lo - hi range shifting while moving with auto box?

[bedford4x4]

I've been looking through the workshop manual for the Isuzu 30/80 automatic and find that the transfer gearbox uses clutch packs like the main gearbox.

So now I'm wondering if shifting from low range to high range while on the move can be done without damaging anything. I used to put the main gearbox into neutral and then change the transfer ratios while the vehicle was moving, but with clutch packs in the transfer box, is it necessary?

I don't want to try it without asking others here first.

[Demonic]

Your talking about 'shift-on-the-fly', can do in a manual, dunno if i recoment it in an auto. in the manual you push the clutch in then shift into 4h or 4l then clutch out. cant really do that in an auto.

[geeves]

The book says no in both manual and auto. You might get away with it but it was never recommended here. I do change my manual from low to high while moving but over 10kph it makes noises so no faster

[Yarno]

I always changed my manual from hi to low at maybe 30km/h and low to hi when I would run out of gears at 60 ish, just push the clutch and shift, also would match a suitable gear for the speed. No idea about auto, maybe try bumping into neutral and give it a go, I will be when I get mine going, but mine will probable grind as the Nissan box doesn't have syncros.

[jezza]

I did it with my auto by accelerating slightly then letting the gas of then change gears, that way there is no load on the driveline

[bedford4x4]

Thanks guys. It is something that I'll have to try at very slow speeds and gradually increase the speed at which I change ratios to see if it works.

Personally I can't see why it won't work. If an auto gearbox's clutch packs are strong enough to cope with the engine output while in the process of changing gears, the transfer gearbox's clutch packs should be able to do the same job. As long as there is a clutch which engages or disengages between ratio changes, rather than just gears engaging or disengaging, it shouldn't do any harm.

And like Jezza, if you take your foot off the gas between changes, it should minimise the shock to the transmission.

BTW, double-declutching works for any manual transfer gearbox with a neutral. Don't the manual Isuzu transfer gearboxes have a neutral position?

[geeves]

in the manual box low 5th and high first are about the same so just changing low/high on its own isnt enough. You also need to select a different cog in the box