Vehicle & Technical > Discovery

300TDI Clunk only with diff lock engaged and driving.

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crazymac:

--- Quote from: "boss" ---first thing that springs to mind is "transmission wind up".(stopp me if im wrong) the idea of fitting a centre diff is so the car can tirn around corners as the front and rear wheels spin at different rates while turning(because the circumfrance of the front wheels is greater than the rear while turning).
the obvious problem with this is that while offroad the centre diff will distributr power between the axels differentley which isnt what you need(bare with me im not trying to teach you something you alredy know) so the centre difflock is imployed which negates the original application off the centre diff, so if you were to turn a corner with the diff lock in the forces applyed on your running gear are enormous, usually what happens things will twist a little then work its self out while spinning in mud ect.worst case scenario this could snap half shafts, cvs, propshafts, ujs, kill your gear box or your centre diff. it doesnt usually happen in discos more in the series models but i would say thats what happend. did you turn on tarmac atall?
--- End quote ---


Slightly right! when going around a bend the wheels turn at different speeds side to side, not front to rear! so therefore the centre diff allows this to happen and not "wind up" the transmission.

When off road you lock the centre diff so that the power is distributed evenly, so if one wheel has traction then that will help get you out. equally if you have wound up the transmission then it can unwind by spinning in the mud (or generally loose surface)

Where people make mistakes is they automatically engage diff lock just cos they are off road! Thats not good as you could be on solid ground. Diff lock should only be engaged when you are "likely" to loose traction.

If the clunking or twanging is not present when you run straight in diff lock, it would suggest that it is not transmission wind up unless off course it has solved itself already, when you had this happening what sort of terrain were you driving over? if the axle was articulating it is entirely plausable that the bottom securing plate has come loose (rusted!!) and so when given the opportunity the spring will waggle about.

try jacking the body as high as you can ( a highlift jack would help here) so the axle dangles and you may see?

otherwise as you say, sort out the lift and have a look then!!

Lugslandrovers:
Thanks
No this happened just i as i started through the off road course although it was quite a hard surface in places. But you do have me thinking. Maybe it got wound up on the hard surfaces. I pulled out before the end of the course onto taramac and it did it then. I stopped changed to high diff/normal and was ok no knocks or twangs. Just tried it this afternoon twenty yds on tarmac forward and reverse up the kerbs and no noise.

SteveGoodz:

--- Quote from: "crazymac" ---Slightly right! when going around a bend the wheels turn at different speeds side to side, not front to rear! so therefore the centre diff allows this to happen and not "wind up" the transmission.
--- End quote ---


When cornering all four wheels are rotating at different speeds. If the front to rear speed was the same then the centre diff wouldn't be needed. The axle diffs enable side to side speed differences.

boss:

--- Quote from: "SteveGoodz" ---
--- Quote from: "crazymac" ---Slightly right! when going around a bend the wheels turn at different speeds side to side, not front to rear! so therefore the centre diff allows this to happen and not "wind up" the transmission.
--- End quote ---


When cornering all four wheels are rotating at different speeds. If the front to rear speed was the same then the centre diff wouldn't be needed. The axle diffs enable side to side speed differences.
--- End quote ---


exactly!

crazymac:

--- Quote from: "boss" ---
--- Quote from: "SteveGoodz" ---
--- Quote from: "crazymac" ---Slightly right! when going around a bend the wheels turn at different speeds side to side, not front to rear! so therefore the centre diff allows this to happen and not "wind up" the transmission.
--- End quote ---


When cornering all four wheels are rotating at different speeds. If the front to rear speed was the same then the centre diff wouldn't be needed. The axle diffs enable side to side speed differences.
--- End quote ---


exactly!
--- End quote ---


I won't argue cos I don't know enough :wink:  I was always told the difference was side to side, but I suppose there is some sense in front to rear as well??

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