Yeah, you would feel it more in time with the engine rather than moving forward. I didn't totally rule that out, but it's a lot less likely based on your description than the other causes posted.

 

Sounds like it could be one of your tires to me..drive very slowly (5 mph) in a straight line on a smooth road and feel for a bump from one the tires, sometimes its the simple things...the frequency of the vibration would be a clue

 

I am having this same issue on my 03 with 128k on the dash and definitely feel your pain. My wife is also suggesting we get rid of it because she thinks its too much of a money pit.
I too have also replaced the driveshaft with a grease-able one less than a year ago and keep it lubed religiously. I checked for hub looseness and found nothing out of the normal. The driveshaft is really secure with no play up/down/left/right. Just tonight I tried lifting the front two wheels and put transfer case and tranny in neutral while spinning the front tires and could not get it to replicate the thumping noise I am hearing while driving. My thump is equally bad in reverse as well and increases with speed.
Just out of curiosity, did you ever have a slight chirping noise present with the thumping on your vehicle?
I am going to replace my newer front propshaft with the old one just to see if it continues but I have a feeling after hearing that you replaced yours to no success, I probably wont either. I am leaning towards a transfer case issue because when I spin the front wheels with the transfer and tranny in nuetral it doesn't make that sound/thump. The front diff would still be rotating right?
I dont think it is tranny related because wouldnt it be slipping? So that leaves just the transfer case.

I will also try to troubleshoot this problem and post my findings. Please keep us updated on your progress also.

 

unfortunately, i have not been able to do any diagnosis/testing yet this week. People actually expecting me to work...

I can't say i've heard the chirping noise, but it's been too cold to ride w/ the windows down since this has started happening, so i haven't really had a good opportunity to test.

As for your diagnosis about the tranny case, yes, the front diff would still be rotating - so it could be the tranny, but you also haven't completely eliminated the idea that it is the wheel/tire/hub (or any piece factor that requires pressure on the tire).
I am still really curious to see if swapping my front tires changes anything; i literally just have not had the 15 minutes it takes to jack it up and swap them out...

 

i had the same kind of noise and thought mabe drive shaft too but it turned out to be a heet sheild hannging down from the floor and hitting the turning drive shaft hope this helps good luck

 

I don't know about the original poster but mine is definitely driveline related, no question about it. I just can't figure out what driveline component it is yet. I will get to the bottom of it but I started a new job and also have very limited time available to troubleshoot the source.

 

Ok, had a little time this weekend to lift the entire truck off the ground and get all for wheels spinning and I cant replicate the noise to save my life. As soon as I put her back on the ground it starts with the noise/thump/click problem again. The CV's look ok on the outside and the boots aren't torn. This makes me think it is hub/bearing related again since when lifted in the air, it has no pressure on the wheels/tires. By the way, I lifted it in the air using jack stands on the axle housings so the suspension would still be compressed.

 

If its a wheel hub there should be play in the bearing. I assume you checked that, but it passed that inspection?

 

There is an inspection cover on the bottom of the bell housing that you might want to check out to see if you notice anything unusual. I believe there are 3 8mm bolts holding on the cover.


There are also two rubber plugs in the oil pan that you can pull to inspect the flywheel.

Since you can't make the thump while revving the engine in park, and you can't recreate the thump by turning the wheel by hand then I'm leaning toward it being a transmission or T-Case problem. Did you ever check and change the transmission and T-Case fluid?
You might be able to VERY CAREFULLY raise all 4 wheels off the ground and put it in drive and have someone give it some gas while you look for the source of the thump.

 

Just an update, I purchased a new wheel hub assembly since land rover made it a good idea to not be able to service just the wheel bearing and makes us buy a whole new assembly. I will post results after install.

For reference, I have swapped out driveshaft with old unit that did not clunk before and it still clunks. I have tried the "lift the whole truck off the ground" test and could not replicate the noise. I have also visually checked everything under the front suspension where the noise it coming from and tried the wiggle test of each front wheel to check hubs.