The Spark

I tried asking this in the C5 Tech forum first but no answer yet.

I have a 99 Coupe with original clutch, shifter, etc. It has about 60,000 miles on the car but I've only tracked it about a year and a half now - HPDE and TT.

I am running trans and diff coolers and Royal Purple fluids.

I am having trouble from time to time with 4-3 and 3-2 downshifts.
It is not all the time and seems to be limited to just a few corners at each track. Seems weird but thinking about it seems to be worse when it is hard braking into a slow corner.

It will not go into lower gear or I have to really fight it to go into gear.

I have been having sticky-clutch-pedal syndrom even though I have tried changing clutch fuid with pump-refill method. Great fun pulling the clutch pedal back up with your foot!

I'm definitely not the best heel-toe driver but that doesn't seem to affect the shifting problems.

What do you think? Clutch? Synchros? Shifter?

I have had a little gear grinding when downshifting but it is very infrequent. No problems shifting up or down when on warm up or cool down laps.

It is really pissing me off. I was chasing down a Viper at the track and lost him when I blew shifts in two corners on one lap.

SIK02SS

my 2nd time out in my C5 i had a similar issue, i would downshift to 2nd and it would feel like it went in, then when releasing the clutch (brand new clutch) the gear lever would pop out and i would fight it to get in gear or it just wouldn't go at all. Finally discovered it was the shifter alignment, iirc, it kept sliding rear wards so we replaced the hardware (new bolts with lock washers) and haven't had an issue since..

hope this helps

CP Thunder

When you say 'fight it' do you mean 'manhandle' it to get it in gear? If you force the issue, you can easily bend the shift forks in the stock tranny.........if you ever have it rebuilt, make sure you ask for steel shift forks......

Ranger

Suggest three steps.

(1) Clean up the clutch fluid until it remains clear (not cloudy) after a 20 minute drive that includes a lot of up/down shifts below 3K rpm.

(2) Replace the clutch master cylinder. It probably is failing to hold nominal pressure under track conditions. MC is the cheapest clutch element and is accessible without dropping the drive train. Just requires removing LF wheel and opening the fender liner.

(3) Swap the tranny fluid, unless that's been done in the last 10K miles.

Ranger

VetteDrmr

Ranger kinda beat me to it, but it seems to me that it's happening when you're downshifting early into your braking area (i.e. high rpm downshifts), and that the clutch isn't disengaging completely. My first guess would be MC, since usually the slave problems have to do with sticking upon releasing pedal pressure.

HTH, and have a good one,
Mike

The Spark

It doesn't pop out of gear. It either goes in or it won't. I'll try replacing the hardware to make sure shifter isn't moving.

When I say fight it, I mean I pull/push harder than normal and it won't go in gear or it finally will. Good point on the forks. Thanks for reminding me. I get pissed when it won't go in gear and I start losing my temper.

I'll check out MC swap too Ranger. I've got some time before next track day. May not be a bad idea - just to take one more piece out of the puzzle.

The fluid was replaced in March when I installed the coolers.

wtknght1

I'm not sure if you have a racing seat and belts in the car or not, but your problem is most likely your shifting angle, and motion. You said it normally happens under heavy braking. Under heavy braking, your body will move slightly forward (as does your arm) which changes your shifting angle...and possible causes you to miss the gate.

There are other things in that too - clutch not being depressed all the way...or trying to release it too soon...mostly due to the fact that you've changed positions and are 'trying too hard.' Smooth out, relax and see how it goes. Work up your speed slowly really concentrating on hitting that shift and see how it goes.

One other thing that helped my transmissions shift better was fully warming it up. On my warm up lap, I shift thru every gear - twice...all the way to 6th just to make sure that all the synchros are warm and ready. I found that when I didn't do that, my 3-4 shift was not always on par.

Those are the cheap and easy things to do... If all that doesn't work, you may have a broken part or two under there...specifically the rear diff bolts. Both of my rear diff bolts were broken on my C5 for several events, but I didn't know it cause they are very hard to get to...and even see. Have a good mechanic do a "nut and bolt" on the car and check all of them for correct tightness...and ensure there's no play. I put a fairly scary video on You Tube showing what happens to the drive line when those bolts are broken! Yikes!

Good luck!

