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Discussion Starter · #1 ·
This seems to be a common problem, but my '05 Elise now grinds when downshifting from 3rd to 2nd gear at very high RPMs (i.e., while on the high-cam). I can still get the shift done, and if I double-clutch and throttle blip twice (once when moving the shifter into gear and again while releasing the clutch), I can avoid the grind entirely. The problem only happens at higher engine speeds. I've got 21K miles on the car, of which something like 4000 miles were done on the track.

I'm betting the problem's attributable to a bad synchro, and I've bought a new C60 gearbox from Toyota. My question is what's caused the problem? I'd hate to go through the effort (and cost) of installing a new gearbox only to go through the same problem again!

Note that I've never damanged a gearbox before, I'm proficient with heel-toe, and I've got a lot of track experience in various cars. One suggestion I've heard is that the transaxle oil might be overheating, which suggests that more frequent changes might be called for (mine was changed yearly).

Any other ideas?

Thanks,
Twin
 

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If you think it's fluid rlated, do you think Blackstone could confirm it by analyzing a sample?

The slop in the shifting mechanism combined with engine movement has always made me wonder.
:shrug:
 

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If you think it's fluid rlated, do you think Blackstone could confirm it by analyzing a sample?

The slop in the shifting mechanism combined with engine movement has always made me wonder.
:shrug:
+1 That would be my suspicion too. Before I stiffened up the shifter mount, the shifting action was the sloppiest of any car I've owned. I feel there's still an issue shifting at high engine torques, as the engine/transmission rotates quite a bit when the clutch is disengaged. Stiffer engine mounts are next on my list of mods...
 

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Discussion Starter · #4 ·
Thanks, Codymac and APK919 for your posts. I suppose I could have the fluid tested, but it's been changed several times, including not too long ago when I tried (optimistically and in vain) to "solve" the grinding problem by replacing the fluid. The movement of the engine/transmission seems as if it could certainly impact shifting, but I'm not so sure why only the 3rd gear to 2nd gear shift seems to generate grinding.
 

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Thanks, Codymac and APK919 for your posts. I suppose I could have the fluid tested, but it's been changed several times, including not too long ago when I tried (optimistically and in vain) to "solve" the grinding problem by replacing the fluid. The movement of the engine/transmission seems as if it could certainly impact shifting, but I'm not so sure why only the 3rd gear to 2nd gear shift seems to generate grinding.
I think it's because the 2nd gear synchro is exposed to the highest loads... in fact there's even some detail in the manual about it:

Lotus Service Manual said:
On 6-speed transmissions, in order to cater for the heavy demands made on the second gear synchroniser,
and provide high durability, this gear is fitted with a double cone mechanism to increase the conical surface
area within a small space.
 

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Discussion Starter · #6 ·
That makes some sense. Thanks for sharing!
 

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This may seem obvious, but you should double check that your shifter linkage/gates are well aligned... Also, I make it habit to rev match on the down shift even just around town to 'help' the longevity of the syncos- especially 2nd and 3rd since they get so much use and abuse...

Good luck,

Phil
 

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FWIW, you don't necessarily have to abuse these trannies at all. I didn't with mine and, off the top of my head, neither did Rugbyduck.
 

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This may seem obvious, but you should double check that your shifter linkage/gates are well aligned... Also, I make it habit to rev match on the down shift even just around town to 'help' the longevity of the syncos- especially 2nd and 3rd since they get so much use and abuse...

Good luck,

Phil
Well... it depends on what you consider "rev matching"... if you push in the clutch, change gears, and <b>then</b> blip the throttle to rev match, you're still relying on the synchos to mesh the gears at different rotational speeds (which of course causes synchro wear). If you double clutch, matching gear speeds before engaging the synchos, then you do reduce synchro wear...
 

