 | Home > Puma (Tdci) > This is a new one! Any ideas? |
 
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| Caterham Member Since: 06 Nov 2008 Location: Birmingham Posts: 6298   
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BW. In my books you are the drive train guru so if you're stumped I suspect you may be out of luck - but good luck all the same.
One of the atb's at th end of its life? I've now got 2 atbs fitted. The rear diff was fitted first and wow how much slack that took out of the transmission  |
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23rd Jul 2017 9:13am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17386  
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I have to admit that the rear diff is my main suspect at the moment, though I can't immediately think of a fault which would do this. I do know that there's a lot of slop in the back axle (the ATB and HD shafts and flanges have over 100k miles on them). Assuming I get home today without a catastrophe I will pull the halfshafts and drop the diff for an inspection.
Life is never dull with a Defender! I should have said that the lurch happens at random intervals and seem to be increasing in frequency and severity, which I suppose may mean I'll find out what it is sooner. It may be heat related, possibly. |
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23rd Jul 2017 9:43am |
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| proloForêt Member Since: 16 Mar 2017 Location: Montereau Posts: 248  
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Mr Blackwolf, I agree with Mr Caterham that if you are not knowing then perhaps this is an advanced problem beyond knowledge.
I would add to this that in my previous 4x4 which was hilux I had a similar sensation - like when slowing a trailer and it push against only no trailer there! In the end this was diagnosed finally as a fault in brake. At slowing speeds it tried to seize but could not against accelerating and faster speeds. Finally producing super heat so the mechanic easily diagnosed this. I do not think same for you though as the drivetrain systems are very different, but you are more expert than me. |
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23rd Jul 2017 10:36am |
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| Paulv8 Member Since: 09 Jun 2013 Location: Milton Keynes Posts: 618 
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Diff or rear wheel bearing imo. Try removing one prop at a time to test. My friend had something similar when a front bearing started to collapse. But with the front it pulled him across three lanes of traffic.. V8 90...WIP
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23rd Jul 2017 10:43am |
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| mk1collector Member Since: 17 Sep 2009 Location: West Yorkshire Posts: 6769 
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A brake caliper starting to seize maybe? It could release when accelerating. Ray
My build thread http://www.defender2.net/forum/topic17615.html |
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23rd Jul 2017 11:15am |
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| ian series 1 Member Since: 17 Nov 2014 Location: south Posts: 3127 
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I had something very similar while on a long trip in my 300tdi Disco,
Every now and then you would get a jolt like you describe? Turning each wheel while jacked up all felt normal? Another long run, same again? This went on for a few weeks while I tried to pinpoint the problem. I brought a second hand rear diff in the end, thinking that it was going to eventually fail on me, But When I pulled the o/s rear hub, the inner wheel bearings had failed in a spectacular way, broken in to 3 parts and almost welding itself to the stub axle! Yet turning the wheel showed absolutely no sign of noise or failure!  80" 80" 86" 88" 90"
Wanted, Forward Control Anything considered. |
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23rd Jul 2017 12:40pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17386
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Thank-you all for your thoughts. I am pleased to say that I have now arrived home safely after a further 150 or so miles, with the symptoms continuing, and at present my thoughts are these.
1. The fact that it does it when under light power and not on the overrun and not when accelerating hard makes me think of my old friend the VCV. Could it be that I am getting an almost imperceptible loss of power, just enough to bang the sloppy transmission when it comes back on? The light power effect makes me think fuelling, but my gut (and the sensation through my bum) tells me this time it is not. 2. I did earlier today check that there was oil in the rear diff. Strangely, when I removed the filler plug a reasonable quantity ok-looking oil ran out. This is odd, since on the face of it there appears now to be more oil in the diff than I put in when I last changed it. The only cause I can see for this would be that water has got in, and the oil is floating on water. This would inevitably not be good for the diff, but the oil which came out didn't look water-contaminated. 3. After a 150 run on good fast roads (but at a moderate pace, not more than 50mph, just in case something locks up or disintegrates) , front and rear hubs are slightly warm to the touch, and front and rear diffs are comfortably warm, so there is no excessive friction in the hubs, brakes, or diffs. Since I can't quite shed the instinct that this is rear driveline related and I know there's something odd with the oil level, and rather a lot of backlash in the rear axle, I will drop the diff out tomorrow evening to look for clues, and while it's off thoroughly check the propshaft ujs. With the halfshafts out it is a quick job to check the wheelbearings too. At some stage I'll probably change the VCV, but I'll strip the axle first. I'll post up any findings in case someone else one day has similar symptoms. |
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23rd Jul 2017 9:28pm |
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| nickhodgson Member Since: 08 Dec 2009 Location: Zambia Posts: 174 
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Very loose or worn rear suspension bushes can give such symptoms. Its worth having a look at the bushes. 1995 300tdi Defender 90 P/UP
2011 Puma Defender 130 D/C 2000 300tdi Defender 110 P/UP 2015 Discovery 4 SDV6 HSE |
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24th Jul 2017 12:18pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20376
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Maybe consider the clutch switch, that sometimes has an effect similar to what you describe.
