Detroit flywheel

Lighter flywheels shift faster. I think that it needs to be significantly lighter though.

 

makes sense, all that rotating mass takes away for those rpms to come down. Isnt it weird how when you are loaded heavy as hell, you can shift super smooth coming out of a red light on an incline. Then when you are unloaded, its a bear and you have to wait awhile to get it in gear. In those are the times i throw on my engine fan to slow the motor for shifts.

 

I'll tell you one thing about the lighter flywheel. It will be a hell of a lot easier to put in.

Glad to hear you're going to get your repair done.

Be careful with that clutch though. That is one heavy mofo.

 

Less rotating mass means less momentum going up grade.

 

Put a 14 liter dampner on your 12.7 for some extra rotating force.

 

Way back when, drag racers used to put a truck flywheel behind a small block to get their cars to launch harder, but they dumped the clutch between 6k and 8k rpm.

I don't think a lighter flywheel in a diesel powered truck is going to make much difference when it comes to momentous torque going up hills.
Matter of fact it should pull better with a lighter flywheel because of the reduction in rotating mass.
In drag racing it's said that removing 25 lbs of rotating mass is the same as reducing the car's weight by 100 lbs or adding 10 hp.
If the engine was spinning 6000 rpm, there might be an advantage to a heavy flywheel, but at 1600 or 1700 rpm, not so much.
Unless you like to like to launch your truck hard, foot on the floor and dump the clutch, a heavy flywheel may improve your 60 ft times by a tenth or two and break many things in the process.

A heavier bob weight, rotating mass, makes an engine more durable, rob's power, but last's longer.