Greetings all.
Here I go. 2003 Discovery 2 SE, automatic, US version (left hand drive) Stock everything. Vehicle has 225k miles. It has developed a drivetrain noise I can only explain as a clacking noise (?) This sound is apparent at any speed above a couple MPH and does not improve or degrade at higher speeds. Shifting into nuetral however will cause the sound to stop even though the vehicle is still moving. (coasting) If I am accelerating the noise is there or if I'm decelerating (Engine introduces drag to drivetrain, it is there) However in that weird middle spot it will sometimes go away. (hard to get very far like that!) Now, what have I done? My experience said front propshaft. So I ordered a new one and installed it, nothing changed. (old one appeared good upon inspection) I suspected fluids and it was time for those services anyway so I drained and serviced front and back diffs, and the transfer case. Since I was under there I also dropped the tranny pan, cleaned up and put in new filter and Orings and fresh fluid. No change. I dropped the rear driveshaft and rebuilt the UJoint and replaced the Rotoflex coupler, (even though they appeared fine, won't hurt) no changes. There were no apparent signs of shavings or trash in any of the drained fluids and the catch magnets were the usual, nothing egregious at all) I have scratched my head a lot and looking for direction. I think I know the answer but really dont want to swap a transfer case? Any thoughts?

 

First, if you shift into neutral while sitting still and rev the motor, does it make the noise?

Second, if you put the transfer case in neutral and the transmission in gear does it make the noise? CAUTION! When attempting this, shut the motor off before re-engaging the transfer case OR before shifting to park.

 

Alex M
Nuetral and rev motor; no noise
Transfer case in nuetral, tranny in drive, rev motor. No noise

 

Just curious, does it do it in reverse? Does the tempo change with speed? Does it change with engine rpm? To determine the difference, start in first and then notice how the noise changes in each gear. Does it do it in low range?

You can jack the truck up, put one axle on jackstands, chock the wheels, cdl unlocked, put it in gear and the wheels will roll. Put it in Forward when you do the rear axle, you can get under the rear of the truck. Put it in reverse when you do the front axle, you can get under the front. Make sure whatever you do not put yourself in a position where the truck can drive over you. Do not get under the truck between the wheels with the truck in gear. Doing this you might be able to identify the noise.

 

I'm unsure if it does it in reverse. I dont think it does? But I will check in the morning for sure. As for the speed change(?) yes. It gets faster with speed and seemingly louder as well although, it really seems to be two levels of noise; initially softer and slower, then at 10mph its louder but thats it basically I think because of faster tempo? I will do as you suggested in the morning and report back here. Thanks for the help!

 

Ok, couple more recommendations.

First, put the truck in low range. See if it starts sooner, is the same, or doesn't start at all.

Second, with the truck chocked and in neutral (truck off) go underneath and just start feeling for play at the differentials, transfer case outputs, and wherever else you can get your hands on.

Edit: looks like Extinct beat me to the punch on the low range, and made other good recommendations as well.

 

Does the noise change at all if you turn wheel from side to side at road speed or turn hard lock while moving forward? Thinking maybe C/V joint?

 

Extinct,
Okay here we go!
It does not seem to do it in reverse (unless it's so faint I cant hear it?)
Tcase in High, 123D no change
Tcase in Low, 123D no change (sound is consistant through all gears both high and low))
Hard left and hard right does not increase or decrease noise.

 

The Deputy,
Hard left and right (all the way to lock) doesn't seem to have any effect good or bad?

 

Alex M,
The sound remains the same whether High or Low on the tcase.(and through all gears) Does not seem to make it in reverse though. The only "slop" I seem to be able to locate is in nuetral and I can turn the Ebrake drum a little (?) maybe a couple inches or so in either direction. It does however seem to be more difficult to shift the tcase than previously required. Not undoable, just seems tighter to me?