G6 transmission

The Dark Side of Will · Tue Jun 26, 2007 11:08 am

Let me check my notes on what the various parts of it cost. You buy the disks & floaters separate from the pressure plate.
I had designed a custom flywheel button as well as throw out bearing holder for it.

The Tilton is actually not too expensive when you consider that a SPEC stage III w/ lightweight option+ aluminum flywheel + throw out bearing comes to ~$800 and still hase MUCH greater MOI than the Tilton.

Series8217 · Post by **Series8217** » Tue Jun 26, 2007 2:59 pm

Eh, it's less than that.. ~$650. Flywheel $300 (ebay), Stage III $280 shipped (ultrarev.com), $79 lightweight option, and the TOB is included with all the Spec clutches; just need to make sure you order the one for the right transmission application and not just for the car/engine.
It will end up costing a lot more to get the Tilton setup to work.. and the Spec at least has a chance of still being driveable in traffic.

The Dark Side of Will · Tue Jun 26, 2007 3:28 pm

I was using SPEC's MSRP to compare apples to apples when I get Tilton's numbers from my notes tonight. You will NOT find a Tilton pressure plate appropriate to the Fiero used.

Like I said, I have the designs for the flywheel button and TOB holder... I'll have info on how hard those are to actually make after I make some.

The TOB holder can mostly be made on a lathe with just two mill cuts.

The flywheel can be cut from plate, then turned on a lathe. The labor inherent in that is cutting the center out of a flexplate to weld the rest of the flexplate to the flywheel.

Kohburn · Post by **Kohburn** » Tue Jun 26, 2007 3:37 pm

The Dark Side of Will wrote: The labor inherent in that is cutting the center out of a flexplate to weld the rest of the flexplate to the flywheel.

you mean like buying a new ring gear to weld onto the new flywheel?

Boscolingus · Post by **Boscolingus** » Tue Jun 26, 2007 9:11 pm

most flywheels I have had my hands on have the ring gear applied with a combination of heat and pressure - no welding. The only welding I have seen is on a flexplate.

Ok, mounts and brackets aside, where are we at with a break down of using this trans?

Axles? clutch/p.plate/flywheel? any clearance issues regarding the linkage on the top of the trans to the chassis?

EBSB52 · Post by **EBSB52** » Tue Jun 26, 2007 9:13 pm

Boscolingus wrote:most flywheels I have had my hands on have the ring gear applied with a combination of heat and pressure - no welding. The only welding I have seen is on a flexplate.

Ok, mounts and brackets aside, where are we at with a break down of using this trans?

Axles? clutch/p.plate/flywheel? any clearance issues regarding the linkage on the top of the trans to the chassis?

Ditto, what are the issues with this coupled to a N*?

The Dark Side of Will · Tue Jun 26, 2007 9:43 pm

Series8217 wrote:Eh, it's less than that.. ~$650. Flywheel $300 (ebay), Stage III $280 shipped (ultrarev.com), $79 lightweight option, and the TOB is included with all the Spec clutches; just need to make sure you order the one for the right transmission application and not just for the car/engine.
It will end up costing a lot more to get the Tilton setup to work.. and the Spec at least has a chance of still being driveable in traffic.

Numbers from Tilton:

Clutch cover (ultra-high ratio, 600 ftlbs)
66-302UORA (MSRP: $495)

25mmx14 disk pack Cerametallic
64185-7-AA-12 (12 = spline code) (MSRP: $260)

So the cost for the clutch itself is about the same as a SPEC/Flywheel setup. Yes, I'm still using new costs to compare apples to apples. I can pick up a Tilton clutch for $300 off ebay, but it won't be exactly what I want for this app.

The issues then are:
How easily can you fab or buy a flywheel?
How easily can you fab or buy a TOB adapter?
How easily can you modify the release mechanism to supply the higher force over shorter travel that the Tilton clutch requires?

Of these, it think the throw out mechanism will be the hardest because my way of dealing with it involves machining a new slave cylinder. I haven't decided what lengths I should go to in order to make this interchangeable with the stock unit.

Because the Tilton unit is 7.25" diameter, this will be the approximate diameter of the flywheel. In the absence of a good way to mount the starter closer to the crank, the ring gear has to remain the stock diameter. Since the extremity of the flexplate is no longer used to transmit torque, it can be whittled down to the minimum necessary to hold the ring gear against centrifugal force and welded on to the flywheel.

