Hi all, pretty much since I bought my '01 Z06 almost 1.5 years ago (@ 56k miles) it's been a little difficult to shift, especially reverse and 1st. Presently it's having problems with reverse "feeling" engaged and then grinding, or popping out of reverse. Also it happens often enough that 1st doesn't readily engage when the car is stopped.

There have been a number of things I've done attempting to alleviate this problem. This list is chronological:

• C6 upper shifter (better-looking ****, also in case my old shifter was worn. Used the pin to align it)
• TMOD Customs lower shifter box (frankly my old box didn't feel that sloppy. Unfortunately this lost the pin alignment feature)
• lightly used MGW C6 shifter with lower box (shorter throw, also tighter than stock C6 shifter. Made a replica of MGW's alignment tool and aligned shifter with that)
• Anti-venom mod with one washer (hoped it would reduce effort for reverse/5th/6th)
• Reverse lockout solenoid replaced (in case old one was sticking, causing difficulty accessing reverse)
• Reverse lockout solenoid spring replaced with a softer spring from Core Shifters (to reduce reverse gate effort)
• Transmission fluid drain/refill with Amsoil Torque Drive (in case old/bad fluid caused hard shifting)
• Katech remote clutch bleeder (to ease clutch fluid bleeding)
• Clutch system fluid bleed (to get out any air. Old fluid was pretty dark)
• Tick Master Cylinder installed, and adjusted to max throw where starter switch will still engage (also bled clutch system again)

As you can see it's a pretty long list... only things I haven't touched is the clutch itself.

Additional symptom: pretty regularly if the car is stopped, I depress the clutch pedal and put it in 1st, and the car "lurches" an inch. Almost as though the clutch is dragging enough and the transmission has to move just enough for first gear to engage.
This has led me to think the clutch simply isn't disengaging enough... clutch looked fine when the inspection cover was off, but I'm kicking myself for not having my wife press the pedal while I watch the clutch actuation.

These are the next steps I'm considering. The first two are nearly free, so fingers crossed on those:

1. play around with the fore/aft placement of the shift linkage on the shifter rod (I read this can make a difference)
2. again pull off the midpipe, tunnel plate, and clutch inspection cover. Mark the current SAC mechanism location and then reset it (in case the clutch drag is simply due to an over-adjusted SAC) BTW here is a guide which includes in-car SAC reset: https://paceperformance.com/files/pdf/zo6clutchadj.pdf
3. if SAC mechanism sets back to the same spot, strongly consider clutch/slave cylinder/torque tube job and all that is associated
4. do something with the transmission synchros while the trans is off???

Anyways, does anybody have any experience with my current scenario?
Thanks for reading!

 

What clutch, pressure plate and flywheel are you running?

 

To my knowledge it's the original clutch. Though I don't have any documentation proving so... but it was stock appearing at least.

 

I don't think that this is your problem, but I'll submit this comment. I had much the same issues much less severe and it turned out to be the pilot bearing.

 

usually with grinding or hard shift the synchros are the problem

 

Jmo friend had same issues. Replace clutch. Done. I mean when your in there replace all components that Relate to the clutch. Relax everybody jmo.

 

doubt it's the clutch itself because it's not slipping. hard shifts usually ends up being the synchros. Sometimes new fluid helps but he already ruled that out.

 

Thanks for sharing feedback guys.
I was hoping to get under the car today but that doesn't look promising. My in-laws want to come over for Easter (tomorrow) and it sounds like we will practice some form of social distancing in the garage... where the Z06 presently resides. (my other car is also down right now, so it's not moving)

You could very well be on to something. My other car, a 2001 Audi S4 6-speed, had what I believe may have been its original clutch and pilot bearing. I replaced all of that a little over a year ago. Pilot bearing was TOAST but it also had ~215k miles. That car would also lurch slightly when going into 1st... but my Z06 has only almost 70k miles. Though if it's all original the grease surely wore out a long time ago. Interestingly the S4 still lurches going into reverse despite new clutch/TO-bearing/pilot bearing.
https://photos.app.goo.gl/VMeaiETjH4pwdSdq5

Do worn synchros also result in the car lurching when going into gear with the clutch pedal fully depressed?

Definitely strongly considering it. But I'd like to minimize time spent working on the car unless I can be sure it's necessary. After all, I have a 10-week-old daughter, and as mentioned above a 2001 S4... that car is currently down because of a premature water pump failure (gotta do a full timing belt service to access it) and leaking cam and crank seals.

Right, clutch isn't slipping. But there is the potential for the opposite to be true... a clutch that doesn't fully disengage, due to a over-set SAC mechanism. Alternatively, other parts can be bad: pilot bearing, throwout bearing, slave cylinder.

 

your clutch isnt disengaging all the way. Disc could be worn or your slave could be leaking internally. Sounds like you know what to look for on the pilot bushing. Only one way to find out unfortunately

 

A real cheap try to rule out... noticed you have the TMOD shifter box, suggest pulling the console & see if the shifter box-to TT bolts are loose. When I did my tmod box, I didn't use locktite on the bolts like they said, & had shifting/grinding issues similar to what you're describing.

 

Well, I got under the car earlier today. Dropped the front end of the midpipes, enough to pull the clutch inspection cover.
Had my wife press the clutch pedal while I watched what was going on. My plan was to rotate the SAC mechanism into the "reset" position with the clutch disengaged, then release the pedal, and press the pedal again to see where it would reposition itself to.

