Hey Guys,

Anyone else experience issues with 1st and 2nd gear? 3 - 7 is smooth as butter but 1 and 2 seem to be a PITA. I can feel a crunch, notch, grind going into each. Yet if I sit at a stop light, clutch in, and go 1, 2, 1, 2, 1, 2 back and forth it gets smooth. Its a 2014 with 20K miles and I bought it in July. 2nd gear is the only gear where it will pop out of gear because I didn't fully engage it all the way. You really need to slam it into 2nd to make sure it's in all the way. Not sure if this is normal or not. And doesn't matter if car is cold or hot. Would different trans fluid fix this?

Thanks

 

Lot's of folks have reported a 1-2 "nibble" when cold.It should be fine in a few miles.

I found that changing the fluid also helped mine some.

Do a search and notice what Bill Dearborn has to say about this issue.

\db2

 

My 2014 z51 with 24k miles, is like what you describe. If I drive about 30 miles, it warms up the trans oil enough that it shifts fine first to second. In cold weather I sometimes have to skip 2nd and go to 3rd. When putting it in 1st or 2nd (when cold) I have to wait for the second click going into gear or it will jump out. I'm going to try changing the fluid soon to see if that helps.

 

My 2014 z51 with 16k miles has the same issue. It grinds bad from 1-2. It is harder to get into gear when cold, but still grinds when warm. I've taken it to the dealer multiple times and they cannot find anything wrong with it. I bought a MGW short shifter, but that did not solve the problem. My next step is going to be to change the transmission fluid.

 

2016 Z51 M7 13K miles, same thing here. Dealer says it's withing parameters, or something like that. Had them change the trans fluid but I think it only helped for about a day. I've learned to live with it for now.
For normal driving I found you can avoid the grind if you shift slowly, that is, after you press the clutch in, delay a second or so before shifting it into second.

Was also thinking about the MGW shifter, but as mentioned, it doesn't help so I've avoided that.

HTH,
Pj

 

I installed a MGW shifter right after I bought my car. I like the shifter and the shorter throw. Doesn't fix the hard shifting.

 

So this is damage accumulated on your tranny, and it doesn't happen during upshifts, but rather during downshifts. If you're feeling vibrations during the shift, especially when cold, it's fine, synchromesh gears are doing their job. If you feel outright grind, however, it means that you synchromesh gears are no longer effective in syncing gear speeds. These are very high torque cars with relatively high weight, and the transmissions come with big gears to withstand it. As such, they can't be rushed during shifting, or the gears and synchros start taking a beating.

Another important point to mention is rev match feature. If the car did the rev match before transmission gears are ever engaged during the downshifts, you'd likely never have this issue. However, the rev match in Corvettes only engage when the synchromesh gears are already engaged (you can feel the vibration of the engagement before the rev match), and as such, the transmission is not protected (only engine / remaining driveline is). If you, however, blipped the throttle yourself at neutral before your downshifts to the neighborhood of the expected RPMs, you could've greatly increased the life of the synchros, and keep your buttery-smooth transmission. Since this has to be done in neutral, it's also called double-clutching, which is used to increase the speed of the main shaft (Neutral is still connected to transmission shaft).

Anyway, long story short:

• Shifts (especially downshifts) in any manual car with high torque engine cannot be rushed. Don't let the rev match fool you.
• It is the downshifts that cause most of the damage, so focus there if you want to keep your tranny buttery-smooth.
• Car's rev-match feature helps, but only to a small extend.
• You can do most of the work done by synchromesh gears by merely double-clutching and getting the engine to the target RPM range. You get used to it, but if it's too complicated, just shift to neutral, blip, and then engage clutch, shifting down to the gear.

 

Do you by any chance(For lack of better terms.) shift like there is no tomorrow?

We had a young man bring his 2017 Grand Sport in to Weapon-X in June with the same symptoms.

This ended up being the problem:



I showed him, he said he wasn't easy on it. I recommended ordering a new one, and sending it off for to have it cryo treated. He did that week, we installed it along with a MGW STS. Haven't had a problem since.

 

It's only happening under normal shifting. Wind to about 2k rpm's in 1st gear and shift into 2nd. It did it worse when it was new. It's not a bad grinding noise like you let the clutch out too soon. After it warms up it shifts great. But it takes about 30 miles in warm weather before it shifts ok. It seems to be fairly common from what I've read here on the forums. I'd say it's just a tremec problem. Something a little out of tolerance.

 

DAMN!! How hard, or forcing of gear change would that take! I replaced lower unit w/after-market shifter & was amazed at how crappy/cheap GM (or vendor) made them, especially the cup the bottom of the shifter sits in. Looked like a Reeses peanut butter cup wrapper.

 

Younger motocross rider, going hard is probably a force of habit.

 

Yea I am not smashing the gears or really pushing it hard. Going into 3rd or 4th is incredibly smooth. But if I go from 1 to 2, it can feel the notches. And I know it's in gear after the 2nd notch. But on downshifts it can take outright force to get it into 2nd and 1st. If I sit at the traffic light and go back and forth between 1 and 2 it becomes smooth. No clue what to do about it but it's annoying when the other gears feel perfect.

 

Same here. And the same with my ATS-V. It is typical of this transmission.

 

Typical of all these transmissions.

First, NEVER make a quick 1-2 upshift until the drivetrain is fully "warmed up." Even then, never "throw" or force the 1-2 upshifts. Accept this operational limitation and you will likely never have any additional or worsening problems. A very, very slight pause while placing a very slight pressure against the synchro gate just before actually pulling it through the gate virtually eliminates all these problems and prevents them from worsening.

Second, always double clutch or at least "blip" the throttle when downshifting these trannys.

 

+1 it doesn't have to happen if you take care of it.

 

Any of these other fluids go against the factory OR extended warranty?

 

I owned a 2014 from almost new, it would grind going into 2nd gear 70% of the time. These are easy shifts, been driving corvettes since 1970. I changed the fluid to Red Line, talked to GM “engineers” when they called me! Not the other way around! I was told when they added the 7th gear to get better mileage, the synchro was shortened up to allow it to fit. Whatever, it was unbearable. I sold the car a year later. Other then the shifter grind it was a fantastic car. Pity, GM never admits they fucked up.

 

Any manual transmission will over time develop a hard shift or grind or crunch into 2nd gear. What happens is no matter how careful you shift, you sometimes miss a perfect shift by a small amount and the synchro's will grind their tips down. They are no longer pointed but flattened or squared off. When you have grinded them down enough shifts become hard and chunky and crunchy Only solution is to replace syncs.
Replaced many over the years. Thats why I finally moved to an automatic.

 

Well I might agree with you except for a couple of things. This 2014 I owned had only 300 miles on it when I noticed it. Lots of other 7 speed owners have complained of this, and of course GM denies it. I also owned several C-6’s with the Tremec 6 speed and had zero issues, shifted like silk, even better with RedLine oil. It’s true 2nd gear synchro is the first to give you trouble wether a Munci, Tremec, Ford, whatever. However driving carefully, using an upgraded synthetic tranny oil you should have no problems period.

 

You can destroy a 2nd gear synchro in less than 100 miles if you don't know what you are doing or are very unlucky on your shifts. ( grind, crunch, pops out of gear etc... UUUgh ! )
Syncros are made of a very soft material compared to the rest of the tranny. Thats why they work and fail.