The harmonics thing was an issue I looked into and heard a lot about it on the 6.5 forums. Mind you, I had timing gears custom made before for my racing mess years before. I found such AMAZINGLY contridictory info it was unbelievable. Once I realized that last statement, it hit me- some of it was unbelievable for a reason. It was amazingly false.
I didnt pull together all the info unfortunately or I would want to have a book Inplace of a thread. At the time there were a few prople that had different view points and people were hard dug into their stance.
In the end a few items that helped me decide. Flat out asking for pics and proof of longevity vs early death. Never did get a single picture showing early death. Stepping out of theoretical ip death on chevy’s vs long ip life on fords. Most chevy guys still think 150,000 miles is a good run on a db2. Ford guys get pissed off if the ip needs rebuilding just because the piston rings and valve seals are painting the hiway behind them. Hmm.
I had a few people contact me behind the scenes that pointed out parts sellers who only profit from selling chains were quick to point “faults” of gear drive, and gear drive resellers didn’t fight it back to often, if ever.
When the majority of the argument turns to harmonics into the ip through the out of balance set up becomes the biggest issue- it took me back to when my gears were custom made- and some of the guys helping with this crazy hot rod diesel idea back in the 90’s were big names in racing, so theory wasn’t theory- it was proven knowledge as fact.
We had the gears made a little lighter than dsg or Leroy’s current ones are. Basically narrowed in the middle. But even back then we talked about should we lighten it or make it heavier on purpose. The fact that it is slow rpm, small diameter, etc means lightening it doesn’t help that much. Cut weight in half at 4,000 rpm could mean a potential 0.25 hp. Yeah- big savings huh? So we had wide gear surface for applied load, knowing we were giving some up to drag, but still comparable to chain drag. Anyways the vibration issue was less concern because race engine vs daily driver. But the gears only transmit the vibrations so redoing my dd had me worried. Right?
If chain: Timing chain means gear only is cam vibration. So forget that. Your applied spring tension and valve smacking friction is the issue there, and until 5,500 rpm that doesn’t even record input.
Crankshaft is legitimate vibration. Assume gear drive And at specific harmonic rates can amplify. But the 2:1 ratio changes the rate by a factor down, not in half. So if your crank is out 12 grams, the gearing cut makes it 4 grams. But if your crankshaft really is out 12 grams, it will break in 3 months anyways- haha. Seriously thats like an unbalanced aftermarket crankshaft! So yeah, real engine death is a concern there. But to continue if you have your crank at factory horrible spec of 4 grams, one gram at the cam and ip is possible. Now this factor is affecting the alplitude of the vibration. The frequency will stay the same.
The chain slap is supposed to ease up the vibration and only stretch the chain faster. Makes sense. But why do pumps live longer on fords?
The vibration transfered in through the gear to the cam has so much less than the valve spring slamming up and down on the cam at all time cause their own vibration. Harmonic dampers were once made for camshafts for this issue but were abandoned because the advance and retard action of it was more counter productive than any vibration savings they made. Know what else has advance and retarding action? Timing chain slap and timing variations every time the engine goes
From deceleration to maintain or maintain to accelerate.
That got me to looking at which is more damaging slap vs crankshaft relayed vibration. Cams shatter so easy when you drop them- As hard as possible and as little deflection as possible by design. But carburetors and gasoline injectors dont need an ip. Vibration into a camshaft from the crank isn’t even thought of in most engines.
So if the number one vibration creater is valve chatter & springs to the cam aside from MAYBE the relayed crankshaft, and I was worried about vibration into the ip... the cam vibrations are still into the ip, regardless of timing chain being able to absorb the crankshaft issue the valvetrain created vibrations should be killing the ford ip- but it isn’t!
Rip apart any ip. Look at the worn out components. Rotational wear. Contamination causing scoring and erosion. Try, just try to find evidence of vibrations related wear in any ip. Show me how much worse it is in a gm vs a ford which if you didn’t already know or figure out by now, uses gear drive not a chain drive. Why does Ford? Same reson EVERY OTHER DIESEL mfr does. It works. Know how many big rig engines have a kazillion miles on them? Know how many of them use timing chains?
Why? Why the confusion / discussion on gm diesel boards?
Misinformation driven by profit market share is why. Do some people honestly believe the chain is better- I am sure there is some people that were convinced of it. It’s ok, errors can be corrected.