|
What's Clattering?
I'm hearing a metal/metal clattering noise from the drive train. It's not constant but I've nailed down a few possibilities and will have to look into it this weekend or soon. It's not getting worrisome, but it's not normal. 1980 911SC
1. At about 3,000 RPM, it sounds like valve clatter. I adjusted the valves last November (9,000 miles ago) and thought I got it right, but it's possible that I have a few a bit loose. Checking this will require $30 for the gaskets and nylocks.
2. This 210,000 mile transmission has been "repaired" several times, never properly rebuilt. The PO tried to show his son how to speed shift without the clutch, and lost second and fifth gear at about the 100,000 mile mark. At 190,000 miles, I lost first and second gear. The offended parts were replaced, but the whole (915) transmission has never (to my knowledge) been properly overhauled. Does the 915 make clattering noises at some RPMs? When I lost first and second, I pulled it and replaced it after repair and it came back to me dry. I can't recall what trans oil I put in there, but it wasn't Swepco.
3. The 210,000 mile motor (to my knowledge) has never been cracked open. The motor has the chain tension upgrade and the pop-off valve done. Could I be hearing a warn timing chain assembly?
There is no clatter at start-up cold, and no clatter at idle when hot.
There is no clatter below 3,000 RPM.
There is no clatter above 3300 RPM.
I cruise whatever gear I'm in at about 3000 RPM so that is a constant engine speed.
There is no clatter when pulling with torque from 2K RPM through 5K shift
There is no clatter when using about 75% throttle and rowing through the gears that I can hear - but I'm running a cat bypass and a stainless muffler with an 84mm single exit, so the hard exhaust noise may be hiding the clatter.
I can use a hollow pipe and listen to the valve covers and the valve chain covers to try to locate the noise, but it's tough to replicate it with hand throttle.
Any ideas?
|