Lotus Elan

Metallic rattle

PostPost by: 2cams70 » Mon Apr 08, 2019 11:50 pm

Is your car fitted with the 4 speed Ford box or the 5 speed Leyland based box? On the Ford 4 speed the gear on the mainshaft driving the speedometer is steel and not plastic.
1970 Ford Escort Twin Cam
1972 Ford Escort GT1600 Twin Cam
1980 Ford Escort 2.0 Ghia
Peugeot 505 GTI Wagons (5spdx1) (Autox1)
2015 Honda City 5spd.
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PostPost by: Harvey » Tue Apr 09, 2019 12:32 am

It's the Ford four speed. I'm sure you're right and that I am confusing it with the plastic gear that lives in the speedo angle drive.
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PostPost by: alanr » Tue Apr 09, 2019 8:01 am

I certainly would not go shortening the Propshaft!...Do not do it!
If as you say the propshaft yoke is bottoming out and hitting the mainshaft then something is wrong with the location of the engine/gearbox or differential not being mounted in the correct place in the chassis. Lotus I am absolutely sure certainly did not build your propshaft too long!
Alan
'71 +2 S130/4
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PostPost by: Craven » Tue Apr 09, 2019 10:55 am

2cams70,
Later 4 speed gearbox has a plastic ( Blue ) mainshaft speedo drive gear.
speedo-gear.jpg and
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PostPost by: Harvey » Tue Apr 09, 2019 5:52 pm

Alan,

I feel certain that the prop shaft is original to the car ('71 Plus 2S). I've owned the car for 20 years and in that time have driven it about 30,000 miles. The only potential change in the distance between the diff flange and the end of the main shaft would be attributable to the fitting of a Spyder chassis back in 2004. Thousands of trouble free miles have been logged since then. Engine mounts and diff torque rod rubber bushings are all good and the torque rods are tightly secured allowing no diff movement forward.

Why then, was the main shaft pushed forward into contact with the input shaft with enough force to displace the main shaft snap ring? A possibility posed by my mechanic is that the prop shaft is too long and somehow allowed the yoke to apply pressure to the end of the main shaft. While the yoke does not have as much clearance as my mechanic would like to see or that of an Elan I measured, the difference is small and still leaves almost 1/2" of movement when fitted before the yoke contacts the rear of the main shaft.

However, as I have tried to explain above, I cannot take a chance that the yoke might, in the future, come in contact with the main shaft. Since I am going to have the prop shaft balanced anyway I might as well have it shortened to make sure the prop shaft is beyond reproach. Even shortened by 1/2", the yoke still has plenty of support in the tail shaft. Moreover, I'm adding lightness to the car.

Lee
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PostPost by: joe7 » Tue Apr 09, 2019 7:17 pm

I don't think the prop shaft displace the circlip. Its more than likely the force on the circlip because it was installed incorrectly. If the circlip, which is tapered, isn't properly fitted into the beveled groove on the mainshaft it has a natural tendency to dislodge. How do I know? Because the 2 that I rebuilt had the circlip installed backwards.
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PostPost by: Harvey » Tue Apr 09, 2019 8:12 pm

Joe,

I hope that's the case because I have been assured that it is fitted correctly now.
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PostPost by: rgh0 » Wed Apr 10, 2019 2:16 am

If the gearbox output shaft is accidentally hit while handling and fitting the gearbox into the car that could also dislodge the snap ring especially if it was fitted incorrectly in the first place.

If the gearbox is installed attached to the engine and it accidentally swings and hits the chassis during the installation this sort of problem could arise.

cheers
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PostPost by: Harvey » Tue Apr 16, 2019 7:03 pm

Rohan,

Thanks for advancing a theory I hadn't thought of. However, I just had a chance to discuss this with the mechanically experienced guy who was handling the tail shaft under the car during installation of the engine/gearbox and he assured me he was being very careful to make sure the end of the shaft did not impact the chassis. Thus, it is still a mystery as to why my mainshaft snap ring was displaced and mainshaft was in contact with the input shaft when the gearbox was disassembled.

I will return to this conversation after I get the prop shaft shortened and get the car back on the road.

Lee
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PostPost by: gavk » Sun Apr 21, 2019 9:49 pm

Andy Hay

Very long thread so forgive me if you've solved your issue or someone has posted this already.

I had a similar sound occuring under similar circumstances, I found it was a screw up collar on my propshaft.

See my thread for photos and details:
viewtopic.php?f=37&t=40196&p=280280#p280280

Hope for your sake that it's the same issue, Easiest of fixes, Jack car up, tighten by hand, job done!

Please bear in mind that my car has an MT75 gearbox so your propshaft may not have the collar in question, other members may be able to advise.

Thanks

Gavin
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