Probably run a little rougher and the teeth on the flywheel that the starter engages wouldn't last as long... to me, that'd be a totally useless thing to do for a Jeep that is driven on the street.

 

Usually I think the ring gear is steel, as well as the area where the clutch disc meets the flywheel. Still, not really a point to it on a jeep.

 

I would think the lighter flywheel would cost you low end torque.

 

I don't know that I've heard of an aluminum flywheel but the Mustang boards talk about lightening your rotating mass (alum. driveshaft seems to be a favorite) for various reasons. None of those reasons are attractive to me in regard to my Jeep and I don't race my GT Stang so heavy seems fine.

Why do you ask? Are you replacing the flywheel?

 

When I worked at Saleen building motors, clients would sometimes want their engine with lightened flywheels. Yes, it spooled a little faster, but it definately cost you low end torque, almost a bog when first taking off and disengaging the clutch. When we ran the higher boost on the supercharger, it definately spooled up alot quicker. Was it worth it......not in my opinion.

 

I wouldn't do it in a Jeep, I would assume the rotating mass of a heavier flywheel would make it harder to kill the engine if you dip down in the rpms while offroad, which would be a good thing.

 

No not changing flywheel. Just wondering what the effect would be.........thanks all!

 

What would be the effect of changing a 4.0 flywheel to a alum one??

A little more noise in the transmission from the occillation of the engine rotating a lighter flywheel. The momentum of a heavier flywheel smooths the pulses from each piston firing.

Faster spool up?

Yes, but it's a Jeep.

Less service life?

Not really but you may slip the clutch more with a AL flywheel to avoid stalling the engine. The momentum of the heavier flywheel may aid engaging the clutch quickly with less slip. Depends on how quickly you adjust to the lighter weight.

Better mileage?

You'll never see the improvement, if any.

An aluminum/light weight flywheel would be one mod to the Jeep I would not do. A standard/heavy flywheel will aid in smooth engine peformance especially in low RPM situations. Less chance of a stall when crawling or getting out of a tight situation.

One of my concerns would be if a random misfire code would be set you went too light on the flywheel. To a performance car, I would definitely install a lightweight flywheel - but not too light.

 

Diet and exercise will help you loose the same amount of weight a fly wheel swap will do and you'll get the added bonus of looking great!

 

We're talking about rotating mass .. not lard sat behind the steering wheel

I used to do this years ago with smaller Ford engines back in the UK Replace stock flywheels with lighter ones from smaller engines. The effect is higher reving more responsive engines, but you lose the torque from the rotating weight. Definately not going to do anything on a Jeep except allow you to stall the engine way more often.