Unfortunately I couldn't get the SAC plate to rotate at all. I was concerned about the possibility of breaking the tabs (adjacent to the SAC springs) if I pushed any harder. On the bright side the SAC didn't appear to be adjusted all the way out, but it could be frozen in place for all I know.

However, the clutch disk was definitely loose; even with the pedal only pressed maybe half-way I could spin the disk in place with ease (transmission in 1st gear). The clutch disk marcel springs also appeared to be working just fine. There was nothing obviously wrong with anything that I could see.

As mentioned above, the clutch disk at least is fully disengaging from the PP & FW. Slave was extending very far and wasn't retracting with consistent pedal pressure. Disk didn't appear excessively worn, nor does it exhibit any slipping.

Pilot bearing is a definite possibility. I mentioned in an earlier post that my 2001 S4's [original?] pilot bearing was toast, and as I recall it too had a slight lurching behavior in 1st gear prior to clutch replacement.

If you go back through my whole post (I know, it's long) you'll see that I have since replaced the C6/TMOD shifter with a full MGW shifter. The behavior didn't change. And all the bolts are tight.


When I came back into the house after buttoning everything up I told my wife that my next move with the car will be clutch replacement. Yay! This is turning out to be an expensive month between my S4's water pump failing (effectively necessitating a full timing belt job) and now planning a clutch job (with all that entails including torque tube rebuild) for the Z06. At least I do all my own work...

I already have a replacement slave cylinder (stock-style, got it for a great price) and now need to buy a clutch. Heavily leaning toward LS7 clutch kit due to price point and since this car is mostly a daily driver on more-or-less stock power.
Will also have to pick out torque tube rebuild bearings and couplers.

 

maybe this document will help: http://www.partinfo.co.uk/docs/141

The Corvette clutch is a diaphragm spring type pressure plate, much more complicated to troubleshoot than the old coil spring type us old geezers remember. It is easy to over match the hydraulic "throw" from the master to slave, and this is hard on the pressure plate diaphragm spring. Looking at the wear compensator diagram, it might be that over travel moves the wear compensator. There's nothing in the document that suggests that, though. You might also look at the tangential springs and see if they are bent. although that fact that the disc is free probably rules this out.

I think most if not all OEM clutches were LUK, at least the several I've swapped were. They are big in the OEM market, anyway, Usually with a Corvette, you find the pressure plate and flywheel have been overheated from poor driving habits. Other than that the biggest is clutch dust in the hydraulic system. Not much discussion about grenading, but there are people that could bust and anvil with a rubber hammer.

 

Thanks for sharing that document. Unfortunately I couldn't find anything relevant other than one spot where it mentions pilot bearing can cause the clutch to not disengage - though that was also previously mentioned here.
It's very possible there is overtravel and I need to reduce throw of the Tick Master Cylinder. BUT my current issue was present with all-stock hydraulics.

 

Well, things escalated quickly: I already have new FEBI torque tube couplers and SKF torque tube bearings. Today Fedex will be dropping off LUK LS7 clutch kit.

Looking for advice on replacing the rear main seal... for now there are zero oil leaks and in my other cars I've always skipped on the RMS during clutch jobs. BUT I'm contemplating the Sac City billet barbell, which necessitates rear cover removal. Should I just skip on both of those?

 

I’m going to go by memory here. The rear main cover is aligned by pins. So in theory, you could replace the main crank seal and it would remain concentric with the crank. I think the front seal is not pinned and hence the need to align if you remove the cover, and not needed if you just pop the seal, which is one b*$#h with the crank snout in the glide path for a removal tool.

Popping the whole BH is a chore, a couple of the bolts are easier to get to from the top with the intake removed. When you go back together, be very mindful of the wire bundle that can easily get pinched

 

Thanks for the input.
I'm actually looking at the whole cover replacement set (cover with seal installed and install tool, cover gasket, new bolts): Just ordered it, but doesn't mean I have to use it. Also it sounds like it's "good enough" to install this as-is without a separate tool (just the one it comes with) since the seal is already installed...

And I appreciate the advice on bell housing. On an old Audi A4 I had, I definitely pinched the starter wire harness between block and BH. That made for a fun first crank. Fortunately all was fine after adjusting the harness.

 

I don't know which is less of a pain, but you can also drop the engine cradle about an inch and remove the bolts that way from underneath. You might have to loosen the upper A-arms (I did) to get the engine to drop. You do not have to completely remove the 4 cradle bolts.

 

Thanks for the additional info Dutch08.

Yesterday the LUK LS7 clutch kit from RockAuto arrived. So far I have that, torque tube bearings, and torque tube rubber couplers. Also I have a Hinson polyurethane diff mount that I'm thinking to install.
Still waiting on the torque tube slinger, billet oil diverter barbell, and rear main seal + cover.
Also strongly considering ordering C6 Z06 diff clutch packs + belleville springs, and output shaft seals and side cover O-rings to refresh the LSD "while I'm in there". Have had some Mobil 1 LS diff fluid waiting to go in anyways. I think the bearings are all fine so don't have any plans to replace those...

 

FYI, I used Mobile 1 LS and after about 50 miles the diff sounded like it had sand it when turning. I switched back to GM AC Delco Diff fluid and a couple of figure 8's later it was perfect. In hindsight, I think I should have added friction modifier to the Mobile 1 and it probably would have been fine.

 

That seems really odd! Thanks for the heads up. If I run into the same scenario I could try adding friction modifier first, before swapping fluid.