Lotus Elan

Differential Clearance & Vibration

PostPost by: jrmdir » Wed Mar 02, 2005 3:10 am

My S1 has long been suffering from a harsh, high frequency vibration on overrun or trailing throttle. I finally inspected the diff mounts and it appears that the bottom front of the large diameter (banjo) section is almost touching the chassis. On overrun it would seem that the torque reaction would try to lower the front of the diff and close the tiny gap that exists.

If this is indeed what is happening, I have the choice of removing one of the spacer washers (there are two) from each of the top mounting lugs to raise the whole unit, or perhaps trying to shorten the lower mounting rods in order to raise the nose of the diff. Does anyone have any experience with this sort of problem? Are there any other potential causes for the vibration? All rubber mounts and bushings are in good shape with very low mileage but are more than 10 years old.

Thanks
jrmdir
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PostPost by: Foxie » Wed Mar 02, 2005 1:30 pm

Hi jrmdir (?)

Before adjusting any clearances it would be a good idea, after more than 10 years, to renew all your mounts and bushes, and check that the chassis is not damaged. Have you been able to have a good look at the top mounts, not only may the rubber be in poor condition, but the lugs can break off. You also need to check that the chassis has not cracked at the mounting lugs. I've had to do a body lift on both my Plus 2s to repair such damage and fit a reinforcing strip.

Sean Murray
68 Elan +2, 70 Elan +2s
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PostPost by: nebogipfel » Wed Mar 02, 2005 7:30 pm

Another thing to check is has the car been jacked up under the chassis below the diff lugs and been bent or damaged?

I agree with Sean about the bushes especially the torque arm bushes and also if any have been contaminated with oil and have gone soggy
John

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PostPost by: jrmdir » Wed Mar 02, 2005 9:05 pm

Thanks to both of you for the quick responses. I'm going to get new rubber parts as a starting place and then try to maximize the clearance and will let you know what happens.
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