lars

In a post by “hderr” almost a year ago, Hank was having trouble getting his ’62 clutch to fully disengage. A lot of people offered a lot of advice, but the problem was never resolved:
https://www.corvetteforum.com/forums...ease-62-a.html

On a similar note, I have found that the problem with the clutch not fully disengaging is a very common issue on Corvettes. I posted the following article here on the Forum dealing with this subject:
https://www.corvetteforum.com/forums...vel-range.html

So Hank trailered his ’62 in from out-of-State this afternoon and dropped it off with me. I’ll be posting up a photo essay in this thread of the work, from pulling the tranny, inspecting the parts, determining clutch disengagement characteristics, and putting it all back together to create a nice running, reliable clutch system. Follow along as we disassemble the parts, test them, and find the problems. This will be an ongoing thread until the car is fully assembled and back on the road over a period of a couple of weeks.

Here's Hank dropping off his super-nice '62 after the road trip:




Car is stashed under the '66 Vette with the harmonic balancer failure from this post:
https://www.corvetteforum.com/forums...blem-post.html
The new balancer for Mark's '66 will be delivered in the morning, so watch for the completion of that project with test drive results...


Once Mark's car is off the lift, we'll get Hank's '62 up in the air for disassembly:


The bar is always open to anyone stopping by to view projects in work in the Corvette Viking Lounge & Workshop. "The Corvette Viking Lounge - a short enjoyable drive from anywhere":


Photos and write-up to come as we pull the tranny and disassemble the clutch system for evaluation...


Lars

GTR1999

I'm looking forward to these two Lars. I wouldn't mind having either one, the 66 looks sharp with the wheels and hardtop.

How tall is your ceiling, I was trying to gage it.

Bluestripe67

These documented projects are great for the forum and show the talent of our members. Thanks Lars Dennis

lars

Hi Gary!
The '66 is a 350 horse 327 L79, so it should run real nice after fixing the balancer problem and giving it a quick tune - I'm hoping to have it running better than Mark has ever had it running... Hank's '62 also sounds like it has some real potential as a fun driver, so I'm looking forward to setting it up right once I figure out the clutch problems...

I have 12-foot ceilings. That's tall enough to do Corvette and GTO work, but not tall enough to do minivan and truck work. That gets me out of doing any of that work for "friends" and neighbors.... (If you don't have any friends, just put a lift in your garage. "Friends" will never stop coming by.)

Thanks for the nice comments, Dennis. It's the people who appreciate the tech info that encourage me to keep this stuff going - it's fun to do nice work for good people.

Lars

Sky65

Thanks Lars. I learn something every time you post. Look forward to seeing what you find.

Tom

Avispa

Lars, that's time out of your day spent helping the rest of us. Thank you.

lars

The clutch project is underway!

As with any major work, the first order of business is to disconnect the battery... the starter will need to be unbolted in order to remove the bellhousing (the starter was attached to the bellhousing in 1962 - not bolted to the engine block), and we don't want to make any sparks doing that:


The clutch rod is then disconnected from the clutch fork:


...and the big, heavy return & over-center spring is then disconnected from the clutch bellcrank (aka, "Z-Bar"). The C1 Vette uses a super-heavy return spring that would go over-center to add force to the clutch pedal effort, making the clutch seem lighter than it really was. Rather than attaching the Z-Bar pivot ball to the engine block, as was done on the C2/C3 cars, the C1 attached the pivot ball to a bracket bolted to the bellhousing. So the return spring must be disconnected prior to removing the Z-Bar attach ball bracket on the bellhousing:


The C1's have a standard-type driveshaft, and the yoke must be removed out of the transmission, unlike C2/C3 where the driveshaft can be unbolted from the tranny yoke. So the driveshaft is unbolted at the differential, and the driveshaft is slid out of the tranny:


Driveshaft coming out:


This leaves a big open hole in the back of the tranny, which will spill gear oil all over your floor....


