Wierd rear booming noise

Hi guys, please help if you can. I drive a fab 2003 V8 autobiography with LPG, which Im really happy with.

Recently, I thought that I was getting some radio interference as the car has developed a quite loud random booming noise in the rear. As I usually drive with music, I thought at first that it was the speakers vibrating or the bass box had come loose in the rear. But the noise is not related to the hifi evident obviously by turning it off! The booming noise remains. It's almost as if there was a pimped escort driving behind me with a loud boom box in the back. It tends to kick in about 30-40mph, and I guess becomes slightly more noticeable at higher speeds, although not considerably noiser, just easier to hear. It comes and goes almost like the bass in music. It doesnt happen on bends, or on acceleration or deceleration....just as Im driving.

It sounds as if the bass speakers are on full but with all other sound been turned off, or a little bit like the buffeting noise you may get on a really windy day, driving at high speed.

I've had a landy man look at it, as I am off on a long trip next month but he had no idea, He took it for a drive with a mechanic who sat in the back and they knew what I was talking about but not the problem. He said wait for it to get worse and we can see then. It is definitely outside the car, and NOT inside and only when the RR is driven at reasonable speed. I also feel as if it is more easy to notice when the car is warm but this may be irrelevant.

Please offer whatever thoughts you like, as I could do with help please.

Do you have a rack on your roof? Mine gets a weird harmonic going at certain speeds and in strong winds.

no roof rack, but that is a good call. Its not however, quite as noisy as roof rack noise can be. It sounds as if it is coming from the rear, underneath nearer the nearside rear wheel.

what about a loose tailgate seal, letting turbulence in. Could also be the sunroof (if you have one)

its not the sunroof thanks, the noise def feels like the rear, but low down. I will have a look at the seal, but not sure what I'd look for.

It seems ok at first sight.

UJ? Wheel bearing??

When the torque converter lock-up clutch starts to wear on the ZF 5HP24 transmission it allows torsional vibrations through the driveline (there’s no TV damper on the LUC in the ZF 5-speed ‘box) and it’s most obvious when you’re travelling at about 30mph on a slight incline on light throttle in 4th gear (around 1300rpm). It sounds like you’re driving over a series of (quiet) cattle grids. Does this sound like your problem?

You can confirm it by closely watching the rev counter while it’s making the noise as the needle will be bouncing around by a couple of hundred rpm or so in sympathy with the noise. Also, if you move the gear lever into manual mode the noise will disappear as the LUC is disengaged.

The LUC only operates in this continuous slip mode between around 25mph and 56mph at light throttle openings. Below 25mph it's off completely and above 56mph it's locked solid.

Thanks Bemble for your indepth reply. I didnt get much chance to go on a long drive over the weekend, so its still not conclusive. The RR does need to warm up first, hence it takes a little while before it becomes noticeable. I think I could see the revs moving, but it was extremely difficult to maintain steady pedal control as the fine weather brought out sunday drivers. Im sure that the problem was still there after I had switched to manual, but Im going to try that again as soon as I can for a definitive answer.
finally, I am not sure that the noise goes away at motorway speed, so I need to check that out too. If I had to put money on it, I'd say that it was slightly more noticeable at 60-80 but not proportionately so. ie it isnt twice as loud at 80 as it was at 40.
Thanks again and I will revert back after switching to manual.

Datatek thanks. The Landrover specialist found no fault on his laptop so whatever it is, wasnt showing as a fault.

Typical. I go for a long drive and it doesnt seem to want to do it now. I will be back once it returns. I could sense the noise slightly, but not enough to warrant switching to manual....

Bemble said:

When the torque converter lock-up clutch starts to wear on the ZF 5HP24 transmission it allows torsional vibrations through the driveline (there’s no TV damper on the LUC in the ZF 5-speed ‘box) and it’s most obvious when you’re travelling at about 30mph on a slight incline on light throttle in 4th gear (around 1300rpm). It sounds like you’re driving over a series of (quiet) cattle grids. Does this sound like your problem?

You can confirm it by closely watching the rev counter while it’s making the noise as the needle will be bouncing around by a couple of hundred rpm or so in sympathy with the noise. Also, if you move the gear lever into manual mode the noise will disappear as the LUC is disengaged.

The LUC only operates in this continuous slip mode between around 25mph and 56mph at light throttle openings. Below 25mph it's off completely and above 56mph it's locked solid.

Click to expand...

hi Bremble, this i exactly what my car is doing,, big question is where can i get it fixed and how much is it gonna cost.
cheers
james

Assuming you're changing the fluid & filter at the same time :

9 litres Mobil ATF LT71141 @ £11/litre = £99
Filtran filter LPW000030 = £28
Sump gasket TYF000110 = £15
Remanufactured torque converter = £225
Remove & refit transmission = 5 hours @ £55/hour = £275

Total cost = £642

I was getting the same noise on my p38 but from the front it only happened when cruising and not under acceleration or with my foot off the pedal it turned out to be the universal joint from the front propshaft it had broken maybe check yours on the rear prop shaft hope this helps

Oops, forgot the filter O-ring (TYX000100) - that's another 50p

Bemble said:

Assuming you're changing the fluid & filter at the same time :

9 litres Mobil ATF LT71141 @ £11/litre = £99
Filtran filter LPW000030 = £28
Sump gasket TYF000110 = £15
Remanufactured torque converter = £225
Remove & refit transmission = 5 hours @ £55/hour = £275

Total cost = £642

Click to expand...

hi bremble sorry missed your reply last night, so just to clarify, the LUC is in the Torque converter?
I have the oil (bought a drum of 25litres), as have tried to fix probelm by gettign my local indie to swop oil and filter out,, but it still did it,, so since the gearchanges are all smooth and theres no lights on etc,, the gearbox itself is hopefully okay, but the torque converter needs changing,, thats a bit of a reilf as i have seen preices of gearboxes at quite high starting points.. i'll approach my loacl indie to see if they fancy doing the job..

cheers James..

osgodd said:

....so just to clarify, the LUC is in the Torque converter?

Click to expand...

Yes, the lock-up clutch is welded into the torque converter

Impeller

Stator

Turbine

Rear of turbine showing LUC plate driving dogs

LUC piston friction-welded into position

Tangential driving straps double as preload springs to clamp LUC

LUC friction plate

Chatter marks on friction face of piston (presumably due to judder)

its the air susupension pump, mine does as well lol nothing to worry about honest

hI bemble, as you may have noticed I dont do many miles! The noise does appear to be evident whether in manual or automatic as far as I can tell. Everything else in your description seems to make sense though. It's a sound that is very difficult to describe. Its coming from the nearside boot, and is almost like the vibrations that would come from the base speaker if it were loose or a screw had come undone. Like a droning noise which comes and goes randomly but very deep in its sound. I've had someone sit in the boot and its not an internal noise. Could there be something else underneath to do with the drive shafts, wheel or suspension etc. Thanks again for your time.

thanks 1992lse, im familiar with that noise and its quite different to that. It's more of a booming base rumbling noise than a buzzing motorised vibration.

I too am getting this noise? Started happening in 5th gear now happening all the time? Sounds like a buffeting deep wind sound