Lotus Elan

Sizzin' Gear Stick

PostPost by: gjz30075 » Fri Nov 12, 2004 10:01 pm

My car, being a '72, came with the two piece anti sizzle gear shifter and I changed it out 25 years ago for a solid stick and never looked back. Feels great and it never really sizzled.

Recently, I upgraded the motor (different block) to a stroker, now running 1720 cc's. I now have a REALLY annoying gear shift sizzle between 65 and 75 mph. It's there at steady throttle and goes away upon acceleration or decel. Not fun for highway cruising. What relationship changed here to cause this? Going back to a two piece stick is NOT an option. I'm looking at changing the shims under the cap that holds the stick down but there's not much else to change. Any ideas?

Greg Z.
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PostPost by: nebogipfel » Sat Nov 13, 2004 7:25 pm

Greg this is unlikely I know but I don't suppose the rubber gaitor has split has it? Mine had quite a small split and the noise increase was significant.

The other thing I have done (not on an Elan) is fitted double gaitors. I know it's a bit of a bodge but it does cut down noise assuming there are no significant mechanical problems.

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PostPost by: types26/36 » Sat Nov 13, 2004 8:08 pm

Greg,
Out of interest why is going back to the original anti-sizzle gear lever not an option ? I have never heard off problems with that set up.
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PostPost by: tmr » Sun Nov 14, 2004 4:05 am

The earlier non-bushed shift levers have a much more direct feel than the later style. If you haven't tried one of the earlier ones, then the old one feels fine. After driving Greg's car with the earlier shift lever, mine felt downright sloppy. I now have the earlier one-piece arrangement. The only time I notice any 'sizzle' is when the 'hood' is up. Otherwise, wind noise masks it.

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PostPost by: types26/36 » Sun Nov 14, 2004 10:13 am

Tom,
I have both, non bushed on my S2 and bushed on my Sprint so I know how both gear change feel. I dont prefer one over the other its just different so I suppose its a matter of personal choice, I just thought Greg must have had a problem at some time with the bush.
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PostPost by: gjz30075 » Sun Nov 14, 2004 12:27 pm

Brian, you're right, really. It is a different feel and I really prefer the solid stick. But the problem is, why the change?
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PostPost by: types26/36 » Sun Nov 14, 2004 5:02 pm

Greg,
I'm no expert on such matters but I would think several factors and it may be not just one thing that have played a part in your "sizzle" As you said you have upgraded to a different engine which in its self could be a factor was the engine balanced? no doubt you have changed or at least moved the engine/gearbox mountings/exhaust system and any of these could contribute/cause a vibration/resenation to manifest itself through the gear lever at a given rev's/speed. There was in the Elans day an issue with this as Lotus themself brought out the bushed gear lever for this exact reason, I can't offer any advice on how to cure it except to suggest a propshaft balance and maybe check/replace
engine/gearbox/diff mountings. An other point to check would be to ensure the diff has clearance at the bottom and is not touching the chassis.
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PostPost by: type26owner » Sun Nov 14, 2004 5:36 pm

Most likely the detent surfaces and springs in the gearbox are showing their age or were never up to the task from the beginning. Sounds like you've got inertial coupling caused by you disturbing the vibration source by changing engines so the easiest solution is to try and detune it. Simpliest thing to do is to try clamping a pound or two onto the gearshifter and find the sweetspot which might just cancel the sizzling. Lead is ideal for this purpose and can be slide up and down for getting the moment out of phase. If that does it then have a leather cover stitched together which covers up the shifter to the knob and call it good to go.
Good luck!
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PostPost by: type26owner » Thu Jan 27, 2005 7:45 pm

Hey Greg,
I just recently developed the very same sizzling noise but it's not the gear lever doing it. Just started happening after I upgraded the gearbox flexible mount to the S3/4 style stiffer one. Have noticed new fatigue cracks where there never was any before on sheetmetal stuff attached to the engine too. I called today and ordered two new S1/2 wimpy style mounts to put it all back the way it was without the sizzle on my S2. Suspect I've tuned the driveline and/or the chassis to resonant at it's natural frequency with the stiffer mount.
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PostPost by: lotus026 » Thu Jan 27, 2005 8:34 pm

Being that I own several cars that all have aquired a sizzling shift lever over time with modifications; I agree that the changes you did with the new engine are likely to have caused it - you could always try putting the old engine back in and it would probably be gone! But in the normal course of events, you've modified the engine to improve performance; that usually is at the expense of other things such as increased vibration, that's what I ended up with on a couple of my cars once I'd bumped the HP up by modifying the engine. The easiest way to change the sizzle is to either damp the shift lever or change the mass of it, so that it'd vibrate at a different frequency; a great way to do both is to try slipping a chunk of rubber hose snuggly over the bottom of the shift lever; it'll tend to damp the vibration while still allowing the direct feeling of the single piece lever. Might even manage to get one (or maybe a couple of chunks, one over the other) at the base of the lever under the shift boot so it doesn't show, I'm sure it would at least change when the noise happens.
Good luck!
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PostPost by: gjz30075 » Thu Jan 27, 2005 8:55 pm

Thanks, guys. I do like the gearbox mount change idea, because, I, too, have developed cracks in the crossmember. I guess I never put 2 and 2 together in this case.

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PostPost by: type26owner » Sat Jan 29, 2005 9:16 pm

Hey Greg,
Looking at the two different types of mounts and it's obvious what the problem is here. Yes, the S3/4 is stiffer but the real biggie is it's mounted in there so the direction of compliance is 90 degrees out of phase from the S1/2 one. Well no duh, that's why the damn thing is vibrating like hell. It's trying to resist the force the engine mounts are there for instead of allowing the engine mounts to do their job. It's over-constrained when the 6 DOFs are considered which defeats the primary purpose of the elastomer mounts. The lower chassis bracket is torsionally compliant to allow a range of motion so the engine mounts can be elevated to the right height so their bolts line up with the chassis attachment points If the mount is rotated by 90 degrees. I'll bet all the later cars have this problem. Dumb, dumb, DUMB!

All is not lost. If you make an adapter plate to rotate the S3/4 mount 90 degrees then it will be oriented correctly to allow the NEEDED compliance in the correct direction. Probably another adapter will have to be made to reconnect to the chassis bracket. You can do this if like on the S2 the bottom beam bracket bolts onto the bottom of the chassis. Just place some spacers there to provide the vertical room for the new adapters. The mount is assymetrical somewhat in the cross-section area of the elastomer from one side to the other. Best guess is the side with the most rubber elastomer should go on the exhaust side because the engine/gearbox rolls toward the carbie side when at WOT. That's the side which is being placed in tension or being stretched somewhat.

I'm going to but the S2 mount back in. Always in rush and not paying enough attention to the fundamentals results in Three Stooges type of engineering getting installed on my car. I really should know better. Yuk, Yuk, Yuk.........
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