Lotus Elan

drive train knocking

PostPost by: RichC » Thu Jan 09, 2014 5:44 pm

There's a metallic knocking on the overrun/ takeup at lower revs which sounds like its coming from front of propshaft / gearbox area . It's been there in all the 5 years I've had the car on thr road & seeing recent tread on propshaft removal prompts me to ask firstly how i can identify the likely cause.
This weekend I'm about to put the motor front wheels up on portable ramps on the drive now we've some dry weather & replace the speedo cable with new one which arrived in post today so I can if required do the necessary inspecting at same time.
In all the 5 years ( only 2k miles tho!) it hasn't got any worse and there's never been any advisories on MOT certificates for UJs , but my first (amateur) suspicion is that front UJ may be source of knocking.
Do you think it be something else , say gearbox output? ('tis 4 speed)
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PostPost by: sveris » Thu Jan 09, 2014 6:07 pm

Recent thread on the Europa Group re: knock, and it turned out to be loose flywheel bolts. Just a thought.

Steve in Ohio
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PostPost by: rgh0 » Thu Jan 09, 2014 9:47 pm

Gearbox mount or engine mount
Universal joint
worn bearing for prop shaft nose in end of Gb
Overall drive train alignment wrong so hitting engine or GB somewhere
Flywheel loose
Broken clutch disk spring
Could be similar issues at the diff end also but being transmitted up the prop shaft or chassis so appears to come from front.

Get a big screw driver and carefully lever on all the components you can, to see if you can detect any issues when you are under there.

cheers
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PostPost by: oldelanman » Fri Jan 10, 2014 6:59 am

As Rohan says check the rear end as well......propshaft to diff flange bolts, diff tie rod bushes and exhaust contacting the chassis.
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PostPost by: PeterK » Fri Jan 10, 2014 7:05 am

...or exhaust
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PostPost by: RichC » Fri Jan 10, 2014 8:22 am

Thanks folks . I'll keep u posted
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PostPost by: alan » Fri Jan 10, 2014 8:54 am

i had a clicking noise on a +2 . It was a rotoflex bolt with wear in one of the diff output shafts. Normaly the 3 holes should be a sliding fit but one had worn the hole bigger
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PostPost by: Chancer » Fri Jan 10, 2014 10:17 am

You can eliminate the loose flywheel, even the slightest bit of play combined with the inertia and cyclicle acceleration/decelerations will rapidly increase until it sounds like all the bearings are shot and/or the crank has snapped (been there done that), I am talking of minutes at high RPM, no way could that noise continue for 5 years.
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PostPost by: Chancer » Fri Jan 10, 2014 10:18 am

Cush drive springs in the clutch pressure plate perhaps?
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PostPost by: billwill » Fri Jan 10, 2014 11:51 pm

You can feel/see the front U/J through the hole in the side of the tunnel.

Take out R/H seat and the plastic cover of the tunnel. There should be a hole or flap in the carpet.

If you jack up the rear you can then test for a worn U/J by getting someone to rock one of the rear wheels to & fro.
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PostPost by: kstrutt11 » Tue Jan 21, 2014 10:45 pm

The similar knock on mine turned out to be a diff top mounting fractured at the bolt hole to the chassis, I understand this fairly common.
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