Questions: What is the Patrol drivetrain configuration?

[Des Curly]

Hello,

I have a query: What is the Patrol (specifically GU's) drivetrain configuration? I understand how fully-manual hubs on traditional part-time 4x4s work (in the context of front and rear diffs but no centre diff and a transfer case that can be put in either 2- or 4-WD), and I understand how "always-locked" hubs on more modern full-time 4x4s work (in the context of having front, rear and centre diffs, with the centre typically (always?) being lockable and no switching from 2- to 4-WD). What's the setup in the Patrol?

I assume it's a case of front and rear diffs, no centre diff, 2- or 4-WD switchable transfer case and front hubs that are either locked or free. Following on from this how do the so-called "auto" hubs in a Patrol (specifically GU's) work?

The best I could find is this, which isn't terribly conclusive: http://www.4wdaction.com.au/forum/showthread.php?t=32121

Thanks in advance.
Des

[YNOT]

I assume it's a case of front and rear diffs, no centre diff, 2- or 4-WD switchable transfer case and front hubs that are either locked or free. Following on from this how do the so-called "auto" hubs in a Patrol (specifically GU's) work?

Thanks in advance.
Des

You understanding is correct. Part time 4WD (selectable 2 or 4WD) with lockable hubs (manual or auto depending on model and specification), no centre diff.

Auto hubs are the same GQ and GU, they are an auto hub (much the same as any other auto hub) except that they have a manual over ride that allows you to manually lock them in using the wheel brace. This set up, although not as strong as the full manual hubs, give you the best of both worlds. An auto hub for those times when you're not expecting to need 4WD, and a manual hub for when things get serious. Some owners never bother to manually lock them in as they find the auto lock does everything they need, but they run the risk of the hub unlocking when you change direction. Manually locking them stops them unlocking.

Tony

[Des Curly]

Thanks for the confirmation.

I'm very curious to know how the auto hubs work. In particular, under what conditions do they lock and unlock. It sounds like it's torque related: putting the transfer case into 4WD delivers torque to the front axle which the front hubs then "sense", causing some internal mechanism to effectively bind and therefore lock the hub. This seems like it would be consistent with unwanted unlocking under direction change: when changing from forwards to backwards (or vice versa) there's a moment where the applied drive torque would be zero (how long this lasts would be dependent on the internal backlash I expect) which would cause the hub to "think" it's back in 2WD and therefore unlock the hub. Does this sound right?

[YNOT]

Correct.

Tony