Just a little levity

[Tim Payne]

A distant relation, who had been driving his SWB SII for quite a while, asked me to show him how to get through a stream and boggy patch in a hilly part of Devon. I engaged 4WD, drove down the bank, through the boggy bit, and he drove back. Whilst driving I could feel the Landy fighting with itself, something wasn't right ... He drove, I went to open the gate, and saw the rear wheel turning, and then spinning backwards on the uphill side, on the grass. I suspected .... Put her in 2WD, drove onto a fairly steep, dry, tarmac hill, braked to a stop, popped the yellow, gently eased off the brake ... and went nowhere.  I asked him if he had had any diff work done, and sure enough the front diff had been changed (quite a while ago !!) and was a higher ratio than the back. I suggested that the taller gearing was an improvement, that the rear diff would be easier to change, and that he should go and have a little chat with the garage that did the front diff work .... All came out fine in the end. Talk about "wind-up" :)

[landie57]

Not the first time that has been done. My sons were competing in the Baskerville Challenge when the youngest broke a diff in his series one during the time trial. Luckily lunch break was called, so they rushed back to the campsite and quickly changed the diff using the spare they had. It was only when driving back to site to complete time trial they realised something was not right. It didn't cause too much of a problem and they went on to win, again.

[TDC]

I once read or heard that, on a 4WD, a slight difference between the speed of rotation of the front and back wheels added some extra "torque", "tension" or "wind up" (no accurate description available) that added to and assisted  traction on soft ground. 

I've never investigated if there is any basis in physics for this. It could be rubbish! It could, however, have actually helped young Moore to the win.

If it doesn't assist, does it hinder or do nothing - there must be some effect?

Perhaps some of the viscous centre diffs, power apportioning drive units or even traction control electronics on later vehicles achieve some of this effect either by design or coincidence.

[mutley1954]

 Having matching wheels and tyres is also very important for permanant 4x4, ask any Freelander 1 owner, as a difference will soon
goose the centre coupling.  At least with a relativley simple part time set up you can get rid of the unwanted torque easily, when I drove
4x4 MK military Bedford trucks years ago, fitted with big bar grip sand tyres it was common to feel the wind up thru the steering, but easy to unwind it all by reversing , once back on tarmac .     The modern SUVs are often not as forgiving, just displaying an orange warning lamp
on the dash.

[albion1938]

Back in the '70s one of the customers at the parts place where I worked on London ran around all the time in an 80 on 600 front tyres and 750 rears. I suppose it worked OK because of the freewheel but would probably been a bit odd when locked.
Bernard

[Tim Payne]

Probably as in line with every other Free Wheel 80 owner, I used to always fit a pair of new tyres on the back, and the part worns on the front. It would still kick up gravel in reverse though.