Contour Enthusiasts Group Archives Forums Modifications Transaxle quick question about "gear rollover noise"

Apparently it has been diagnosed that when a contour under goes a tranny overhaul including a "lighter flywheel such as Fidanza"
and a Spec clutch Stage 2 to be specific, the tranny then creates "Gear rollover noise" and some say clutch chatter.

I would appreciate it if someone would enlighten me and tell me what two moving parts inside the tranny create this noise. in other words what is the "origin" of this noise.?

Is it because it is a Spec Stg 2?
Because less rotating mass of the flywheel?
Perhaps alignment of the Focus shiftower?

Do all of you who had the Fidanza put in have this problem as well? or with both the Fidanza/ Spec Clutch?


Also when feathering the clutch, when the car is cold or has been parked for a bit , it makes a groaning noise, any ideas?

Thank You

Pressure plate fingers. The SPEC uses a custom, higher psi PP.

A lighter flywheel magnifies the effect.

From my understanding there are two seperate things that could be going on, either clutch chatter or gear roll over.

Gear rollover is rattling in the transmission, IIRC noticable when the car is in neutral and foot is off the clutch. With less mass on the flywheel there are more torsional vibes goin into the tranny and you can hear more rattling from the gears.

http://www.mts.com/nvd/pdf/GearRattle.PDF

Clutch chatter or groaning I think is more common with the clutch pedal pressed (ie clutch disengaged) or during clutch engagement. I think it is typical with more aggressive clutch materials and clutches with unsprung hubs. Google for clutch chatter and you 'll get lots of results like

Quote:

---

What could cause clutch chatter?
Chatter is when the car shudders as the clutch is being engaged. Possible [causes] may be as follows:

Flywheel has excessive run-out.
Flywheel was not resurfaced or improperly resurfaced before the new clutch was installed.
Damaged or excessively worn CV joints.
Bad U-joints in driveshaft or U-joints misaligned.
Excessive backlash in differential.
Excessive driveline angle.
Bad leaf springs, bushings or mounts.
The use of an aggressive clutch disc designed for racing.
Defective pressure plate and/or disc.
Disc has inadequate marcel (not enough cushion between the friction facing).
Oil or grease contamination on clutch facings.
Worn or damaged clutch linkage.
Bent pressure plate assembly and/or disc.
Improperly tuned engine.
Worn or damaged engine mounts or transmission mounts.

---

So, combine an unsprung heavy biting clutch with a very light flywheel and you will very likely get a rattling, chattery groaning setup that kicks ass performancewise

Gear roll over noise comes from the transmission itself. It is not a malfunction, it is a design compromise. It is the noise of the gears meshing as they turn inside the transmission. When designing the transmission, the noise can be eliminated or reduced by using finer teeth. The finer teeth are not as strong. So a given size transmission can be made stronger by using courser teeth but that also encourages noise. Of course a larger transmission could also be used, but it would be heavier.

Back in the days of the big block Corvettes, there was a transmission option known as the M-22. It was a stronger transmission ment for use behind mega power 427 cubic inch engines. It had the nick name of "rock crusher" because of the gear roll over noise that it generated.

Ligher flywheels seem to agrivate the noise. The noise tends to get worse as the clutch wears so it is usually less pronounced with a new clutch.

Our MTX-75 does indeed have some native gear roll over noise. It gets more noticable as the clutch wears. It tends to be a little more pronounced in the SVT, probably from the lighter flywheel. It doesn't hurt anything, it is just there.

A mod should sticky this, excellent info and its asked often.