Noise when decelerating

[pjjoubert]

I have a 1998 Ford Explorer 4wd 4.0SOHC Automatic

The problem
1 When decelerating a noise starts that sounds like a hammerdril or chainsaw
the rev counter indicates revs just above normal idle speed but the noise
stays at the same pitch

2 If I apply the brakes the noise slows down until the car stops

3 This only happens on longer trips - over 20 miles

The current suggested solutions vary to much and cost from £300 - £2500

 

[Howard]

With the engine revs not changing that would point to something in the wheel or transmission area. You could try jacking it up so all the wheels are off the ground and spin them to determine where the noise is coming from. It might turn out to be something simple, had odd noises when stones get stuck in discs etc.

 

[janolsson]

I would be looking at the universal joints in the propshaft and checking the fluid in the transfer box as first point of call.
The uj could have too much free play which is quiet under drive but when spinning but not loaded allows it the rattle.
Same applies for the transfer box except this could be due to low fluid.