Changing fro 2H to 4H at speed - a lot of force needed?

[eehgil]

Recently bough a 2013 2,5 manual Hilux.

I feel that I need to use a lot of force on the transfer box lever when changing from 2H to 4H at speed. At stand still it is easy. Changing from 4H to 2H at speed is also easy.
Sometimes it helps to change 2H-4H-2H before taking of, then the next change in speed to 4H is easier - but not allways.

Yes, I am driving in a straight line when trying change from 2H to 4H.

The tyres are of same type and dimension. I have also recently changed all 4 wheels from summer- to winter-tyres, and this change dit not make any difference.

If it was a "transmission bind up issue" it also would be heavy to change from 4H to 2H?

I have tried different teqniqes, blipping the throttle, clutching, changing gearbox into neutral, turning the weel slightly side to side - but have not found that any of these make a difference.

Is it normal that there is a major difference in force needed on the transfer box lever at stand still versus at speed?

By the way: I love the fact that it is possible to change from 4L to 4H at speed, combined with the ADD disconect mod this make this drivetrain som practical and flexible

[Gipsy]

There is no synchro on the transfer case gears so they sometimes are difficult to change from 2h to 4h if moving too fast. At slower speeds it will be easier. Best is to stop for changing 2-4wd or at least take the revs down before changing. If auto, neutral is not needed but with manual, keep the clutch engaged.

[ptrl1600]

I think the issue here is that when changing from 2H to 4H while moving, the front drive shaft isn't turning in a vehicle with ADD, so it stands to reason that it could be difficult to engage. With a standard open front differential, the left hand side front wheel is driving the spider gears which constantly rotate without turning the crown wheel and front drive shaft. When shifting back to 2H, everything is turning, so disengaging is relatively easy as you're simply disconnecting the front drive shaft in the transfer.

I find it interesting that you say that you can change from 4L to 4H at speed? I almost have to stop to do that, but I have a front auto lokka fitted which keeps the front drive shaft rotating even when not in 4WD, similar to not having ADD.

[eehgil]

The non rotating front driveshaft is a logical explaination. So it is normal with cars with ADD that going from 2H to 4H at speed is heavy?

Is it easier in non-ADD cars? no differnce from stand-still vs at speed?

Yes, I can shift from 4L to 4H at speed, both with the ADD switch on and off. I have even changed at speeds up to 40km/h. then going from 5th in 4l to 3th in 4H. I do it like this:
-engange clutch
-gear lever to neutral
-transfer lever from 4L to 4H
-gear lever in gear
-clutch out.

However changing from 4H to 4L I have so far not been able to do in speed.

[NZMarkb]

You shouldn’t be changing from 4H to 4L at speed
At a crawl maybe

[Gipsy]

X2 what Mark said... Do Not shift the transfer case at speed, only at a crawl or stopped. Check the sequences as per the manual and the sticker in the vehicle(normally under the visor). If you want constant 4wd you should have bought a Prado or landcruiser.
This is how they are designed, with viscose clutch in the drive line.