Outer Limits 4x4 Board

No-one has been able to give me a definitive answer.

My '84 MQ SWB (or most 4WD I guess):
What (if any) is the problem with using it in 4H on asphalt.

It might sound like an obvious question, but as I am new to 4WD - I have found no-one who has answered it! "They" have told me you should NEVER drive your vehicle in 4H (or 4L) on anything but dirt or sand... something to do with wrecking the gearbox/transfer irriparibly...

Can you drive on asphalt in 4WD (ie. 4H) for any great distance - or are "they" right and it should NEVER be done?

Also, can someone explain to me the shifting method... my handbook for this '84 patrol seems to be misplaced in the from one of the 20 people that have owned it before me! (imagine THAT!??!)

I believe it is:
2H - obvious.... normal...
2H with hubs locked - drives the diff and shaft with no extra benifit - but "they" say you shouldn't do it for too long... its good for getting rid of all the crap builtup on the shaft etc.. but not much else(??)
2H - 4H... differing opinions: some say "come to a complete standstill - change it, then lock the diffs" - others say "you can change @ <25kmh ie. whilst moving) - lock the diffs either before or after... who's right?
4H - 2H ... again differing opinions... some say "at stand" still others say can do < 25Kmh
4H-4L - complete standstill

I just can't work out: I am bashing through the bush, then come along an asphalt road... do stop - change from 4H to 2H, then when I get back onto the dirt 2H-4H??

Driving in 4wd on a tarmac road will wind your transfer case up because the tyres won't have any slip in them and the road.

This is because the front wheels can turn at a different rate then the rears (steering).

It's similar to what happens when you have a rear locked diff and driving it on the road, they will chirp around corners on tarmac because the inside wheel is turning at a slower rate.

I don't think it's a big deal if you are driving straight (all four wheels should turn at the same rate), but for the sake of 3 seconds changing out of 4wd it's not worth finding out what happens.

Basically if you do it and wind the thing up tight, whatever is the weakest part in your driveline will break.

Dont do it. Mq's have a habit of staying locked after you release lever on hard surfaces due to wind up , however minute, and WILL wreck front diff ot transfer. It only takes a few mm in tyre overall diamater to give a few metres of pressure after a couple hundred yards.

If you have to do it or forget one day, drive in reverse and wind wheel from side to side, then forward again. If you are still not sure jack up one front wheel and it will release tension.
Manual front hubs will also aid BUT they have been known to hold in with wind up pressure too

Bazzle

Dont do it. Mq's have a habit of staying locked

I haven't as yet... played the "better to be safe" game...

but it is interesting to note.. I haven't found it written ANYWHERE... (I have scoured google all day today)

Thanks for your comments! I can now rest better knowing that I have been doing the right thing! Prolly a good excuse fo a long drive to hop out and strech the 'ol legs before locking hubs and kicking dust..

Thanks.

this might sound like a stupid question, but what is "wind up".

mickyd555 wrote:this might sound like a stupid question, but what is "wind up".

Hold a flat steel ruler by a hand at each end. Twist... tension is held in ruler. Substitute ruler for across an axle or from front to rear thru xfrer by one wheel or end turning a different arc, (turning, tyre size diff etc)

Bazzle

'Wind up' is the result when both diffs are locked by the transfer case and the different axles etc spin at a different rate. There is no 'give' or slipping in the transfer case and hence wind up. This happens when the front and rear diffs travel different distances and this can result when tyres spin, the diametre of tyres are different and heaps of other reasons. It is similiar to a diff where the centre will 'slip' to allow for the different distances each wheel travels for example when turning a corner. In a normal 4x4 the transfer case allows no 'slip' and any difference in the distances traveelled front and rear will develop as wind up and can result in breakages. some 4x4's which are constant 4wd distribute power to front and rear on road through a centre 'diff' and when offroad that is why that centre diff must be locked to engage the effect of a normal transfer case..... hopefully this makes sense if not i'm sure others may explain it clearer.

also when you go around corners the front wheels travel further than the rear wheels, even if you have open diffs front and rear it'll still wind up bad if its (Transfer case) locked on a high traction surface i.e. hubs in stick in 4H or 4L.
If you are driving with the hubs locked in and in 2H you can just slot the stick to 4H provided wheels aren't spinning and youre going fairly straight.

If the hubs aren't in and you try to put the stick in 4H from 2H it'll grind as the front shaft comes upto speed (bad) as the hubs are out and not turning the front shaft/axles.

personally when i get to hard stuff i put the hubs in and keep driving in 2H until i need 4H it can be engaged or disengaged at pretty much any speed if the car is straight and tyres are the same diameter all round - and hubs in
4L come to a complete stop to engage or disengage...