JCtx

Hi gang. My '12 (manual) GS has a weird issue since day 1, but I thought it was just the mechanical clunk of the gears, like when you shift gears with the engine off. It sounds exactly like that now, but it's louder, and lasts longer, as the temperatures drop. And it's only on the 1-2 shift when cold; zero clunks on all other gears, hot or cold. I wouldn't call it grinding or clashing, since it's momentary; therefore I'm calling it a clunk or crunch. But maybe at higher (cold) rpm they'd grind worse; who knows. And the weird part is contrary to most Tremecs, my tranny is easy to shift into 2nd, except that it crunches instead (wish it was the opposite). And the even weirder thing is I don't feel anything on the shifter, nor does it kick back or have to force it into gear... I only hear the clunk below the tunnel, with the stereo off. Don't remember exactly when it started since I usually had the stereo on. And now that's cold, it keeps doing it for miles, rather than the 1/2 mile or so when it was warm.

Here's some more info. Car just crossed the 3K-mile mark, never abused, never launched, never shifted quickly, and never grinded any gears (other than this cold issue). Changed tranny fluid to Amsoil Torque Drive Dexron-III fully synthetic (what the factory recommends), but made no difference in that regard. It's hard to shift into gears all the way when cold and engine not running, and it clanks when forced all the way. But it shifts perfectly when hot. Recently started depressing clutch pedal all the way when shifting into 2nd cold (typically do it about 90% down), and it made a bit of difference, but still crunches. All other gears make zero noise, and shift smoothly hot or cold; just a bit notchy when cold, as expected. Clutch grabs about half way on the pedal travel, meaning it's disengaging perfectly. And yes, I've been changing the reservoir fluid since day 1, about 7 times now. I shift around 1.5K to 2K rpm when cold (and mostly hot too). Even tried shifting at 6 mph, which puts 2nd gear right at idle, and still clunks. The clunk is only marginally louder with increased revs, which is weird too. With clutch disengaged and car going slower, I assume the clunk is not wearing the synchro's teeth too much, is it? And the better question is what the heck can be causing that? An improper blocker ring gap, or wrong pre-loading on one of the shafts? And why only when cold? The service manual troubleshooting guide doesn't have anything specific on that; only when it happens all the time.

Finally, even though tranny shifts perfectly when hot, I checked the shifter box anyway, since it's part of the troubleshooting process. Removed the shifter box yesterday, opened it up, and everything was perfect. Lubed it real well, and reinstalled it with the neutral pin locked, and tightened it to the 22 ft/lbs specified in the manual. Did the rod's collar at the very end, to assure nothing was stressed. And gears still don't go in smoothly with engine off, but haven't driven the car yet. There's nothing else to check/adjust externally. I don't anticipate any changes, based on no improvements when dry shifted. Manual says tranny should shift smoothly when off, but my car doesn't. And neither did most of my previous cars, by the way. In fact, some gears just refuse to go all the way, until I can engage others fully first. Then when I go back, it's hard to shift again. They keep changing like that. But the true test is with the engine running, of course. I plan to do that tomorrow, after I buy some Dynamat to take the opportunity to insulate the center console.

I'd appreciate some words of wisdom. And yes, will park my car overnight at a local dealer one of these days just to document it, but won't do anything until the problem is obvious all the time. Still have the hope it'll get better, since nobody seems to know what the hell the problem is. And only happens when cold. And can't shift car when off, but shifts perfectly when hot. And predict will be the same after the 'adjustment', but will update you with that. Hey, what happens if I use the car with the entire center console off, meaning F55/AH-TC/hazards/heated seats/USB-Aux/12V-receptacles disconnected? Thanks gang.

JUIC3D

My advice of taking it to the dealer and having it documented still stands.

Regarding driving the car around with the center console out--that's not a problem. I've done that numerous times on my car when doing misc things(nitrous install, etc) and it does not cause an issue. The car still runs perfectly normal.

JasonS5555

Yeah, you're going to have to get it documented. Possibly more than once.... Without that they're not going to do anything.

Jason

JCtx

Do you have F55? I don't want a code set that I can't erase with my OBD-II reader.

Yes, as I mentioned, if problem persists, will leave car at dealer overnight one of these days and drive a tech to document it. But am not worried about being covered under warranty; car has 5-yr powertrain warranty. I just don't want the transmission removed, period. And certainly not before there's trouble shifting to 2nd all the time, meaning the problem won't go away for sure.

