1980 Nissan 280ZX Pricing and Specs

Actually, this is simply how a CVT operates. When you load the engine (and towing a caravan is a great way to do that) the transmission will switch to a lower ratio in order to keep the engine in its comfort zone and making enough power to keep everything moving at the speed at which you’ve set the cruise control. Because there are no set ratios in a CVT, this can sound a feel very alien when it happens. It's one of the things many people dislike about CVTs.

When you turn off the cruise control and allow the throttle to return to idle, the car detects that the crisis is over and changes the ratio to allow the engine to slow down as less power is needed. And that’s why it all feels like it’s returning to normal. But, really, what you’re hearing and feeling is just the CVT doing its thing.

You could be looking at something internally wrong with the transmission, but the clue that this might be something simpler is in the way the engine will start in Reverse which, of course, it shouldn’t (for safety reasons). The suspicion would be that the relationship between the selector (inside the cabin) and the actual gearbox is somehow out of synch. So when the selector is telling you the car is in Reverse, it’s actually in Park or Neutral, which is why the engine will start.

That might also explain why the car won’t select fourth gear; the position that actually coincides with Drive (or fourth gear) looks – from inside the cabin – to be the Neutral position. So, to check this, put the car in what looks like Neutral and, in a safe place, see if it moves when you give it some throttle.

Failing that, you’ve got two separate problems. The first is the inability to select fourth gear (which could be a hundred things) and a failure of the safety switch which is allowing the engine to start in Reverse.

This goes against everything we were told a generation ago about the transmission fluid in automatic gearboxes. In the old days, bits of clutch and metallic band would wear off the internal parts of the transmission, requiring the fluid to be changed to avoid this dross doing damage to the actual transmission.

The theory is that with today’s better transmission designs, materials and precision engineering, this is not going to happen and the vehicle can use the same transmission fluid for its entire operational life. Maybe it can, maybe it can’t, but I’m with you in being a bit confused about it all. My preferences (and that of many transmission specialists) is that even in a sealed-for-life transmissions, you won’t be doing any harm by replacing the fluid at sensible intervals. And if you do happen to flush out some rubbish in the process, the expense might be well worth it.

Bear in mind there are two types of fluid change. The cheapest is simply a case of emptying the transmission’s pan and adding enough new fluid to take the level back to where it should be. The second, more expensive, option is what’s called a flush. In this case, the fluid in the gearbox is changed, as well as all the fluid in the lines, coolers and other plumbing around the car.

The only catch with this would be if Nissan regards a fluid change as some kind of tampering and takes the view that this would void any factory warranty. So check with Nissan first. The correct type of fluid for your car’s CVT is also crucial.