My Tacoma has been making a strange revving and rattling sound when the truck is in motion and the brake or the clutch is pressed and the gas pedal is released. I couldn't reproduce the effect when idling. I first thought it might be the heat shields around the exhaust assembly as it feels that's where the noise is coming from but they are all pretty firm. Doesn't feel like it's coming from the engine itself. The noise is sort of like as though something is stuck in the way of either the fan or the drive belt, which I inspected negatively. It does not happen every time.

Any pointers where to start looking?

  • If you coast in neutral does the sound occur? Does the sound occur when you have 4 wheel drive high engaged? – DucatiKiller Feb 9 '16 at 2:56
  • Not when coasting in neutral but I was able to reproduce the sound when in 4WD – amphibient Feb 9 '16 at 3:13
  • Have you checked the rear driveline u-joints? Actually all of them to include the drive axles up front. – Pᴀᴜʟsᴛᴇʀ2 Feb 9 '16 at 3:15
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    Does it make a lot of noise going over speed bumps or curbs? Could possibly be a worn bushing somewhere in the suspension or leafs in the rear. – Tobin S Feb 9 '16 at 6:45
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    That reminds me of a rattling sound I once had on a car, it turned out to be the starter pinion that wasn't returning all the way and was rattling against the flywheel teath occasionally. – HandyHowie Feb 9 '16 at 21:35

From HandyHowie's comment above, it could be the start pinion rattling against the flywheel under certain conditions (deceleration as you described). This interference could be cause by improperly placed starter mounting bolts/brackets, or bolts that were not fully torqued, allowing the starter to move. Drivelines have small tolerances of flexibility, which would be causing the noise during the deceleration condition, but obviously this was not intended from the factory, and nothing described would indicate problems with the driveline, so a loose starter is the likely culprit.

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