Anyway, just wanted to know if somebody else has this issue, and most importantly for me, WHAT CAN IT BE. Main shaft too tight? Having trouble shifting all gears all the way (that last 1/4" where synchros mesh) randomly when dry (engine not running), should mean something, no? Again, I don't consider that abnormal, but if all other T-6060 owners can do that in weather, it must mean something is not quite right inside the tranny. But the real test will be driving the car when I finish installing the Dynamat. It'd be extremely rare that something as simple as a blocker ring or gear is defective, especially when everything is perfect when hot. I'm sure it's a tolerance problem somewhere, but would like to know where, and if there's any possibility of going away on its own as tranny breaks in. Still, I'm going to keep using it until it gets better or worse. And if worse, will let somebody else deal with fixing the tranny and trade-in the damn thing. But will keep playing with it to find more clues. Downshifting is always perfect, but I always rev-match on downshifts. Will try downshifting without rev-matching when cold and see what happens.

Oh, and manual tranny owners, drive your car when cold without the stereo on. More of you might have the same issue, but don't know it. I'll also try the stereo on and see if I can hear it, and volume needed. Shifting at very low rpm might not harm anything, but that clunk certainly shouldn't be there. If nothing happens to the tranny, I'd keep the car. Otherwise, it'd be gone, and it'd be my last GM ever (had issues with the other 2 I bought with the stupid piston-slap and excessive drivetrain noise). On this, the engine is fine, but the tranny is not. And read it has always been a 'well known' issue since it came out in 2008; unbelievable. Have a great day gang.

JUIC3D

No F55 here but I can't imagine it setting a code that isn't removable with a scanner or battery disconnect.

JCtx

Guess it makes sense. Since it wouldn't be an emissions code, doubt the scanner can clear it. But a battery disconnect should. I think the default mode is 'sport', but no biggie for 15 miles or so.

Will try it then. With that hole open, I'll be able to hear loud and clear what's going on in the tranny, and how loud the 'clanking' actually is. Will attempt to record it with a small digital camera I have, and shift at 2K rpm the first time, even if it bangs harder than usual, so you guys can hear what I'm talking about. Will keep you posted.

JCtx

SUCCESS!!!!!!! YES, YES, YES.

Just came back from a test ride after adjusting the shift box, and tranny shifted: PERFECTLY!!!!!!!!

I wasn't optimistic because I was having an even harder time engaging gears with the engine off than before (service manual says we should be able to do that). Well, as soon as I fired up the engine, I could shift ALL gears like butter. Yeeehaaa. Looking good, since I could never do that before the car started moving, especially 1st and reverse. By the way, removed the F55 **** and TC/AH switch from the center console and hooked them up before firing up engine, to avoid a code not erasable by an OBD-II scanner. And yes, I opted to fully remove them rather than just leaving them on the passenger seat. It'll make the Dynamat installation much easier .

Started driving, revved engine to 2K+ rpm, which I never do cold, expecting a big 'bang', so you guys could hear it on the video, and ZERO NOISE. Perfect shift. And like butter; smoother than ever before, and garage was at 50ºF. All shifts were perfect. No notchiness whatsoever, and ZERO gear clash, so erased video. Maybe the Amsoil fluid I just put 100 miles ago had something to do with it. The only thing I noticed was shifts were a bit noisier when cold (expected), and that 2nd gear needed full clutch disengagement to be less balky, even when hot (remember 2nd gear/synchro is different that all others on our tranny). But shifter felt absolutely PERFECT. Don't understand why people want to replace it. Perfect throws, and it has a very nice mechanical feel. And after hearing the racket with the tunnel open, no way I'd install an aftermarket shifter now, since they're not nearly as well insulated, due to the modification needed on the stock insulators.

Bottom line, I HIGHLY recommend that you align your shiftbox; it takes minutes with the center console removed. And you can take the opportunity to 'Dynamat' all that area to minimize heat intrusion into the center console and tunnel, and minimize noise even further. A nice 1 to 2-hr project folks. Honestly, my shifter might have been misaligned maybe a millimeter tops. But it made all the difference in the world. Now this is the best transmission I've ever sampled, even better than the ultra-expensive Graziano on the Aston and Ferrari. Those lack the mechanical feel this one has. Now it shifts like freaking butter, cold or hot. If not, change your tranny fluid to fully synthetic Amsoil and it should be just like mine. I'm super happy that I won't have to sell my car . Have a good one folks.

