly is via a button on the dash.

The main question is about the front wheels hubs, drive shafts and what should be rotating and when.

Reason for asking the question.

I jacked up my nearside front corner to inspect the break pads and noticed that on spinning the wheel the drive shaft and front prop shaft also rotated, so I jacked up the other side and noticed the same thing.
I therefore looked at the full workshop manual (on CD) to see if this was meant to be. Unfortunately I’m none the wiser from reading it.
What I did notice is that vacuum solenoid valves are part of the setup, so I’m guessing that when the engine is running and the trooper is in 2WD the front hubs are somehow disengaged.

So if this is the case what should rotate when the engine is running and I spin a jacked up front wheel? Just the wheel , the wheel and drive shaft, the wheel driveshaft and front prop , or has something seized and when in 2wd whether the engine is on or off , only the wheels should spin ?

Its worth noting that I have not used the trooper in 4WD yet – I posted before http://www.itocuk.co.uk/forums/viewtopic.php?t=3605  about a problem I had getting into 4wd that may have been rectified when my local garage raised the whole vehicle of the ground and I got the vehicle into and out of 4wd with no problem (following a loud clunk on the first try).
However as the weather has been good I’ve not had the chance to try 4wd on some muddy tracks so have not tested if the 4wd is working when vehicle is on the road.

Could there be a problem with the vacuum side of the set up? or is all working as it should ?

Some expert guidance would be greatly appreciated

Many thanks

Ian
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1999 Trooper 3.5 petrol auto citation.

[Google]

[ianh]

Just been looking through the site and I spotted this from eithan H on another subject but post also covers Shift on the Fly

http://www.itocuk.co.uk/forums/viewtopic.php?t=2813

He explains how the shift on the fly system works via the Vacuum Solenoid Valves (VSV's)

I will jack up the car and start the engine. I'm expecting the left half shaft to rotate when I spin the left (nearside) wheel but the front prop to stay still. Is that correct?

Not sure what to expect when I spin the right (offside) wheel.

Again any assistance most welcome
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1999 Trooper 3.5 petrol auto citation.

[markymoan]

I honestly dont know a thing about shift on the fly, but ive no doubt someone does,
Maybe i should post some nonsense and hope someone corrects me  
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[eithan h]

ian as far as i remember you are correct, the near side half shaft is split where the solenoid valves are so spinning that wheel should only turn the small driveshaft you can see going in to the axle. when you turn the off side one though it will spin but so should the prop i think from memory, if you spin the near side wheel and the offside turns then that usually means the front axle is locked in position but not at the gearbox yet. some mechanics do this when they get a problem with the 4wd system and don't know how to fix it.
when you press the button it makes the motor move in the gearbox putting it in to 4wd which flicks a switch in the side of the box activating the solenoids to pull a synchro across to lock the front axle in 4wd.

[SAMLUDVIG]

the system works on vacum from the engine and on the fact that the long half shaft is split
when the engine is shut the is no vacum and thus the half shaft two parts are engaged so if u turn that half shaft you basicly turn the front drive shaft (as long as the other half shaft is stoped -otherwise the motion will otake place only in the diff case)
but when you turn the engine on it creates vacum that controls the engagment of the halfshaft

in order to be able to shift on the fly a basic principal has to take place and that is the speed of the front axle/driveshaft has to be equal to that of the rear otherwise speed difference occuers between two parts of the transfer case that supose to engage together

when u dont want 4x4 u disconect one halfshaft and that way only one halfshaft mooves the gears of the diff case (planets and side gears)to one direction and causes the other halfshaft to rotate counterclock wise
in this state the ring/pinion doesnt rotate at all and doesntthe front drive shaft which meens a speed difference in the t.case which meens noshift on the fly - kapish ?  

[eithan h]

thats sort of correct just out on a few things!