excessive clatter at zero throttle

[gwaidman]

A friend at work has a 98 chev 3500 4x4 auto 6.5td and it suddenly started making very loud engine clatter when he was slowing down or at a stop, but the moment that you touch the throttle it goes away . The speedometer also jumps to about 5 or 6 when stopped. Took off the belt and still there. No shavings in the oil filter and lots of oil pressure. What could this be??

[BuffaloGuy]

Perhaps a wore out wrist pin. They are not under oil pressure (only by splash) so you wouldn't see a loss in oil pressure.

If you use a mechanics stethoscope you should be able to find the sound.

I hope I'm worng. It ain't cheap.
Ken

[ogrice]

Since your truck is a manual trans. The clatter can be your dual mass flywheel and clutch. If the clatter has just started, you want to buy the single mass flywheel and kevlar clutch upgrade before too long (available from Heath site). If you do not, the clatter is going to mess your the input shaft on your trans and you are going to have to replace gears soon.

If the noise also goes away or gets quieter when you depress the clutch, then take action. I didn't and I let the clatter go on for a long time. When it came time to replace the engine I did the trans too. The rebuild cost me 1600$. I had to replace the input shaft, the 1st gear, and overdrive gear clusters. If I didn't have to get all of those repairs, the trans rebuild would have been a managable 400$. For 1600$ I would have gotten a reman nv4500 trans on ebay with a warranty.

Keep troubleshooting till you find out. If it is the trans, then act quick. Spend the money now or spend it later.