HOW TO ALIGN SHIFTBOX: To align it perfectly, all you have to do is this: Push the neutral lockout pin in front of the box down to make sure gear shift lever is locked in neutral. It's going to be hard to initially move it since there's a detent. If you can push the pin down, there's probably no need to do the procedure, but takes a minute, so I'd do it anyway. After shifter is locked in neutral, loosen rod collar T-40 bolt first, then loosen the other 2 T-40 bolts that hold the box in place. Tighten the 2 box bolts to 22 ft/lbs. Then tighten the rod collar bolt also to 22 ft/lbs. THAT'S IT. I did remove the box to check everything inside, and lubed everything, so if you're up to it, just do it. It'd be a lot easier to install the neutral lockout pin that way too. It's a no-brainer to put it back on. Can't screw up the installation; it's practically impossible. Even a chimp can do it. If you need video instructions how to remove the center console, look for the MGW shifter instruction video. Hope this helps folks.

Bill Dearborn

Why would you worry about a code not resetable by an OBDII scanner. The code would disappear as soon as you hooked things back together. Don't worry about things that don't make a difference.

Bill

JCtx

A friend knowledgeable on this issue (owns an '11 GS and a service manual) told me to better hook them up. And no, I don't worry about things that don't make a difference. But things that CAN make a difference and I don't know, I play it safe . Took me 5 minutes to remove and connect. And no resetting/reindexing hassles. Plus possibly needing a dealer to reset it. You try it next time . And thank you very much for your great help; geez .

JUIC3D

Glad to hear of the great news.

camirocz

Next time just go to the dealer its not worth getting grey hair over it.Your car is a 2012 on warranty!!!!!!!!!!!

JasonS5555

Good news! And I do understand why you would want to do the work yourself. I've had way to many issues with them damaging my vechicle during warranty work....

Jason

Bedouin

Ditto on not taking it to the dealer as I avoid them whenever possible, not to mention the DIY knowledge & experience gained.

If I understand the issue correctly, you only needed to realign/mount the stock shifter box correctly as it was misaligned/loose from the factory?

Glad it all worked out!

JCtx

It's the opposite for me man: I'd have gotten gray hair by going to a dealer .

Yep, story of my life, so don't do that unless absolutely necessary. Plus I really enjoy working on my vehicles, and nobody is going to care better for them than I do. I'd of course give a dealer the benefit of the doubt, but only when I have no other choice. Most of the local dealers have never worked on Corvettes, so being the owner of the car, possessing the same manual techs have, having an engineering degree, having worked on cars all my life, and having the right tools, makes me at least equally qualified as them for jobs not requiring heavy equipment . And finally, even qualified techs, they make their money by doing a job as fast as possible, not as thorough as possible. And THAT is my main beef with the industry. I probably take 3 times as long, if not longer, but do it perfectly, taking all the precautions to not damage/scratch/stain/scuff/etc. the car in any way. And most of the times, when I have to strip something, I also like to improve the car if possible. This time I'm installing Dynamat to reduce heat and noise in the center console area. And also put crazyglue on the clips' hooks, since they're always damaged when pulling any of the POS panels GM makes. Once removed once, they have play, even if you put a new clip, since the plastic from the panel is damaged, and part can rattle. Also check everything around, and ziptie, cushion, or do whatever necessary if parts/cables can make noise. Nobody is going to do that for you at a dealer. Have a great day folks.

JUIC3D

Post up some details about this 'crazy glue' mod. I'm interested to learn your tips/tricks for a quiet interior.

JCtx

That alone doesn't quiet things any more buddy; it's just to refit the panels like factory. When you pull any panel with those crappy GM clips, they 'bite' into the plastic as you pull on the panel, and therefore move in and out at least a millimeter after removal, and that can create rattles. The harder you have to pull, the more they bite into the plastic. And if enough force is exerted, the clips stay in their slot, and the panel tab gets gouged up all the way out. And you cannot position the stupid clips in a different position. Lousy design; they're only meant to be installed, and never removed. I just put a drop of loctite on every 'hook' tip, so the clip doesn't move in their newfound groove. I'm not even sure this works, but it should .

To quiet the interior, or eliminate currrent/future rattles, I check all harnesses around and put zipties, foam tape, or whatever necessary to make sure nothing rattles/squeaks/creaks when moved. Just a precaution. Hope this helps.