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The other day my '03 Ford Fiesta suddenly failed in 4th gear when I changed from 3rd to 4th. My revs shot right up reaching roughly 5000 without any acceleration then after a few seconds the revs went back down to normal and speed eventually went faster but it's happening all the time. 1st and 2nd work fine, but 3rd and above fail in speed and revs shoot right up all over. 3rd gear was not actually that bad at some points. This started as I just came off a slip road onto a motorway so it was a bit scary as my car struggled to reach speed but eventually it got to 70mph.

I left my vehicle at a garage as soon as I got to my home town.

Does anybody know the cause? I'm waiting for my local garage get back to me as well.

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1 Answer

Most likely cause is a worn or misadjusted clutch. The clutch disc is slipping meaning that all the engines power is not being transmitted to the transmission. Cost of a clutch replacement is to varied to give an accurate estimate.

Clarification

Note

  • Energy will always take the path of least resistance.
  • From a clutch's perspective, it is much more stressfull to turn the drive wheels faster when the vehicle is in motion compaired to when accelerating from a full stop.

When accelerating from full stop - If the energy being transfered is too great the first to lose traction will be the tires. If the clutch was worn enough then once the tires had gained enough traction to overpower the clutch's grip, this is when the slippage would occur.

When accelerating form higher speeds (50mph @ ~1500rpm) - The weakest link now becomes the clutch itself since it is rather difficult to spin the tires at this speed (for normal cars). The friction/heat generated between the clutch assembly and flywheel is much higher and in turn the clutch loses it's traction and RPMs go up but the vehicle does not accelerate. A new clutch, which would be much thicker, will be able to distribute this heat much more effectivly and in turn keeping it engaged.

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You beat me to it. I agree 100%, for what it's worth. –  cinelli Jun 23 '13 at 3:48
    
Why would the low gears work fine if it's the clutch? –  R.. Jun 23 '13 at 4:24
1  
It is much more difficult for a clutch to grab or hold at higher speeds then when comming off a stop. The clutch is hotter at the higher RPMs and the strain on the clutch is much greater. –  cinelli Jun 23 '13 at 4:49
    
what would happen if u kept driving for a few days? –  user3509 Aug 4 '13 at 19:49
    
At some point the clutch will be badly destroyed enough that the car won't move at all under it's own power. Well before that point there will be sufficient damage done to the flywheel that it will require replacement (instead of a simple resurfacing). You don't want that to happen. On my cars for example, the flywheel part itself costs twice what the rest of the clutch job (parts and labor) does! –  Brian Knoblauch Aug 5 '13 at 11:33
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