My Lightning has a weird chattering sound that almost sounds like valves out of adjustment or chattering lifters on a pushrod motor. I only does it above 3000 rpm in 3rd gear at a cruise. I thought it might be the bypass butterfly on the Eaton doing it, but I don't know. I have the bypass mod done... It did this before and after the 6lb lower pulley.

Sounds a lot like lifters pecking/chattering.

No, only when cruising in 3rd gear (no overdrive on) at around 3000+ rpm.

Don't like hearing it. It doesn't affect power, and when in overdrive, I cant hear it. Of course I am going pretty fast by then (3000rpm in overdrive). Also, under full throttle I don't hear anything. Sounds like it comes from the blower. Any ideas?

BTW, sometimes it sound's like an exhaust leak, but you don't hear it any other time.

 

No ideas?

 

You can't reproduce this when sitting still huh?

Is it a 1:1 ratio to the engine speed? 1/2 the engine speed? (Just trying to isolate that it's actually in the motor)

I'd sure think if it was motor related you could reproduce the same load with your foot on the brake and in 1st or 2nd gear.

If it's speed only related it could be exhaust, or some bearing within the drivetrain that's brinelled. Only showing up under light loads.

btw: I've heard of exhaust rattles showup only in these type of conditions.


Rich

 

It might be an exhaust rattle, because sometimes it sounds like that. I can't reproduce it sitting still (at least not lately). It definetly soundls like it is coming from under the hood. If it is exhaust, it only does it in these conditions whcih is weird. Any ideas where it might be coming from if it is the exhaust?

 

I had a belt idler that was chattering , but mostly at low speed when cold. But it is easy to check.

 

How did you check it? I don't mean to sound dumb, but it doesn't hurt to ask.

 

With the motor OFF.
reach in there and try to wiggle it. (there are at least 2)
If it has slop. It needs to be looked at\replaced .
You might also flex the tentioner and make sure it rolls freely.
Mine was loose on the driver side. Dealer replaced it.

 

Thanks!