4WD on LJ78 Prado

[AndyS]

Gents,

I've recently purchased a jap import landcruiser. I'm very impressed with the condition etc. However with the lack of a manual etc I'm a little lost with the 4wd. On the dash I've a couple of buttons, one for locking habs (self explanatory) and the 2nd marked H4 which engages the forward drive shaft from the main box ( powering the front diff). All appears very sensible except why would you ever want one without the other. Or is it that one can be disengaged at speed and the other can not? I must appear a prat to those battle hardened cruiser owners but before I wind the transmission up and burst the drive system what is it that I'm missing ??????

Andy :?:

[rob4wd]

hi
your h4 is for selecting 4wd.your locking hubs need to be engaged also.the sole reason for un locking hubs is to reduce wear and friction when normal road driving in 2wd.it stops the moving front wheels driving the front shafts and transfer gears needlessly.should give more mpg and easier steering.some people say even if you drive only in 2wd and unlocked hubs you should occassionally lock them to  run the shafts to keep things lubricated
regards rob swallow

[AndyS]

Hi Rob,

Thanks for the reply. Its not that I don't understand free wheeling hubs etc its more that I don't understand why there is a requirement for two switches. I can't imagine why you'd want H4 (4WD) without the hubs being locked or locked hubs without 4WD engaged. One switched either engaging or disengaging both systems together would make more sense to me,unless H4 can be engaged at higher speeds that the hubs.
I took the hubs apart and found the brushes as good as finished. Any idea where I'd pick up replacement brushes?

Cheers

Andy

[rob4wd]

i see what you mean and the only reason i can think of is the ability to use low ratio in 2wd if for instance you are on tarmac.you may find more info on wj's 4x4 and offroad homepage.as for hub parts i think the prado is similar to the 80 series.your dealer may help or try sor.com or man-a-fre. they will almost certainly have the parts but may not be familiar with the prado designation
good luck
regards rob swallow

[Sarah]

Hi,

You have a separate button for the hubs because you have electric hubs, us mortals with UK cars have manual hubs and have to get out to lock them. I guess it is easier for toyota to fit a separate button and keep the H4 swtich the same than it is to put it all into one... True you would not want H4 without hubs locked but to lock the hubs without 4WD is not so stupid, it allows the drive shafts and diff to be lubricated on road without wind up... I never unlock my manual hubs. You can engage/disengage H4 on the move up to 66mph (100kph), Likewise I guess the hubs, just don't do it in a bend or if you're already spinning wheels. Should the electric hubs fail the easiest option is to replace with manual hubs, common to Hilux, and Nissan and other vehicles, Aisin hubs are a Toyota company.

I guess the H4 is on a switch and low4 on the lever to make it easier to make 'flying' changes between 2 & 4WD without groping on the floor for the lever at 60mph, I used it all the time on the ice roads in Canada.

[AndyS]

Hi Rob, Sarah,

Thanks for the replies. That's me sorted with all the buttons and technical side of things, just to crawl underneath and underseal her now. Anyone takers???

Take care,


Andy