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#Post#: 103449--------------------------------------------------
is it possible for a timing chain to jump a tooth when worn unde
r heavy deceleration?
By: Ed Straker Date: April 25, 2025, 3:38 am
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As the topic title suggests, i had been putting off a fan belt
change for a little while as I thought it may have been a duff
alternator bearing.
concurrently the engine has started shaking after a person
braked heavily in front of me on the motorway.
I have ruled out the alternator and water pump. Still shakes
when belt removed to eliminate these two sources.
Changed engine mounts as they were worn to eliminate this issue
in case the engine shifted on the emergency braking.
Still shakes.
Have checked compression and tappits - not headgasket or broken
springs.
Vacuum gauge shows a steady needle.
Changed spark plugs and HT leads.
Still shaking.
I am at a loss, maybe I need to check static timing.
Any suggestions?
J
#Post#: 103450--------------------------------------------------
Re: is it possible for a timing chain to jump a tooth when worn
under heavy deceleration?
By: Ed Straker Date: April 25, 2025, 3:48 am
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2.25 petrol 3MB obviously.
#Post#: 103452--------------------------------------------------
Re: is it possible for a timing chain to jump a tooth when worn
under heavy deceleration?
By: kev Date: April 25, 2025, 1:35 pm
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Sorry, can’t help you, have you Goooogled it?
#Post#: 103459--------------------------------------------------
Re: is it possible for a timing chain to jump a tooth when worn
under heavy deceleration?
By: Ed Straker Date: April 26, 2025, 6:59 am
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yes, google is not my friend.
Back to basics then with a green bible to check static timing.
#Post#: 103464--------------------------------------------------
Re: is it possible for a timing chain to jump a tooth when worn
under heavy deceleration?
By: Theshed Date: April 27, 2025, 4:32 pm
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Highly unlikely to have slipped a tooth.
Two things come to mind, could one of the brakes be sticking and
give the shaking feeling ?
Or. Could it be a misfire. Timing issue could be elsewhere, such
as points.
Happened to me once in a Fiat, hit a pothole and the base plate
moved.
#Post#: 103465--------------------------------------------------
Re: is it possible for a timing chain to jump a tooth when worn
under heavy deceleration?
By: Sunny Jim Date: April 27, 2025, 7:10 pm
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If it is a misfire, taking each plug lead off in turn should
identify it. If it gets worse after removing a plug lead, then
that one is not at fault, if it makes no difference, then there
is a problem on that cylinder.
I would go through the ignition system, checking the points,
timing, lead etc. Static timing is fine to get the engine
started.
You could also have dislodged some shit in the fuel, that is now
causing a problem?
It might be worth doing the 'sucking thing' on the carburettor
intake. Take off the air cleaner pipe at the top of the
carburettor, star the engine and up the idling speed a little
(not a lot!). Then cover the air intake on the carburettor with
your hand, of better still, a flat piece of wood. This will
usually clear a blocked jet.
Sunny Jim
#Post#: 103467--------------------------------------------------
Re: is it possible for a timing chain to jump a tooth when worn
under heavy deceleration?
By: Ed Straker Date: April 28, 2025, 10:21 am
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Thanks Sunny and Threshed,
Spent the day going through the ignition and timing, no luck. (
I got zapped so maybe the HT leads do need some attention)
Swapped out the Carb for a known good spare - improved at idle
still shakes on drive.
Went through the tail shaft universal joints - back UJ at rear
diff has a great deal of movement - have I found it?
Have taken a spare tailshaft of a scrapper and will fit tomorrow
- fingers crossed that it was a combination of the two issues.
I am in Aust so 12 hours different to you lot. Will report back.
#Post#: 103468--------------------------------------------------
Re: is it possible for a timing chain to jump a tooth when worn
under heavy deceleration?
By: Theshed Date: April 28, 2025, 11:27 am
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Could you remove prop' and run in front wheel drive to check
rear shaft issue ?
#Post#: 103469--------------------------------------------------
Re: is it possible for a timing chain to jump a tooth when worn
under heavy deceleration?
By: Ed Straker Date: April 29, 2025, 6:17 am
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I could, but it was just as easy to swap the shafts over and go
for a test drive.
Problem sorted. Started raining needle bearings when i took it
off. Amazing how much vibration is transferred to other places.
Still got to look at my timing chain one day but at least it
will be on my terms hopefully.
#Post#: 103470--------------------------------------------------
Re: is it possible for a timing chain to jump a tooth when worn
under heavy deceleration?
By: Theshed Date: April 29, 2025, 8:30 am
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Well done, thanks for letting us know. :thumbs:
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