I don't profess the 06 is light years ahead of an 07 just a little better to build from IMO....
My take on the crankshaft issues that began in 2007 are:
1. The crankpin was moved 3/16” further from the crankshaft center, increasing the stroke and the mechanical leverage of the flywheel’s inertia over the crankpin. This reduces the crankshaft’s capacity to resist high torsional load spikes.
2. The longer stroke results in increased mechanical leverage resulting in higher torsional loads throughout the powertrain.
3. The overall gear ratio changed substantially with the advent of the Cruise Drive to a numerically lower ratio. This change resulted in a substantial increase in load throughout the powertrain.
You have a scenario whereby the engine has increased capacity to produce high torsional loads; the crankshaft has reduced capacity to handle these loads and the drivetrain and chassis have less capacity to absorb and dampen these torsional load spikes. The engine makes more, and the rest of the powertrain and chassis absorb and dampen less.
The simple answer seems to be to build a stronger crankshaft, yet controlling the massive torsional load spikes created by this long stroke reciprocating engine is the answer, IMO. This is true with this powertrain as it is with any reciprocating, piston engine machine.
The answer to the question of what took care of the flywheel shift issues in ’08 and later machines, is the control of low RPM output and the increased dampening of the powertrain through use of an IDS and a high torque motor sprocket with 7x increased capacity.
....if you have a high torque motor you risk slipping a wheel (IDS or not) when rolling on in 6th unless the final drive ratio is lowered and/or the crank has been plugged or welded....
If powertrain loads increase and nothing is done do counter them, the likelihood that parts are going to break will increase. It appears that the IDS is adequate for a stock applications, but as the engine’s output increases, the capacity to dampen the increasing torsional loads must increase with it.
....The MOCO fixes of IDS, software, head gaskets made of Kevlar, blah blah blah
Band-aides IMO....
With respect to crankshaft “Band-aides”; if a 2007, 96” 6-speed, putting out 95 crankshaft foot pounds will generate torque spikes of 1,500ish + foot pounds at the crankpin, what kind of spikes would you expect to find with an engine putting out 140+ foot pounds at the rear wheel? Do you think that it is possible to make up that kind of difference by simply reinforcing the crankpin?
I have heard that the plugs are good for about 5% increase in capacity. If this is true they are certainly better than a poke in the eye; although I wouldn’t bet the farm on them.
If it is true that welding the crankpin compromises the interference fit in the flywheel, then it may be possible under certain circumstances to actually reduce the load capacity of this joint by welding it. With the interference fit compromised, it is likely that the joint will begin to flex, eventually resulting in the failure of the weld.
I believe that in time the answer for folks building high output Twin Cam’s will be not to focus on building a bigger anvil, but to dampen the forces of the hammer; although exactly when is hard to say. Mechanical devices have been used effectively to dampen torsional loads in reciprocating, piston engine powertrain’s for many decades.
As always, JMHO.
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Topic: Top end "clacking" sound (Read 56615 times)