2000 Disco 2, original owner, 172k, new OEM engine in 2009 under warranty at 92k. Regularly serviced, no engine oil leaks, no coolant leaks, changed all fluids in 2023, old fluids all looked normal. After-market drive shaft with serviceable U-joints.

Up to 45 mph, the car is dead quiet. Over that speed, I start to get noises, both a low rumble and a high pitched whine, which get louder as speed increases. The rumble is much more of a problem. I can take it up to 90, but it’s very unpleasant to drive with that much noise, and even over 55 is very loud. When it was new, the drive train was so quiet that I could unknowingly find myself driving 90 and have no idea I was driving that fast.

There is no noise when I rev the engine in neutral. Just the beautiful sound of an engine revving.

Plenty of tread on the tires, though the rear ones are six or seven years old (no signs of cracking in the sidewalls).

Around 2011 one of the diffs (I think it was the rear) was switched out for one from a donor car, and that reduced a very loud high pitched whine at that time. The recent whine is much less noticeable.

Last year, part of the angled portion of the exhaust heat shield tore off.

Any thoughts as to how to what the cause of the noises might be, or a procedure for diagnosing them?

 

Check the oil in the diff and transfer case, and check your drive shaft, and do it before you do any more driving you may have a very very bad day

 

Bad vibrations - crappy driveshaft ie AB or LK8 - been there myself and probably half of the ppl on this forum). Unfortunately you have to shell out for a proper one ie Tom Woods or GBR

Whine - worn out t case, or something is rubbing on the spinny parts ( I had one of the random unused connectors undo itself from a bracket on top of the t case and it was rubbing against the parking brake drum making a pretty loud hissing/squeaky noise. Not sure how is that even possible, but then it's a disco)

 

Aftermarket front or rear driveshaft? Guessing front, right? Is it a cheapie?

First thing I would do, since it's a 2000, is remove the front driveshaft and lock the center diff with your handy 10mm open end wrench. Drive it. Cheap front driveshaft IMO is always a suspect component for noises such as what you are describing. If noise persists, this test would remove both front driveshaft, and front diff from the equation.

This would then leave:

Transfer case
Rear driveshaft
Rear differential

 

I very much appreciate all your comments. I will reply to each of them. First, let me note that although I have learned a lot about my LR through this forum, I am not a mechanic, so bear with me if I ask naive questions. Second, my car is serviced by a mechanic friend who is a former fleet mechanic, has his own fully stocked four bay shop (with lift) in his backyard, and has done excellent work for the past six years. He is not a LR specialist, but is a natural mechanic. I assist him on the work he does, and I have witnessed all of it.

1. We changed the diff and transfer case fluids in 2023. He put new fluid in until it started running out. There are no leaks. But I will ask him to check it.

2. NashVegas: My Disco does not have a locking differential accessible from the driver’s compartment. Are you saying that it can be locked regardless from underneath the vehicle?

3. I first replaced the front driveshaft with a GBR around 2010, after reading about the problem here. The first one they sent me was badly out of round, and we sent it back to be fixed. I had that in the vehicle until about 2018, when I started experiencing loud noises on the drive train. I bought a LKY8 and my current mechanic installed it, and the problems remained. He then removed the rear driveshaft and reinstalled it, and the problems went away. I’m not sure which front driveshaft we put back in the vehicle. I did save the other one. I tried to upload photos of it (in the hope that someone could identify which one it is, so I would know which one is in the vehicle), but the upload feature kept stopping at 90%. Are there identifying features on the two driveshafts that would enable me to tell which is which?

4. My friend did visually inspect the driveshafts the last time he serviced the vehicle two months ago, and they seemed fine to him. What should we be looking for to tell if they are going bad?

 

Ok, in thinking about it a little more: the driveshaft in my shed looks virtually new, and I’m pretty sure it’s the LKY8. Once the 2018 noises were resolved, I recall having my friend reinstall the GBR front driveshaft, on the theory not to fix what ain’t broke.

If that’s right, then the GBR has been installed for about 14 years and 80,000 miles. Do these tend to wear out over that length of time?

 

Are you tires balanced?

 

If the unjoint weren't greased often, they might have worn out after 80k - especially on the front where the grease gets baked by the cat.

You can lock your t case by putting the car into neutral and reaching on top of the t case to turn a little protruding "bolt". You won't be able to see it, it's way up there.

 

Yes. They’re Michelin M+S. These noises don’t sound like they’re coming from the tires.

 

We grease the joints regularly.

Not sure what locking the transfer case does. If we lock it and the noise persists, does that mean that it’s not a problem with the transfer case?