Lets play guess the noise

[1985K10]

My 85K10 started making a strange noise about a month ago. When I'm cruising and have enough throttle to maintain my speed, and any speed, I get a kind of rattling noise, it goes away when I let off the throttle, or when I accelerate. But when I try to stay at one speed it does it. Its definitly coming from the engine or the tranny. Sounds like its between the back of the motor and the front of the tranny, which makes me think its the distributor, or the torque converter.

Extra info-Theres also a lifter that ticks untill the engine reaches like 160 deg, my engine is a 350(87 or up cuz the centerbolt valve covers),w/new Eddy carb, stock intake, HEI, the tranny is a 700R4 out of a 84K10(and the T/C), and was originally from a 84 Blazer. My lockup is working Just fine, well, it locks up in second gear, O/D works fine, the noise occurs in and out of O/D. Everything works fine, the truck drives fine, tranny feels smooth.

It almost sounds like its a couple metal plates clanking together. So my guess is the clutch in the lockup T/C.

[1987SierraClassic]

It could be the flexplate on the converter. My brother had one that was cracked and it took out chunks of the bellhousing when it blew apart thus junking the tranny...(Ford C6 in his case). Those driveline noises are tough to diagnose...I spent $700 rebuilding my transfer case only to find out the noise was from a wheel bearing! Run the truck on a lift (carefully) and have someone with a good ear listen as you try to duplicate the noise....

[Staceydude]

My first guess is timing is off and you are pinging.


Does it go away when you accelerate?

You said it goes away when you let off the gas.

Of course I may be way off base but thats my guess without being able to hear the noise.

Regards,

Stacey

[1985K10]

Well it goes away under hard acceleration. Now that I remember, i was bored one night so I checked the timing....the base was off about 8deg. It was at 0BTDC, and my book said it should be 8degBTDC. So I changed it, and I think thats when the problem started...........I dont know how i missed that...I'll back it off to what it was before and see if the noise goes away.

[jimfulco]

If it's pinging, you may have a non-functional EGR system. If the valve is disconnected or not opening properly, it will ping at part-throttle due to a too-lean mixture.

[1985K10]

I'll check the EGR too, thanks.

[1985K10]

I reset the timing back to or close to what it originally was and the "rattling" went away.

Now I have to deal with the front wheel bearings......