Author Topic: Not sure if Diff lock is working? Disengaged  (Read 301 times)

Offline MCMOND

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Not sure if Diff lock is working? Disengaged
« on: September 03, 2018, 12:41:18 PM »
Iíve read that if you jack both wheels up with the diff lock knob in( diff not locked) then when you turn one wheel the other should turn opposite direction. Mine does this, however Iíve also read that if you simply jack one wheel up with diff lock knob in (diff not locked) you should be able to turn the wheel with it in gear? I cannot do this unless I put the vehicle in neutral. Could someone help explain this to me. Iím concerned that the vehicle diff is stuck in locked position. The dash lights do not work for the diff lock however that is probably because the wires to the switch on the transfer case arenít connected. If the diff lock were stuck in the locked position would I experience anything different with steering etc.

Offline 303Gunner

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Re: Not sure if Diff lock is working? Disengaged
« Reply #1 on: September 03, 2018, 01:13:24 PM »
The Perentie is a "Constant 4x4" with a differential within the transfer case to allow different speeds of the front and rear driveshafts when travelling on hard surfaces. The diff lock knob DOES NOT lock either of the axle differentials, it only locks the centre diff within the transfer case. Both axle differentials are what's known as "Open" diffs with no locking.

When the two wheels of one axle are raised off the ground, turning one wheel will cause the other to rotate the opposite way due to the differential spider gears. The driveshaft will not rotate, as it is connected through the centre differential (regardless of it being locked or unlocked) to the other driveshaft, which is connected to the other two wheels still on the ground.

When you only raise one wheel, obviously you can't rotate the opposite wheel still on the ground (well, you could if your hands could make enough torque to make the vehicle move!). The only other moving part you could cause to turn is the driveshaft. As stated above, this is connected to the other axle driveshaft through the centre differential (either locked or unlocked), and as those wheels are also on the ground, you won't turn it. However, drive within the transfer case is also connected to the gearbox via the input shaft. The transfer case differential is also unable to turn the input shaft as when the gearbox is in gear. Putting the gearbox in neutral allows the centre diff to turn the input shaft as you have noted.

To test if your centre diff lock is working, raise one wheel with the gearbox in neutral and the diff lock knob IN. The wheel should turn. Now engage the diff lock by pulling the knob OUT (note you will need to have the engine running as the engagement is operated by vacuum). When the centre diff locks, you should not be able to turn the one wheel in the air. You might be able to turn it as much as a quarter rotation to allow the diff lock dogs to engage, but after that only an inch or so of backlash.

The constant 4x4 system is really only a "One wheel drive". If you lose traction on ANY ONE WHEEL, the all the engine torque will go to that wheel and spin. Locking the centre diff, means you have to have two wheels spinning to lose traction. Fitting axle differential locks means you will have to have all four wheels spinning to lose traction.

Offline tona

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Re: Not sure if Diff lock is working? Disengaged
« Reply #2 on: September 03, 2018, 03:23:48 PM »
 ;)    WELL explained gunner, we need more of you guys here ,TONA.

Offline RAF101

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Re: Not sure if Diff lock is working? Disengaged
« Reply #3 on: September 03, 2018, 09:53:37 PM »
And with 6x6?

Offline 303Gunner

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Re: Not sure if Diff lock is working? Disengaged
« Reply #4 on: September 03, 2018, 11:02:21 PM »
Same. The rear axle engagement is also operated at the same time by the same switch, but uses a separate vacuum circuit to engage the rear output, and a separate contact switch to activate the "tell-tale" light on the dash. It is therefore possible for one or the other to fail individually. It is also possible to modify the system with two switch units to engage the centre diff lock or the rear drive output independently. The dash lights that illuminate when the CDL or rear output are engaged are on separate circuits with individual switches on the transfer case, and illuminate when the respective dog gears engage.

To check if the 6x6 rear axle engagement is working when the CDL knob is engaged, jack up one of the rear wheels. It should turn. With the engine running, pull out the CDL knob. The jacked up wheel should now not turn. This is regardless of what gear the gearbox or transfer case is in, as the rear output locks the rear driveshaft to the middle driveshaft output.

Offline MCMOND

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Re: Not sure if Diff lock is working? Disengaged
« Reply #5 on: September 04, 2018, 02:31:31 AM »
Thanks Gunner
Mine works as advertised just need to get the wires hooked up so light will work. When Iím under the vehicle I see one wire (black) that looks as though it attaches to the switch however I donít see a second wire. Possibly just a ground wire that can be attached to the case or is something missing. Again thanks for the clear explanation.

Offline BEARMAN

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Re: Not sure if Diff lock is working? Disengaged
« Reply #6 on: September 04, 2018, 08:21:20 AM »
Yeah, 2nd wire is usually just a short one to earth from the other terminal.
09/1998 Perentie 6X6 ARN202516 - BRUTUS

Offline MCMOND

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Re: Not sure if Diff lock is working? Disengaged
« Reply #7 on: September 12, 2018, 04:09:25 AM »
Thanks for all the good help.