Mines bypassed, but it does screw things up if the switch isn't working correctly. Worth a look at anyway. $W33T $0U7H3RN $UG4R
🇬🇧ðŸ´ó §ó ¢ó ¥ó ®ó §ó ¿ðŸ´ó §ó ¢ó ·ó ¬ó ³ó ¿ðŸ´ó §ó ¢ó ³ó £ó ´ó ¿ðŸ‡®ðŸ‡ªðŸ‡ºðŸ‡¸â›½ï¸ðŸ›¢ï¸âš™ï¸ðŸ§°ðŸ’ª |
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24th Jul 2017 2:29pm |
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| proloForêt Member Since: 16 Mar 2017 Location: Montereau Posts: 248
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custom90steve very correct. I follow his advising to bypass this switch and really better behaving from the engine now. Some how the engine is in mind of own without this modify under certain times. For me the problem was a lurching forward when i triying to stop acceleration. Fixed entirely now.
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24th Jul 2017 4:10pm |
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| ARC99 Member Since: 19 Feb 2013 Location: North Yorkshire Posts: 1831 
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Mine does the same thing when S.H.M.B.O. is driving, I make her drop a gear and it stops. Don't make old people mad.
We don't like being old in the first place, so it doesn't take much to  us off.
Richard |
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25th Jul 2017 8:59am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17386
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Last night I stripped out the back axle and am presently reasonably confident that the rear diff is the problem. I have fitted a spare diff, but need to get some new halfshafts (the inboard ends of the current HD ones are in a horrible state).
I will in due course strip the ATB and inspect the internals, but at a glance there appears to have been a lack of adequate lubrication into the centre of the diff. My initial thoughts based on my earlier experiences with my first front ATB, and a quick examinatino of this one are that if you are running high mileages on ATBs then it is very, very advisable to do oil changes far more frequently than the 80k miles that LR stipulates, This diff is/was 18 months old and has done 38k miles only (I forgot earlier that I had already replaced it once). I will update this in due course, when I know that the phenomenon has been cured and the internal state of the diff. The rear wheelbearings appear to be sound, at least as far as one can tell without taking them out. |
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25th Jul 2017 9:52am |
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| Thon Member Since: 22 Nov 2015 Location: Salisbury Plain Posts: 696
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Pending the full strip down, that's rather concerning to say the least.
I know standard diffs have their problems but this seems odd, or is it just me? If the centre has been oil starved wouldn't that be due to low oil level rather than contamination, presuming it is simply splash-lubricated? I thought one of the benefits of this type of diff is that it doesn't contaminate the oil as per "old" plate-type LSDs? As I understand it there is some preload on the internals to fool it into locking with one wheel unloaded, but is that enough to contaminate the oil? Very interested to hear what you find out - this is/was one of the upgrades I was considering for mine ... |
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25th Jul 2017 10:09am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17386
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My oil level was high, perhaps half a cupful ran out of the filler plug when I removed it. The *only* explanation I can think of for this, given that the vehicle was parked in the exact same spot as when I filled the diff, is that the axle has drawn water in through the hubs or breather at some stage. The oil still looked oily, but I don't know what gear oil well mixed with water looks like.
I suspect therefore that if my symptoms were caused by the diff, as I suspect, the root cause is not any design problem with the ATB but lubrication failure caused by contamination. I wouldn't let it put you off ATBs, it hasn't put me off (and they are still cheaper than new diffs from LR)! Speaking of which, I have just bought a pair of genuine new-style, one-piece halfshafts from my local dealer. Even with a hefty discount they are eye-wateringly expensive! I am seriously considering using security bolts on the flanges to eliminate the risk of theft! |
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25th Jul 2017 12:44pm |
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