SIK02SS

i just remembered, not only was it popping out, but later i went to shift (up or down) into 2nd gear and periodically 4th gear and it was like it hit a wall, i would keep trying and then all of a sudden it slid right in. before you start buying things, I do suggest you remove your console (if you have to) or shift boot/**** and check the shifter to see if it has actually moved at all or has loose bolts. It could be as simple as this..

wtknght1

Oh, I almost forgot - The pressure plates on these vettes are really only good for about 2 years (of really hard driving) before the "teeth" start to break off. When they do, shifting becomes very difficult. You'll know when some teeth are broken when you shift into 1st gear and the car moves a little before you even let out the clutch.

John Shiels

syncros possibly

yakisoba

Yeah. Start getting set up for a trans/clutch job. If you're lucky, it's the MC. If not, you're looking at an RPM (or other) transmission, which is not a bad thing!

joemoia

My experience with the "stuck pedal syndrome" was that, when it occurred, I had difficulty completing the downshift, similar to what you described. The problem occured in specific corners when braking/down shifting from high RPM. If I was running behind other traffic at a slightly lower RPM it didn't occur. The problem started only AFTER I had replaced the original clutch/slave assy at 60K mi., and changing the clutch fluid proved ineffective. I ended up changing the clutch/slave a 2nd time.

Kanmer

I hate to say it but my first guess would be slave cylinder. Try the other things first but if they don't work, be prepared for a slave cylinder replacement. Thats a fun job!

Bob

Woods

I chased this issue for a full year and tried all the band aids, flush fluid, Clutch Master. But a new clutch, pressure plate, pilot bearing and slave fixed it. Not a hard job but takes a lot of time

Ranger

High-rpm upshifts and down-shifts produce big bursts of clutch dust that fouls the throwout bearing and covers the main-shaft on the actuator. Next push of the pedal and the O-ring on the main-shaft squeegees the dust into the clutch fluid. Left to accumulate, the dust shards (copper and iron) constitute an abrasive that destroys integrity of the hydraulic seals, particularly in the master cylinder.

The keys are:

(1) Preventative maintenance; frequent enough fluid swaps to avoid dust accumulation. That may include swaps between sessions.

(2) Don't have FWTQ that exceeds the clamping power of your clutch. If it does, the clutch slips under max load, producing prodigious volumes of clutch dust and heat that accelerate deterioration of the hydraulics. Once nominal hydraulic pressure cannot be met, the clutch fails to release and the pedal hangs. Tranny trashing often follows.

Ranger

ckolben

Apologies to the OP - don't mean to hijack but...

Can you explain this a little more? My car does exactly what you described when shifting into first gear with the pedal all the way to the floor. I've been wondering about the cause for months.

Ranger

I've consistently inspected my Corvette clutches once they have accumulated 150-175 drag strip passes. That includes measuring the height of the pressure plate finger compared to new. The five clutches I've examined have shown no notable change in the pressure plate configuration, other than the self-adjusting take-up mechanism working as designed. And the clamping power of the clutch remained quite constant throughout its life even when the clutch disc was quite worn and near end of life.

Movement of the car with the clutch pedal fully depressed in first gear, in my experience, is indicative of air in the clutch hydraulics causing an extremely low engagement point. That condition can normally be cleared by cleaning up the clutch fluid and disgorging trapped air by (1) following the protocol or (2) conventional bleed.

ckolben, What does your clutch fluid look like?

Ranger

wtknght1

Every time I have issues shifting, it's always been the pressure plate - specifically the little teeth in the middle of the plate. After about 2 years, those teeth begin breaking and you have those shifting issues I mentioned. It's never been anything else with my cars...ever. It's always been that damn plate. The clutches in these things are pretty much bullet-proof and so are the transmissions. My best advice is just have the pressure plate replaced and I'll bet $$ that your issues will disappear.

ckolben

ckolben, What does your clutch fluid look like?

Its clean, I change it often using your protocol.

I had a mechanical over-rev about a year ago and have been waiting for something to break loose as a result of that maneuver ever since. Reading about a potentially broken PP last night sounded plausible. Called Corvette Mike's today to get quotes on a clutch job. Described to shop tech what was going on and he suggested a look at hydraulic system not the clutch since I'm not getting any clutch slippage or vibration thru the pedal. I'm going to take it in and have them take a look-see.

NemesisC5

Like most clutch issues, several possibilities. I had rpm related issues that made up/down shifts difficult to execute, so I granny shifted for awhile. My clutch was beginning engagement 1" from the floor so I decided to install Mcleod MC first hoping for good results and in this case I was lucky & problem is gone. Now engagement begins about mid pedal & even 7k shifts are no drama. I was lucky to try this before removing drivetrain. Usually my luck/decisions cost me more money, more downtime and precious peace of mind.

Good Luck.