To prevent this, I use a spare yoke like this to stick into the tranny prior to removal:


Yoke installed, tranny plugged, and ready for removal:


The C1 Vettes have a small, removable tranny crossmember, which makes transmission removal much easier than the C2/C3 cars with the non-removable crossmember. The bolts are simply removed from the crossmember:


...the transmission is supported and raised up off the crossmember:


...and the crossmember is removed:


With the crossmember out of the way, the shift linkage can be removed. I like to unbolt the levers from the transmission to get it all out of the way. Note that the 1-2 and 3-4 levers go "up," while the reverse lever goes "down":


Shift linkage hanging free, and speedo cable removed from the transmission:


The 2 bolts holding the Hurst shifter to the transmission can then be easily loosened, and with the shifter ball removed from the shifter, the entire shifter with linkage attached drops right out the bottom of the car:


The 4 bolts holding the tranny to the bellhousing can now be removed:


The tranny then slides back until the input shaft clears the bellhousing:


...and drops clear out of the car. The C2/C3 transmissions cannot be removed this easily, because they cannot be slid back far enough for the input shaft to come clear of the bellhousing. In C2/C3 cars with non-removable crossmembers, the tranny must be unbolted from the bellhousing, and then the bellhousing must be unbolted from the engine. The tranny and bellhousing must then be "jack-knifed" out of the car together. But the C1 will drop clean - tranny is out and on the tranny jack:


After removing the throwout bearing from the clutch fork, a quick inspection shows that the geometry of the clutch fork is way off: In the "pedal up" position, the "face" of the clutch fork holding the bearing should be flat and perpendicular to the centerline of the vehicle. Here, a very long clutch fork rod has been installed, adjusted to the end of its adjustment, putting the clutch fork at a significant angle before the clutch is ever depressed. This can be caused by any combination of the following: Wrong throwout bearing length; wrong clutch fork pivot ball height; or wrong/defective pressure plate:


The bellhousing-mounted starter can now be unbolted from the bellhousing. The starter is not removed from the vehicle - it just rests in place after being unbolted:


The bellhousing can now be easily unbolted using a swivel socket:


Bellhousing coming out:


Ready for pressure plate and clutch removal, and things aren't looking right....


Flywheel is badly heat scored, but only on 1/3 of the swept area... Hmmmm...


Pressure plate is also burned:


With the flywheel removed from the engine, the flywheel, clutch and pressure plate are re-assembled on the bench to check things out. Confirming that "something didn't look right" in the photo above, notice that one of the 3 clutch fingers is depressed far lower than the other 2. This explains why the heat burning/discoloration is only on 1/3 of the pressure plate disc circumference:




The throwout bearing should sit flat and level across all 3 fingers:


Typical "exact reproduction" pressure plate and clutch being sold by many of the "restoration" parts houses - watch out for this stuff...


With all the parts out of the car, the clutch linkage is then re-installed with the Z-Bar, return spring, bellhousing, clutch fork rod, and the clutch fork. It is imperative to check and verify that the car itself has adequate clutch linkage travel to fully disengage a correctly-spec'ed pressure plate. A correctly-operating pressure plate will achieve full clutch disc release (defined as .050" of clearance between the clutch disc and the pressure plate surface) at .480" of throwout bearing movement. So the linkage in the vehicle must be capable of moving the throwout bearing through at least 1/2" of travel. If the throwout bearing can't move a full 1/2", no clutch system is ever going to work correctly.

So with a helper in the car to depress the clutch pedal, a bubble-level was clamped to the forward surface of the clutch fork (to assure that it was measured in the same vertical position in both "pedal up" and "pedal down" positions). A steel scale was clamped across the tranny hole in the bellhousing to provide a datum surface for the measurements. In the "pedal up" position, the throwout bearing mounting surface on the fork was 1.10" from the surface of the scale. With the clutch pedal fully depressed, the measurement was 1.70". This means that the clutch linkage in the car has a travel range capability of .600", which is more than enough to make a good clutch work correctly.


So what does all this mean? We have discovered several facts:

• The clutch linkage in the car is operating correctly, and will function right with a good clutch.
• The clutch fork pivot ball is incorrect (too short), and is causing the wrong geometry for the throwout bearing fork.
• The pressure plate is defective.
• All friction surfaces are burned, and the flywheel will need to be turned.

Now it's time to order some good parts, do a little machine work, and then put this together correctly with the right parts set up the right way.... The assembly and setup process, along with testing of the new parts to verify disengagement specs prior to assembly, coming up as soon as the parts arrive...


Lars

Jebbysan

lars

Jebby -
...isn't that a radio brand...? This is a clutch article.... geeez... you Texans...

Jebbysan

lars

This thread/post consolidated and pulled together in a single post here:

https://www.corvetteforum.com/forums...-c1-vette.html

This thread/post now discontinued in the interest of the new, continuous thread. Thanks!

Lars

CaptainEgg

Did I miss something? How was the back of the engine held up to remove tranny?

lars

Please note that the post has been moved to:
ttps://www.corvetteforum.com/forums...-c1-vette.html

There is no need to support the back of the engine - it stays right where it is. It tilts down just a tad when the tranny crossmember is removed - just enough to get easy access to the bellhousing bolts.

Lars