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What is causing the automatic gearbox to clunk in my 2014 Mazda BT-50?

I have a 2014 model BT-50 auto 3.2-litre diesel. The car has done 130,000km and since about 90,000 it has developed an intermittent clunk in the first-to-second gear change. I have had the gearbox serviced twice and the mechanics couldn't find the fault. I have this week taken it to Mazda at Aspley to request an answer. It now clunks almost every change. The rest of the gear changes are smooth. They have diagnosed a faulty EGR valve and replaced it $1200 later. However, the gearbox still clunks. They charged me $165 for a diagnostic check and no solution. Any suggestions?

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.

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