Rumbling grumbling sound under acceleration
Discussion
Coming home from Poole Thursday evening my L494 SDV6 developed an odd grumble along the A35.
63k miles, oil service 500 miles ago, all up to date with servicing, zero alarms on the diagnostic tool (I know right!) Last night up on a jack I checked each wheel for play in the hub bearings, all good, CV boots all good all round, no signs of any lubricant leaks under the car, exhaust given the once over. Car shifts smoothly, no bangs clangs or jumping of gears in auto and manual mode on the paddles or the stick, all off road modes selectable and engaged incl high and low ratios. No nasty burning smells coming from the car.
Symptoms are as follows.
In Drive at any road speed with light throttle pressure to maintain road speed the rumble/grumble is there, cruise at say 60 mph at 2k rpm engine speed foot off accelerator no grumbling, revs slowly fall away as road speed decreases no noises, slight touch on accelerator even adding 50 - 100 rpm of engine speed and the rumbling grumble re-appears.
Road speed 60 mph, 2k rpm transmission to neutral, grumbling stops as we coast, press on throttle, rpm climbs to 4k no grumbling sound, road speed around 50 mph.
Inside the car it sounds like the noise is coming from the rear of the car, but sound travels in a weird way under a car and it does sound like a blown exhaust but doesn't blow when in neutral at 3 or 4k rpm stationary.
So, I think I can rule out the following, front and rear differential, gearbox & torque converter, transfer case, wheel hubs and bearings, but I'm stumped as to where to go next, any clues from the above most welcome.
63k miles, oil service 500 miles ago, all up to date with servicing, zero alarms on the diagnostic tool (I know right!) Last night up on a jack I checked each wheel for play in the hub bearings, all good, CV boots all good all round, no signs of any lubricant leaks under the car, exhaust given the once over. Car shifts smoothly, no bangs clangs or jumping of gears in auto and manual mode on the paddles or the stick, all off road modes selectable and engaged incl high and low ratios. No nasty burning smells coming from the car.
Symptoms are as follows.
In Drive at any road speed with light throttle pressure to maintain road speed the rumble/grumble is there, cruise at say 60 mph at 2k rpm engine speed foot off accelerator no grumbling, revs slowly fall away as road speed decreases no noises, slight touch on accelerator even adding 50 - 100 rpm of engine speed and the rumbling grumble re-appears.
Road speed 60 mph, 2k rpm transmission to neutral, grumbling stops as we coast, press on throttle, rpm climbs to 4k no grumbling sound, road speed around 50 mph.
Inside the car it sounds like the noise is coming from the rear of the car, but sound travels in a weird way under a car and it does sound like a blown exhaust but doesn't blow when in neutral at 3 or 4k rpm stationary.
So, I think I can rule out the following, front and rear differential, gearbox & torque converter, transfer case, wheel hubs and bearings, but I'm stumped as to where to go next, any clues from the above most welcome.
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