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Discussion Starter #1
Summary: One explanation for a phantom bad smell might be seeping gearbox oil.

Details:
When my 2011 NA's original CR gearbox blew four years ago at 40k miles, I got the chance to learn about the weak intermediate gears that appear in at least a significant minority of early CR 'boxes.

Although there are repair and replacement options available now, at the time my most cost-effective approach was to swap in the complete power pack (engine/trans) from a wrecked '10 that I happened to have laying around. IIRC the new-to-me transaxle had 10-12k miles on it at the time of the swap. I also took the opportunity to do a short-shift modification, which transformed shifting on the car -- so in the end the busted transmission was something of a blessing in disguise.

Anyway, at 57k miles on the car now, in other words at a bit less than 30k total miles on the replacement transaxle, I have discovered a gear oil leak. I first noticed the distinctive smell a couple of days ago, and this morning finally saw some evidence of oil on the bellypan. Not enough to drip, but it's enough that I'm parking the car up for now -- although I could probably go for a while without running much risk of damaging the box, I feel it's better not to risk it. Guess the convertible will be coming out of storage a little early this year! ;)

I have a supercharged engine swap planned for the Evora later this year; I think I will move that up a bit, and also take this chance to rebuild one of the early CR boxes I have laying around with an uprated gearset. I'll try to remember to take some photos for the forum when I do that. (I'm rebuilding another car right now, so it'll probably be summer before I get to the Lotus.) So for now, I'm not going to bother rectifying this leak, since this 'box will just go on the shelf ultimately.

In the meantime, I just thought I'd post a note here in case it's useful to others. If you've got a higher-mileage car, and are noticing a sulfur smell but no oil drips in the driveway, you might want to pull the bellypan for a gander. I don't know for sure, not having had mine on the lift yet, but I would bet that the fix is as simple as new seals on the diff (i.e. where the axles go).
 

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I could swear there was discussion of this before, where there is a plug for an unused fitting (trans cooler line?) on this transmission and people were having some small amount of seepage out of that plug. Any chance that's what you're seeing?
 

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Discussion Starter #3
Could be. Could also be a really badly failed input shaft seal I suppose; won't know for sure until I dig into it. From what little I could see looking down into the engine compartment, though, it looked to be happening around the lower diff, though of course that may not be indicative of the origin.

I don't recall seeing a trans cooler blank plug anywhere on the gearboxes I've looked at, but it's been a while since I had one in my hands. If you happen to come across that thread again, let us know -- a couple quick searches didn't turn it up. (Although it's funny how many threads come up with the keywords "leak" and "trans" or "oil"... ahem.)

In any case, since we occasionally get "what's that smell?" posts here I thought I'd post the above as a potential item to check out.

Again, the takeaway is: even if you don't see oil on the driveway, a gear oil smell might indicate that you have oil seeping from the trans. And pulling the bellypan is the only way to figure out precisely where.
 

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Discussion Starter #7
Thanks for that, I remember those threads now. It's possible that my oil is coming from somewhere in the upper part of the trans, as described in those threads, but I have to say I'm (still) skeptical. The shift mechanism cover is an unlikely place for a leak, given its design and placement, and as for the nylon bit, it is also well above fill level and unlikely to see a failed o-ring.

But again, just speculation until I get around to looking, in a month or two or three.
 

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Man that is no fun! Sorry to hear your having to rebuild your box again.

When you say 'uprated gearset' - do you mean higher strength gears, different gearing, or what?
 

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please do full write up with pictures if possible on tackling.. clam removal etc, i have an 2010 and dreading the day..im actually planning on purchasing some upgraded gears and tackling preventative upgrade later this year , ( tired of it being in the back of my head ) i also want to add a supercharger as well
 

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Discussion Starter #10
Man that is no fun! Sorry to hear your having to rebuild your box again.
When you say 'uprated gearset' - do you mean higher strength gears, different gearing, or what?
See link in first post to Monkey Wrench's replacement gearset.

I only mentioned my previous transmission faffing so that someone wouldn't think I was trying to keep it quiet and accuse me of being a secret gearbox murderer.

please do full write up with pictures if possible on tackling.. clam removal etc, i have an 2010 and dreading the day..im actually planning on purchasing some upgraded gears and tackling preventative upgrade later this year , ( tired of it being in the back of my head ) i also want to add a supercharger as well
I was planning to do my forced induction and other upgrades in 2017 when I collected all the parts, but got distracted with a cross-country move, a new house, and blah blah blah. Right now I am rebuilding another car, and then I probably need to put a new engine in my old shop Sprinter, and then I'd really rather work on some of the vintage cars than dig into the Evora.... so in short, it might be a while before I get to the Lotus. Sorry.

The workshop manual has all the needed detail on pulling the engine -- it really is very easy to follow. The only point on which I didn't follow the factory book was in not opening the AC piping. But however you do it, as long as you pay attention to where all the little bolts and wiring connectors go, it's not hard.



[Off topic: Unless you have an Evora 400! I read here recently that there was a newish Lotus dealer near my new home in Oregon, so today I headed over there to check out the three 400s they had in their showroom. Had a look under the decklid, and whoa. I'm sure the extra horsepower is nice, but man, the engine room sure looks like a plumbing nightmare. No offense to anyone who drives and enjoys their plumbing nightmare.]
 

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Hey thank you - sorry I had missed the hyperlink in the text of your post. That MWR gearset link is interesting and they mention a 10% lower "Sport final drive gear kit"? Now THAT is what I am interested in!
 

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See link in first post to Monkey Wrench's replacement gearset.

I only mentioned my previous transmission faffing so that someone wouldn't think I was trying to keep it quiet and accuse me of being a secret gearbox murderer.



I was planning to do my forced induction and other upgrades in 2017 when I collected all the parts, but got distracted with a cross-country move, a new house, and blah blah blah. Right now I am rebuilding another car, and then I probably need to put a new engine in my old shop Sprinter, and then I'd really rather work on some of the vintage cars than dig into the Evora.... so in short, it might be a while before I get to the Lotus. Sorry.

The workshop manual has all the needed detail on pulling the engine -- it really is very easy to follow. The only point on which I didn't follow the factory book was in not opening the AC piping. But however you do it, as long as you pay attention to where all the little bolts and wiring connectors go, it's not hard.



[Off topic: Unless you have an Evora 400! I read here recently that there was a newish Lotus dealer near my new home in Oregon, so today I headed over there to check out the three 400s they had in their showroom. Had a look under the decklid, and whoa. I'm sure the extra horsepower is nice, but man, the engine room sure looks like a plumbing nightmare. No offense to anyone who drives and enjoys their plumbing nightmare.]

It is a mess
 
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