Kohburn · Post by **Kohburn** » Wed Jun 27, 2007 7:34 am

to get a higher force over shorter distance fromt he slave you can also just use a smaller diameter master cyl

dratts · Post by **dratts** » Wed Jun 27, 2007 9:19 am

Or a larger diameter slave cylinder!

Mach10 · Post by **Mach10** » Wed Jun 27, 2007 9:24 am

Wouldn't you be able to bore out the slave cylinder? Increase the diameter, and you increase the amount of force, while shortening the throw...

Going to a smaller master would increase pedal resistance, no?

Kohburn · Post by **Kohburn** » Wed Jun 27, 2007 9:43 am

you would on a transmission with a traditional slave and a throw out arm.
however isn't the g6 a hydraulic throw out bearing?

Kohburn · Post by **Kohburn** » Wed Jun 27, 2007 9:45 am

Mach10 wrote:Wouldn't you be able to bore out the slave cylinder? Increase the diameter, and you increase the amount of force, while shortening the throw...

Going to a smaller master would increase pedal resistance, no?

reducing the master or increasing the slave will both reduce the amount of fluid moved per inch of pedal travel. Thus increasing the force applied per inch of travel.

however he atleast implied that the tilton uses less travel - so it should balance out.

Mach10 · Post by **Mach10** » Wed Jun 27, 2007 10:11 am

I'm pretty sure I'm straight on this one;

Increasing the size of the slave means that your fluid is pushing on a larger surface; More VOLUME of fluid moving per inch of travel = More mechanical advantage.

Shrinking the master means more effort because you reduce the amount of fluid moving per inch of travel, with no increase in mechanical advantage; You're pushing against a smaller area, which means you need more pressure for a given output.

The Dark Side of Will · Wed Jun 27, 2007 11:01 am

Mach10 wrote:Wouldn't you be able to bore out the slave cylinder? Increase the diameter, and you increase the amount of force, while shortening the throw...

Going to a smaller master would increase pedal resistance, no?

No on both counts.
In order to use the full Fiero clutch pedal travel with the stock master cylinder to push the Tilton the appropriate distance, a slave cylinder diameter of a bit less than 2" is required. This results in a nice light 18# pedal load, though. The Tilton takes about .250 travel to disengage at its most worn.

Mach10 wrote:I'm pretty sure I'm straight on this one;

Increasing the size of the slave means that your fluid is pushing on a larger surface; More VOLUME of fluid moving per inch of travel = More mechanical advantage.

Correct.

Shrinking the master means more effort because you reduce the amount of fluid moving per inch of travel, with no increase in mechanical advantage; You're pushing against a smaller area, which means you need more pressure for a given output.

Not correct.
Think about it in terms of work. If you push 18# through 7" at the pedal, what force does that equate to for .250" of travel?
If you apply 18# of pedal force with a 4:1 pedal ratio, you're applying 72# of force to the MC. With a smaller MC, that force results in a higher pressure than with a larger MC. The higher pressure then creates for force at an equivalent slave cylinder. The smaller one moves less volume, so the slave doesn't move as far.

See this thread for the analysis: phpBB/viewtopic.php?t=3376

Mach10 · Post by **Mach10** » Wed Jun 27, 2007 11:36 am

My problem is that I'm thinking about it in terms of a lever; size doesn't matter, only the difference in size (moving the fulcrum)

The "input" (pedal throw) doesn't change, as it'll always be 7" correct?

So by moving the fulcrum over towards the load, you increase the mechanical advantage while reducing the amount of movement at the work end.

What flew over my head is that neither the fulcrum nor lever exist; and that the fluid is reversible; absolute size doesn't matter, just the relationship between the two. I.E., increasing the slave would have the same effect as shrinking the master.

I learn better this way. Thanks! :salute:

Series8217 · Post by **Series8217** » Wed Jun 27, 2007 9:38 pm

Wouldn't it be easiest to just use the biggest GM slave cylinder available, and make a new, longer release arm and a bracket for the slave?

Boscolingus · Post by **Boscolingus** » Wed Jun 27, 2007 10:20 pm

It would probably be something off of a C5500 with an NV5600 manual trans, OR off of a NV4500 5 speed manual early 90's with an external passenger side slave, not the internal slave on the late models.