smart51
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| posted on 5/9/06 at 07:08 AM |
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drive line clonk
My car has started to make a clonking noise when I open or close the throttle quickly. If I roll on the power it is fine. Actually, I can't so
much hear it as feel it.
I quickly lifted the bonnet last night and turned the prop by hand from the engine end. The box was in neutral. There seemed to be 5-10 degrees of
backlash in the prop.
What are the potential problems, other than diff backlash and a loose prop?
Is it going to be a big problem or should I not worry.
For info, I have a sierra LSD and an R1 engine with a two-piece prop and no reverse box.
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Agriv8
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| posted on 5/9/06 at 07:24 AM |
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A couple of things worth checking if you havent already.
Diff to chassis bolts loose
Lobro joint bolts
regards
agriv8
Taller than your average Guy !
Management is like a tree of monkeys. - Those at the top look down and see a tree full of smiling faces. BUT Those at the bottom look up and see a
tree full of a*seholes .............
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scotlad
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| posted on 5/9/06 at 07:55 AM |
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I'm having the same problem since fitting my new engine. Chatting to a mate, he suggested the much sharper throttle response of the new engine
might be a contributing factor, sao i'm going to try fitting a heavyish spring to the throttle pedal to see if it damps it a bit. Its always
clunked, but it seems to be getting worse. prop bolts etc are all tight......
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mcerd1
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| posted on 5/9/06 at 08:06 AM |
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I'd say the prop uj's the most likely culprits - the bearings could have gone
worth checking anyway
If it is the prop uj's they are easy fixed if you can get the propshaft off the car
[Edited on 5/9/06 by mcerd1]
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Tangerine Scream
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| posted on 5/9/06 at 08:17 AM |
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I have the same driveline (apart from a ZX9) and mine does the same.
I'm sure someone brought this up on the forum before...and from what I can remember about reading the discussion, it didn't unduly concern
me so it must have been OK 
fingers in ears..... lalalalala
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Phil.J
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| posted on 5/9/06 at 08:25 AM |
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Sounds like it might be prop.u/j's. DO NOT ignore these if this is the case, a flailing prop in a car like this could be very unpleasant!
Phil
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Tangerine Scream
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| posted on 5/9/06 at 08:41 AM |
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Mine's definitely not the prop as the backlash is apparent at both the diff input and the sprocket adaptor in the same amount. The prop is only
20 miles old too.
I've found the thread I originally read at
link to thread
Sorry for appearing so blase about it 
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DIY Si
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| posted on 5/9/06 at 10:17 AM |
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Mine does this on part throttle and when you lift off. Ive checked the prop as best as I can and it just seems to be the backlash in the diff and
gearbox. It also isn't helped by having everything solid mounted and right next to you. Every little thing feels much bigger when it's
bolted next to your kness!
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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Hellfire
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| posted on 5/9/06 at 11:54 AM |
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TRT prop will go a long way to curing your problem 
Phil
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matt.c
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| posted on 5/9/06 at 07:07 PM |
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Helfire, what is a TRT prop like and who sells them, also how much is one?
Cheers
matt
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Hellfire
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| posted on 5/9/06 at 08:08 PM |
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Torque Resilient Tube. Basically, it's a tube within a tube and the two bonded together with rubber. Dunning & Fairbank modified our MK
propshaft for about £125 IIRC which involved replacing the rear section with TRT, fully balanced and even painted
Hang on while I go get a link for Dunning & Fairbank........................
Here you go - Link
[Edited on 5-9-06 by Hellfire]
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smart51
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| posted on 5/9/06 at 08:18 PM |
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So the most likely thing is diff backlash. I'll check next time I'm in the garrage. Will this problem only get worse? Will the diff
brake? Is the backlash caused by knackering the teeth on the crownwheel and pinion or by backing the pinion out a bit?
I can see how a TRT might slow the problem but I guess that it won't cure it. Am I right?
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Hellfire
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| posted on 5/9/06 at 08:34 PM |
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My guess is that it's just normal diff backlash. Once you get used to driving a car and become more comfortable with it, you pick up on noises
that have always been there - you've just not really noticed them before. I would also imagine that it's quite difficult to break a diff
in a seven style car under normal use, given the weight of the car that it originally had to propel.
You're right though, it won't cure the problem with the driveline clonking, it'll just be far less noticeable and not so harsh a
take up on your gearbox, which can be beneficial for engine longevity.
Phil
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smart51
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| posted on 5/9/06 at 09:50 PM |
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Thanks Phil, that's rassuring.
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