facs24dave

I have a 2005 6 Speed Base C6 with 60k miles. When shifting into second when cold it tends to grind every once in awhile, and when downshifting from 3rd to 2nd, or 2nd to 1st. It almost seems like the clutch isn't fully disengaging cause if I push it in and hold it for a second before downshifting, when i downshift before letting out it sounds as though the clutch is "spooling up". From some reading I got changing the fluids in tranny, and probably flushing the clutch and replacing fluids there may help, and if so, what should I switch to as far as fluids? Only had the car a month and am crossing my fingers it's an easy fix!

thanks in advance for any help!

Rick@RKT Performance

When you have transmission problems, try these before getting into the internals of the transmission itself.

1) Perform the shifter alignment.

2) Make sure the shifter base bolts or the shifter shaft bolt is tight.

3) Change the fluid (I recommend GM part # 88861800)

If all above doen't fix your problem, contact one of the forum sponsor trans builders.

facs24dave

not the news I was hoping for, but thanks for the information! any other ideas guys?

360jeepboy

That is good advice. Have you done everything Rick has said? If not then why not start there. New shifter base bushing might be in order.

vetdude

I'd try swapping out the trans fluid with a good synthetic, like Royal Purple. Flushing the clutch fluid and refilling with fresh wouldn't hurt either. Good luck!

SUB VETTE

see thread above "clutch/transmission problems by pratner

facs24dave

as in the pice located at the bottom of the shifter? New to the whole Corvette/Manual tranny setup. thanks!

breecher_7

What is this "shifter alignment" you speak of? The shifter only bolts into the box one way, didnt think anything could be "aligned"

My wifes 2010 is EXTREMELY notchy, almost grindy, into 2nd and 3rd gear when the trans is cold...

AORoads

only had it a month and 60K miles could also mean the prior owners were not so gentle on it. that aside, replace the fluids, trans and clutch reservoir and see if that helps.

but know this, too: seems like the T-56 and later model TR 6060 all are very notchy when cold---not just cold outside, but cold until the trans fluid itself warms up. and the gap from 1st to 2nd is usually a big change for the trans. there are several driving techniques to compensate for this, but they require your patience (such as double clutching, shifting slowly when the trans is cold, cutting out 2nd to 1st downshifts without letting out the clutch in neutral first, shifting 1 to 3 and bypassing second gear when cold, etc.) without doing that, you run the risk of damaging the synchros or the gears or both which is a big cost. a new clutch is expensive as it is w/o doing the damage to the trans itself.

SUB VETTE

There are two rubber bushings between the shifter box and the torque tube mount that it bolts to which over time deteriorate and allow the box to move around. The bolt holes in th shifter box are oblong and allow the box to be adjusted fore and aft. With the box bushings shot, the box can move fore and aft when you are shifting causing missed shifts etc. New bushings eliminate that problem.

SUB VETTE

The shifter bolts on to the box only one way - true. But the box mounts to the torque tube with oblong holes that allow fore and aft adjustment.

breecher_7

Aware of that, didnt know thats what they were referring to. They should all come with solid bushings, those rubber ones are nothing but trouble.

facs24dave

anyone you know of on the forum i could get them from? thanks!

AORoads

you could ask rick, post #2.

SUB VETTE

Mid America Motorworks (mamotorworks.com) stocks them for $19.99 (set of 4, only 2 needed) part #627-379.

Driver_WT

Here is an issue that I had to have fixed on my 05 C6

Document ID# 1690618


--------------------------------------------------------------------------------

Intermittent Block Out of First Gear from a Stop - keywords hard no shift shifter stop #PIP3513 - (Aug 5, 2005)
Intermittent Block Out of First Gear from a Stop
2005 Cadillac CTS-V

2005 Chevrolet Corvette and SSR

2005 Pontiac GTO

Equipped with Manual 6 Speed (RPO - MM6, M10, M12 or MZ6) Transmission

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
Intermittent block out of first gear at a stop. Driver may have the vehicle in neutral while stopped in traffic and when depressing the clutch pedal to engage first gear, the shift is blocked.

Recommendation/Instructions:
If this condition occurs less than 5 percent of the time, it would be considered normal. This condition occurring more than 5 percent of the time should be repaired. A clutching tooth improvement has been made to the first speed gear. Replace the first speed gear in the transmission. Check the gap between the vertical faces of the blocking ring teeth and the speed gear as per Document ID # 588712.

Transmission
Application
Part Number

MM6
Corvette
12455013

MZ6, M12
Corvette
88894089

M12
CTS-V
88894089

M12
GTO
88894089

M10
SSR
89059976


Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.



GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
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facs24dave

unfortunately soundsa about right, why cant they make it a recall and help us out a bit?

torquetube

It sounds like you're describing the sound of the motionless driveline between the clutch and the transmission being spun back up by the poor little gear synchronizer. If you wait a long time to shift after pressing the clutch pedal, that will inevitably have to happen.

I suspect your problems are due to technique that may have been masked earlier by fresher gearbox lube and warmer temperatures. I suggest 1) not downshifting to decelerate, which is what brakes are for; 2) rev-matching when downshifting for legitimate purposes; and 3) changing the transmission fluid - at 60K miles, it's about time.