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Well... it depends on what you consider "rev matching"... if you push in the clutch, change gears, and <b>then</b> blip the throttle to rev match, you're still relying on the synchos to mesh the gears at different rotational speeds (which of course causes synchro wear). If you double clutch, matching gear speeds before engaging the synchos, then you do reduce synchro wear...
Yes. Thats why I always double clutch in street driving. On the track I just rev match since I'm not able to double clutch fast enough :(.
 

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FWIW, you don't necessarily have to abuse these trannies at all. I didn't with mine and, off the top of my head, neither did Rugbyduck.
+1. I drove this car the same one I've driven all my previous cars, in fact, perhaps not as hard, and this is the only one that I developed the synchro problem in.
 

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driving habits change

I am speaking purely from personal experience and not suggesting this is your problem...

I have been driving for over 50 years. I learned to drive wheat trucks, no synchro, and have always enjoyed double clutching down the gears. I know about matching revs perfectly as double clutching incorrectly rewards you with lots of sound.

I even wrote a shifting explanation for my sandsmuseum website!

Lotus Elise Experience, How to Shift Gears

I find that I occasionally get lazy and shift as I depress the clutch. I also find in the heat of the moment on the track, that I miss shift or again, drag the clutch. Both of these will put extra pressure on the synchromesh. By honestly and carefully examining my driving habits, I increase the time between moving the shifter and releasing the clutch.

I might want to think I have the experience and the skill, but I find I can always improve.

My experience, your mileage may vary,

Michael
 

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Yes. Thats why I always double clutch in street driving. On the track I just rev match since I'm not able to double clutch fast enough :(.
I double clutch my downshifts most of the time to preserve my synchros as well, despite all the crap I get from people about it (most manual drivers don't know the first thing about driving manual anyway).
 

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All right, after a long hard 3 day track session at Spring Mtn, I now have this same problem with 2nd gear synchro failing....can anyone tell me about how much it costs to fix/replace tranny? (I'm out of warranty...)
 

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All right, after a long hard 3 day track session at Spring Mtn, I now have this same problem with 2nd gear synchro failing....can anyone tell me about how much it costs to fix/replace tranny? (I'm out of warranty...)
Don't shoot the messenger; but, IIRC, it's on the order of $7K (mine was under warranty). Surferjer would know for sure I'd think.
 

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All right, after a long hard 3 day track session at Spring Mtn, I now have this same problem with 2nd gear synchro failing....can anyone tell me about how much it costs to fix/replace tranny? (I'm out of warranty...)
On the "glass half full" side of things, if it's just the second gear synchro, it won't affect you at Big Willow at all... no second gear turns. Even if you had to downshift to second, you can double clutch the downshift and single clutch all the other downshifts...
 

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Don't shoot the messenger; but, IIRC, it's on the order of $7K (mine was under warranty). Surferjer would know for sure I'd think.
-eek-:(:mad::evil::panic:

On the "glass half full" side of things, if it's just the second gear synchro, it won't affect you at Big Willow at all... no second gear turns. Even if you had to downshift to second, you can double clutch the downshift and single clutch all the other downshifts...
Yea, I thought about the upcoming LCS #3 at Big Willow - no 2nd gear necessary, so I should be ok for that event....or else, as you say, I'll have to learn double-clutch....what a pain.
 

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Discussion Starter · #18 ·
FWIW, I found (at Sears Point last week) that if I hesitate slightly on the downshift, putting just enough pressure on the shift lever to "suggest" the transaxle that I want to shift into second -- without forcing it and causing it to grind -- that I can still get into second without any grinding. It just takes a split second of hesitation and then slips into gear. That said, I've got a transaxle sitting in my garage awaiting an install. You can buy a Toyota C60 gearbox (identical to the C64, save a taller 6th gear) for Celica GTS for about $2K. Be sure to also replace the throw-out bearing and clutch disc while you're at it. Those parts are cheap.
 

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Is there anything more heavy duty that we can do to help stop this problem in the future?
 

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Straight cut gears?
 
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