Hello Forum!

My first post here, although I've been lurking for some time... I'm impressed with the tone of this forum and the knowledge displayed, so, as seems to be the usual case, my first post is requesting help with a problem...

2004 V8 Auto Disco II
277000 km (171000 miles)

Symptoms:
Rough idle and rumbling noise appearing at 80 -100 kph in drive at about 2000rpm. Down-shifting to 3 increases revs to about 2500rpm and rumble reduces. Main stealer charges U$60 to diagnose fault codes 300, 304, 332.

Replace plugs and fit Magnecor leads (Thanks to the gent that posted the quick fix without removing IM. 45 minutes without secondary air).

Engine runs smoother at idle - no visible 'samba' i.e. the engine is no longer rocking from side to side at idle. Road test shows that 'rumble' problem persists. At about 80 kph (50 mph) in 'D', 2000 rpm, there is a distinct rumble that can be felt and heard. It feels like a very bad misfire. The vehicle seems to be stuttering forward (Difficult to describe!). Down-shift to '3', revs increase to about 2500 rpm, and the rumble reduces but does not disappear. Accelerate to 100 kph (62 mph) in '3' and there is no noticeable increase in 'rumble'. Change up to 100 kph and the rumble/stutter returns, albeit at a lower frequency.

Initially I thought engine, however, while the engine runs noticeably smother following the plugs and wires change, the rumble/stutter is still there. Prop shafts? I figure that the rumble would not change frequency with a gear change as prop shaft speed would remain constant. So I'm leaning towards the autobox. Now here's my problem: I'm pretty competent mechanically, having spent 27 years working on helicopters, but I know the square root of naff all about autoboxes....

What does the forum think? I'd prefer to chase down the low dollar possibilities first (as opposed to the main stealer approach). I have an unavoidable 400 mile round trip in the car tomorrow, and hope to hell I get back in one piece to read the responses.

First response will probably be: "Whatever you do, don't drive the car!!!"

TIA,

Mark

 

If you are at the rumble speed, and shift to "N" and engine rpm drops to idle, what happens to rumble? Up to date on tranny fluid and filter changes? All fluid levels OK? What about diff fluid levels and grease for front swivels? Transfer case fluid change up to date and level OK?

Surging forward - slipping tranny? Engine RPM changes fluid pressure inside tranny...

BTW - free download of the RAVE tech manual, if you don't have it. Not enough time this afternoon to study up on rebuilding automatic gearbox.

 

Thanks for the fast reply.

I'll slip it into neutral and see what happens. I didn't mention that the problem is worse under load, reducing slightly as I lift off the throttle.

I'll check fluid levels and report back - these have not been changed during my ownership.

Could diffs cause this? The problem occurs at a reasonably constant rpm - 3rd gear, 80 kph, 2000 rpm, and D, 100kph, 2000 rpm. Changing up at 80 kph or down at 100 kph alters revs and seems to reduce the rumble/stutter, although road speed stays constant. This is why I had discounted diffs and prop shafts (their revs would not change regardless of eng rpm for a given speed), and was beginning to suspect the autobox or, as you point out, the transfer box.

400 mile trip about to start, so if it gets back in one piece I'll be happy...

 

Muscat, is it a rumble or a slight vibration? You might want to check the rubber donut on the tailend of the rear propshaft. If if has cracks in it, however slight, it might be causing vibration/ rumble through the drivetrain at certain speeds. good luck. Phil

 

Well she got me back in one piece, but wasn't happy.

Savannah Buzz, slipping into neutral all vibration disappears. How do I check for a slipping transmission?

ljdiscovery, the donut looks to be fine - no obvious cracks or other damage. As to whether it's a rumble or a vibration, it's both! Difficult to describe - sometimes it feels like poor road surface at other times you can hear and feel a low frequency droning harmonic that causes the complete vehicle to vibrate. I would guess the frequency to be about 2 per second. This can also be felt through the diff lock (I have a disco 1 CDL fitted, so I imagine the mechanical linkage transfers the vibration better than the cable operated D2 version).

I carried out the stall test described in RAVE, only reaching 1700rpm, which suggests my engine is low on power. Not sure if this would be contributory?

Given that the noise / vibration disappears when slipping into neutral, I'm tending towards transmission or transfer box. Does this seem reasonable? I'll try a fluids and filter change and see if there is any improvement...

Thanks for the replies, Gents.

Mark

 

I too have a little of this.. I noticed my front ball joint seals gone... and Im just about to do tranny fluid and transfer case... if it stops raining on my days off! lol I get that rumbly feeling "not sound in my case just a slight whine around transfer case through interior harmonics " For me around 35mph and maybe I felt it a little approaching 70mph... I also have a buzzy whine from Im thinking one or both of the idler pulleys ( tentioner pulley already changed with belt )... overall it is pretty smooth just that little rumbliness ... to me it feels loose.. the driveshaft is rebuilt with all greasable HD ujoints and ball...

 

My problem was eventually traced to a dodgy spark plug. I had changed all plugs and wires previously, so looks like I fitted a duff one... Since changing the plug the "rumble" at 80 kph ish, rough idle and hesitant acceleration have gone.

'course, a few weeks later the radiator sprung a leak, and the front passenger door decided it would not open from either inside or outside...

 

hmmm... I might check plugs and wires again... I do not get any codes from misfires... but i suspect thats a possibility.... that and maybe time for transfer and tranny refill and ball joints and then shocks and springs and... lol

 

Well... Ironically, I was trying to trace down fuse to see why my windshield washer dont work.. none of them, and looking around under dash fuse panel, I noticed one of the relays was a slight bit cockeyed ( 2nd yellow one from bottom ) hmmm... disco ran SUPER SMOOTH to work... no slight stumbling around... hmmm... also a note, I did reseat a few other fuses , I did however remove and check each of the relays on under hood fuse panel.. al seems ok so dont know if I fixed anything or not... lol but sure funning GREAT! not even any 35mpg rumbling or loosness... weird..

 

Just finished my transfer case refill and made a little short video of what I did... I used a 6" wobble extention 1/2" rachet and it fit perfect... and I went to hardware store to get a 1' long copper tube easy to bend and stick it on the end of the hose from pump and pumped it right in no problems at all..

2003 Land Rover Discovery Transfer Case Refill - YouTube