Kozzzz

'12 Grand Sport with M6 trans, when the car is 'cold' there's a harsh grinding/grabbing sensation through the shifter when shifting from 1-2. It only happens the first minute or two of operation, once things warm up a little bit all shifting is smooth. If I shift from 1st, put it in neutral, and then shift to 2nd around a second later, I don't have that sensation when everything is 'cold'. Any ideas what the issue could be? Synchro? (Could a bad synchro get better with temperature?). I'll take it to a dealer later this year since it's still under warranty; but it's done this ever since I bought the car (used with 7500 miles), so I'm concerned it could be from abuse from the previous owner, in which case it might not be covered.

Garibaldi

Going by my experience with a 2011 GS and many responses on CF, what you're experiencing is normal: starting out cold, the M6 is a little crunchy going into second. You have to granny shift it. After it warms up a little, it gets better. Even when thoroughly warmed up, it's still a little notchy into second gear.

Boomer111

Normal should be better when warm.

Not really a grinding but more of a notchiness.

A real gear grinding, not meshing could be another problem but I am betting you have the normal notchiness going from 1-2 gear.

Pitufina

Change the fluid to Red Line DT4 and dont look back.

Boomer111

I use the Red Line oil in the trans and diff. Amsoil in the engine.

cclive

Very common issue...considered normal.

Kozzzz

I'm not sure if this is what I'd consider a 'notchy' feel. The shifter doesn't have any issue getting into the correct position, but the engagement feels bad. It feels and sounds like what I'd imagine it'd sound like if a gear was trying to mesh with a gear that's already spinning, it feels/sounds like the teeth of one gear are clattering off the tips of the teeth on the other gear a couple times before engaging. Granted, I can't see what's actually happening, but the feel and sound of it makes me visualize something like that in my head. Is that what you guys all experience too?

timd38

That is all I use and have since I got the car new in 2006.

AORoads

The usual response of normal is almost always correct especially due to design (but there was some redesign to trans synchro materials I think in your car's year). But it could be other things, too You are familiar with CAGS lockout at low rpm/speed, right? It can also be synchro, bad fluid (unlikely), possible shifter issues, and (unlikely) prior user abuse.

cclive

Don't worry about possible abuse from the previous owner...it is unlikely this but also undetectable by the dealership even if it was abused. I would bet that with few miles and possible babying by the previous owner, it is more likely a break-in issue rather than the opposite.

MyLS1Hauls

Thats not abnormal, and is quite common with the T56 and TR6060. Every one I've ever driven has done this a little when cold. The carbon fiber blocking ring for 2nd gear was supposed to resolve this issue in 2011, but I've heard rumors of some 2012 transmissions being disassembled, and finding the old style in there.

I like Royal Purple Synchromax in the trans (and I'm not a RP fanboy). It is a GL4 gear oil, rather than an ATF, but is still VERY thin. Lighter than SAE 30 motor oil. Shifts are definitely smoother than with DEX III.

SUB VETTE

You will be glad you did

Racer86

All modern manual transmissions have "constant mesh gears". The sound you hear is the teeth on the blocking ring and the synchro hub,. Each gear is always in contact with its corresponding gear. When you move the gear shift lever, you are moving the synchro hub teeth onto the blocking ring teeth, which is what locks the gear onto the shaft.

Bill Dearborn

There is nothing wrong. Once you drive a mile or so and the trans fluid warms up the notchiness and grabbing go away. Until it warms up you just need to shift slowly to avoid the feeling.

Bill

Garibaldi

When my GS is dead cold, I frequently shift from first to third, avoiding second altogether for the first couple of shifts.

Sayfoo

Document it with the dealer. You may even get a free fluid change.
I tried a aftermarket fluid in my '08 and didn't see any change. I then changed to the current GM recommended fluid, and it got a little better. If you have a '12, you probably have the newest recommended fluid.
Shifting technique can help alot. Try shifting at different rpms. Shift 1-neutral-2. Shift 1 to 3, etc.
52k miles here and it's not getting any better or worse, just a minor agravation.

Kozzzz

Thanks for the input guys! I feel better that there's no actual problem (I had some concerns about the car's previous history since it was bought back by GM from the original owner, and the engine was replaced under warranty prior to me buying it, so I was wondering if maybe there was some abuse or something in the past).

Any ideas why it only behaves that way when 'cold' (is it even due to temperature?)? Mine usually only does it for the 1st 1-2 shift. It might last for 2 1-2 shifts at the most before it seems to engage smoothly.

AORoads

The first part of the above post identifies your concerns re potential, prior=owner abuse. But, as stated by you and others, if it's ONLY for the first 1-2 shifts, it is most likely the fluid warming up and providing the needed lube. That's my guess. And I wouldn't worry about it.