The best transmission is…

A guide to what’s underneath the next 4WD

NZ4WD gets to drive some exceptional vehicles each year. Often, talk turns to favourites among the test drives. Almost as often, talk is also about the mechanicals: engine, transmission, 4WD system.

Some readers – a very few – may have had the ‘pleasure’ of driving trucks like the early Nissan Patrol with its threespeed floor shift manual-everything driveline. Or the notchy four speed of a Series 2 Land Rover.

It’s remarkable that manual transmissions were once the only choice in 4WD shifters, and today they are almost extinct.

‘Best of breed’ is open to debate, but one of the good ones was the turbodiesel/five speed/full time 4WD used in the Defender 90 County. That wee truck didn’t need fancy electronic hill descent control, in low ratio first gear it would crawl down incredibly steep slopes with the driver’s feet inactive on the cab floor.

Fast forward 25 years or so and it’s auto-everything, electronic control of transfer case and transmission, and eight or even ten-speed automatics.

A few aspects of set-up will keep these modern and costly automatics out of gearbox workshops. First, abandon the stock fluid cooler and fit a big aftermarket one between radiator and grille. Autos die fast if their fluids get cooked. Second, even if the trans is

“filled for life”, monitor the fluid regularly. If it starts to smell burned, that means it has lost its effectiveness and needs replacing. New fluid can cost $100 or more, but that’s cheap compared to a replacement trans at $10,000 or more.

Last, all auto transmissions have breathers. Buy some suitable hose and run the breather up to at least dash level. That means water is much less likely to go where it shouldn’t when offroading.

Least suitable, if the 4WD is going to be used in gnarly conditions or will tow heavy loads a lot, would be CVT. The technology behind belt drive transmissions is attractive to auto brands building crossovers and ‘soft roaders’, but not so handy for hard work. Heat buildup shortens the life of the drive belts and unlike a ‘proper’ auto this isn’t something that can be addressed by a cooler radiator. When CVTs are used in motorsport (mainly in UTV racing) they are often fitted with blower units that direct cool air onto the belts, but in road/ offroad applications this is not possible.

In the end, of course, the best transmission for the job is a personal choice, and it may well be the transmission in the truck parked in the driveway. It’s food for thought, though, when shopping for a new or pre-loved 4WD.