Why cars fail their MOT on driveshafts and CV joints
Driveshaft and CV joint faults fail 1.59 percent of car MOTs, almost all a split CV boot. Cheap if caught early, a full driveshaft if not.
MOT DATA · 4 min read
A small category dominated by one item
Driveshaft and CV joint faults fail 1.59 percent of car MOTs, and one single failure item drives almost all of it: a split or perished constant velocity (CV) joint boot, which alone accounts for 1.53 of that 1.59 percent. It sits well down the failure list, but it is one of the few faults that gets dramatically more expensive the longer it is ignored.
What fails
The boot is the rubber gaiter that keeps grease in and dirt and water out of the CV joint at each end of a driveshaft. Once it splits, the joint runs dry and picks up grit, and a joint built to outlast the car starts wearing out in weeks rather than years. The rest of the category is smaller: a worn driveshaft support bearing, a deteriorated flexible coupling, or loose or missing securing bolts.
What it costs
A CV boot kit is one of the cheapest parts on this whole site's list of failures, typically ten to twenty five pounds, and a competent garage can fit one in well under an hour if the joint underneath is still sound. Once the joint itself has run dry and started clicking or knocking on full lock, the job stops being a boot kit and becomes a full replacement driveshaft, commonly seventy to a hundred and fifty pounds a side in parts alone, more on four-wheel-drive cars with extra joints to cover.
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The salvage angle
Check for a split boot before almost anything else on the running gear, because it is one of the cheapest fixes here if caught early and one of the harder ones to spot from auction photos alone, since flung grease across the inside of an arch or a wheel is often the only visible clue. A knock or clonk on full lock on a test drive means the joint has already gone, so budget a full driveshaft rather than a boot kit. The Analyzer does not currently price CV joint work as its own line, so treat a heard clonk as a manual add before you bid.
Where to get the parts
Sourcing the part yourself rather than leaving it to a garage's mark-up is usually where the saving is. GSF Car Parts carries most of what a job like this needs, with click and collect from local branches.
Browse parts at GSF Car Parts →
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