Fo­cus on tech

Leisure Wheels (South Africa) - - CONTENTS -

Geared down for bet­ter per­for­mance

Some mod­ern 4×4s are too clever. With state-of-the-art au­to­matic gear­box tech­nol­ogy, the mak­ers of th­ese 4×4s claim there is no longer a need for a trans­fer case; with an ex­tra low first gear, th­ese ve­hi­cles can han­dle some off-road driv­ing. This month we fo­cus on trans­fer case tech­nol­ogy. And if the so-called kort stokkie re­ally has be­come re­dun­dant and ir­rel­e­vant.

There we were, on a moun­tain in Le­sotho. It was 11pm and we were ut­terly lost. We were driv­ing a shiny new Volk­swa­gen Amarok 2.0BiTDI 4Mo­tion AT and a Nis­san Pa­trol 3.0TDi.

We had taken a 60km track which sup­pos­edly led to Se­monkong, a road la­belled ‘bad road’ on a Le­sotho map. In the be­gin­ning, it was in­deed a bad road. Later, it evolved into a ‘very bad road’. As the hours ticked by, the go­ing got in­creas­ingly tricky, and the track turned into a grade four 4×4 ob­sta­cle course.

By then it was dark. We were on the side of a moun­tain on a track that made Sani Pass look like a four-lane na­tional high­way. It was not quite what we had in mind with the whole ‘bad road’ deal.

Still, we had no al­ter­na­tive other than to push on, re­gard­less. The Volk­swa­gen was fit­ted with the ZF eight-speed au­to­matic gear­box that, around town and on the open road, had proved ab­so­lutely bril­liant. But this moun­tain... this was some­thing quite un­like what the VW en­gi­neers in Ger­many had in mind when they said this gear­box, with its lower-than-nor­mal first gear, was a handy re­place­ment for the tra­di­tional trans­fer case, as used in a pukka 4×4.

Take the Nis­san Pa­trol, for in­stance. It has a trans­fer case, con­nected to a tra­di­tional kort stokkie, or short(er) sec­ond gear lever, in the cabin. For nor­mal driv­ing you leave the part-time 4WD sys­tem in 2H, with only the rear wheels pro­vid­ing propul­sion. For gravel roads and slip­pery driv­ing con­di­tions, you can se­lect 4H, and the drive is split 50/50 be­tween the front and rear axles.

And for the re­ally, re­ally tough 4×4 bits, where speed is not im­por­tant but low-down grunt is, you se­lect 4Low, for five low-range ra­tios and a top speed of around 60km/h. The rest of the Nis­san was equally old school: there was the lad­der-frame chas­sis, the ex­cel­lent wheel ar­tic­u­la­tion and a com­plete lack of elec­tronic driv­ing aids.

The Nis­san and VW rep­re­sented the two dif­fer­ent ends of the 4×4 driv­ing

spec­trum. One is all old­school driv­ing skill, the sec­ond is a tech­no­log­i­cal piece of equip­ment with fancy trac­tion con­trol and the low first gear which is sup­posed to pro­vide for­ward mo­men­tum.

Driv­ing the two cars on that dan­ger­ous track proved to be a wa­ter­shed mo­ment. The Nis­san was re­ally tricky, re­quir­ing just the right gear, the right mo­men­tum, pre­cise throt­tle in­puts and del­i­cate steer­ing in­puts.

The VW was com­pletely dif­fer­ent. Point it in the right di­rec­tion, add throt­tle – and keep the throt­tle at a con­stant in­put point – and the trac­tion con­trol sorts it all out, al­most mirac­u­lously main­tain­ing for­ward mo­men­tum.

The VW proved much eas­ier to drive on that type of ex­treme ter­rain than the Nis­san. The short first ra­tio in the au­to­matic gear­box cer­tainly did its job on that moun­tain.

But here’s the thing: if we had to drive a moun­tain track like this on a daily ba­sis, we’d opt for the Nis­san, ev­ery time, ev­ery day. Even though the VW may flat­ter the driver with its elec­tron­ics – and it may last a few years do­ing it, too – it was never in­tended as a hard­core 4×4 re­place­ment. In­stead, it’s aimed more at aid­ing the oc­ca­sional bundu basher.

The Nis­san’s driv­e­train, on the other hand, was de­signed for this type of driv­ing from day one, and it will take this kind of beat­ing day in and day out.

What is it about a trans­fer case that makes it the bet­ter op­tion for hard­core 4×4 driv­ing then?

Shift­ing the fo­cus

A trans­fer case is con­nected to the ve­hi­cle’s gear­box and re­ceives its drive from the gear­box, too. This power trans­fer be­tween the gear­box and the trans­fer case can be done through gears, hy­draulics or a chain drive.

The driver can, in most cases, se­lect be­tween 2H (rear-wheel drive only), 4H (four-wheel drive high range with the drive split 50/50 be­tween the front and rear axles) and 4Low (four-wheel drive low range with the drive split 50/50 be­tween the front and rear axles).

Essen­tially though, the trans­fer case re­duces the gear­box ra­tios to in­crease low-speed torque, to en­able the 4×4 to crawl over rough ter­rain at the slow­est pos­si­ble speed with the most torque at the driver’s dis­posal. Th­ese ra­tios vary from 4×4 to 4×4.

For in­stance, a Jeep Wran­gler Ru­bi­con’s trans­fer case ra­tios are lower than those of the Jeep Wran­gler Sa­hara. The Ru­bi­con can crawl at an even lower speed than the al­ready very ca­pa­ble Sa­hara over those large boul­ders, of­fer­ing bet­ter con­trol and more pre­ci­sion, and less chance of ex­pen­sive dam­age.

Then you also get cases like older gen­er­a­tion Subaru Foresters: the non-tur­bocharged ver­sions were fit­ted with what Subaru called re­duc­tion gears. This trans­fer case was not de­signed for hard­core 4×4 driv­ing but rather for drag­ging a car­a­van out of a muddy camp­site.

Op­po­site page, top: The Jeep Wran­gler Ru­bi­con’s trans­fer case ra­tios are lower than those of the Sa­hara model, en­abling it to crawl along at lower speeds. Op­po­site page, left: The gear lever in a VW Amarok au­to­matic. No trans­fer case here but rather a shorter first gear and an off-road mode with all sorts of elec­tronic trick­ery. Top: The Nis­san Pa­trol rep­re­sents ev­ery­thing we love about old school driv­ing, as it re­lies on driver know-how rather than elec­tron­ics. Above: The tra­di­tional lay­out of a 4×4: main gear lever in the mid­dle and the fa­mous kort stokkie next to it. Some peo­ple reckon it’s a thing of the past but in­ter­est­ingly, Suzuki binned its push-but­ton sys­tem to re­turn to this ar­range­ment on the 2018 Jimny.

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