Mazda BT-50 Gearbox & Transmission Problems

You shouldn’t be using Park as a brake, that’s not what it is intended for, and could damage the transmission. If you want to stop the vehicle change down through the ratios manually and apply the brakes. The problem is unlikely to be the wiring harness, it sounds like it’s deeper within the transmission. Have your dealer check it, or take it to an automatic transmission specialist.

You need to take it to a mechanic for a diagnostic check to find the cause of the problem. It sounds like it could be in the transmission; perhaps the powertrain module could be at fault.

Many owners have changed from a dual-mass flywheel when changing the clutch in their utes, and none have reported a major vibration problem after the change. I would doubt it is the flywheel that’s the problem, look elsewhere in the driveline.

I’d guess there’s some serious internal trouble and that you should take it to a transmission specialist to have it assessed.

There was a recall in November 2017 to fix a problem with a gearshift cable retaining clip that could cause the cable to come in contact and be damaged by the prop shaft. The result was that you couldn’t change gears and could lose drive.

It is a relatively common problem, and it’s made worse by towing in 5th gear.

I’ve had a flick through the BT-50 owner’s manual (and I suggest you do the same) and all I can find relating to a transmission warning light is a single 'powertrain warning lamp' which suggests something is not right somewhere along the length of the powertrain. Sometimes this light will come on in conjunction with the 'check-engine' light and it indicates that either a sensor has failed or there’s an actual problem with the hardware. Beyond that, the light doesn’t offer any suggestions on what might be wrong, but bear in mind that the four-wheel-drive system in this vehicle is electronically operated, so there’s lot of scope for errors.

A scan at a workshop should offer up some answers, but before you do that, just check that you haven’t bumped the rotary four-wheel-drive selector dial and have triggered the system into a mode it doesn’t like being in right now.

As there are no warning lights, and it recovers if left, it doesn’t seem likely that it’s an electronic issue, rather a mechanical one. It would worth checking the turbocharger.

This model Mazda BT-50 and its Ford Ranger counterpart (they’re the same vehicle under the skin) have had their share of automatic transmission problems over the years. There are known problems with the gears in the oil pump which are prone to wear, valve-body problems and a fault with the output shaft speed sensor which can also fail, forcing the gearbox back into first gear at relatively high speeds. All these problems could be contributing factors in the problems you’re seeing.

While EGR valves often need replacement (and I’m not disputing that yours did) I don’t imagine the EGR valve would have had anything to do with your gearbox problem. It’s not uncommon – nor unreasonable - for workshops to charge a diagnosis fee (it involves workshop time, after all) but servicing the transmission alone won’t fix it if it has any of the problems I’ve listed above.

I’d be checking the clutch to see if it could be worn out or close to.