Isuzu D-Max Gearbox & Transmission Problems

Isuzu lifted the warranty on its vehicles to six years/150,000km for all utes sold after May 1, 2019. Unfortunately, it sounds like your car was on the road in 2018, which means it was covered by a five-year/130,000km warranty. Although you haven’t yet covered 130,000km, the vehicle is more than those five years old so, technically, the problem is not covered by warranty.

However, I think it would be worthwhile contacting Isuzu Australia’s customer service division and pointing out the car’s service history and its mileage. Isuzu may then decide to help with the cost of repairs on a pro-rata basis given the circumstances. It is not obliged to, of course, but it’s definitely worth asking.

Sandy conditions are incredibly hard on every aspect of a four-wheel-drive. The sand itself constantly shifts under the tyres and clings to them as well, dragging them down and making the engine and transmission work very hard to maintain progress. You may have already noticed that you use a lot more fuel in sandy country and it’s all because you need to be constantly making more power to maintain speed than in normal conditions. Turbocharged engines and automatic transmissions, in particular, can get very hot very quickly in sand.

With that in mind, it’s very possible that something in the driveline got hot enough for the car’s computer to go into limp home mode to protect what ever was hot from damage. Limp home mode often involves limiting engine revs and turbo boost, both of which contribute to heat production. This would explain why the car would not climb a crest but came good after a break.

Problems like these are hard to diagnose remotely, as there's a lot going on in a modern gearbox. But, conventional wisdom suggests that a noise followed by a series of failures of the same component (the oil seal) means something inside is bent or damaged.

The noise is potentially being caused by something misaligned and rubbing or a damaged bearing, and the blown oil seal is the eventual result of the damage/swarf/heat/friction that results. The other possibility is that the rear gearbox seal is being destroyed from the other end of things, as in the tailshaft. A bent tailshaft could set up harmonics, friction or vibrations that could kill the seal, but you'd imagine there'd be a vibration through the whole vehicle at speed if this was the case.

Your vehicle is under warranty (six years of it from new) so make sure the dealer is aware of the problem and their obligation to fix it.

The first thought here is that you’re dealing with a dodgy throttle-position sensor or some other sensor that is giving the on-board computer a reason not to exceed 2500rpm. Or tricking the computer into thinking that the engine is spinning faster than it really is. Have you had the vehicle scanned? It’s a cheap way of reducing a lot of the guesswork in a case like this.

Like any engine, of course, a turbo-diesel won’t rev beyond the speed that the fuel supply can support. You say you’ve changed the fuel filter, but have you checked the pump pressure and the fuel-delivery rate? A problem with the pump or fuel lines could easily produce the symptoms you have. You could even have a blocked fuel pick-up in the tank.

The other problem with modern turbo-diesels is that they are prone to clogging their intake systems with a black gunk that is a by-product of soot and oil mist from the vehicle’s exhaust-gas recirculation and crankcase-ventilation systems respectively. This black, ooze can sometimes almost completely block the intake path for air entering the engine and will cause all sorts of dramas, including the one you’re seeing.

It’s clearly frustrating you, but I don’t believe you’ve copped a lemon on the basis of what’s happened. Isuzu fixed the diff, end of story, they also replaced the first pump under warranty, again end of story. The issue is why have two pumps failed, and why didn’t Isuzu cover the second pump. These are questions I would be putting to Isuzu. I’m guessing that the second pump wasn’t covered because the warranty had expired after three years.

Isuzu spokesman Dave Harding replies: Isuzu Ute Australia values all customer feedback. Our service team has confirmed with Mr Cooke his vehicle is not defective and that the phenomenon he was experiencing is in fact a characteristic and in no way detrimental to the safe operation of his motor vehicle".