does it happen when you accelerate and then quit when you step on it harder? also does it kind of shake the steering column when it does that? if so it may be the same problem i was having. the torque converter was shuddering when it was locking or unlocking. it has to do with the friction properties of the fluid affecting the clutches in the torque converter. i changed my transmission fluid and filter and it helped some but i am going to flush the system today. when you just do a regular fluid change the old fluid remains in the torque converter and fluid cooler. i am installing a aux. transmission cooler today and in the process i am going to flush out all of the old fluid.
hope this helps.

 

sounds like the trans, does it do it in 2nd

 

Thanks for the feedback. I just had the tranny rebuilt with new torque converter and auxillary cooler installed.
Put a new module in the distributor and it didn't help.

It is back at the tranny shop. They are going to pull the inspection panel and check for cracked flywheel and or loose torque converter. If that is not it, I am afraid it could be a bottom end knock.

Truck only has just over 100,000 miles on it and the motor was freshened up with flat top pistons and cam at 60,000 miles. The bottom end should be fine but who knows.

It does it in all gears. Seems to lessen at higher rpm.
If you load up the motor with your foot on the brake, its pretty loud at 1500 rpm.

I am definately leaning towards mechanical know versue electrical.

Just sounds like more money for the money pit. I'll let ya know. Thanks again.

 

well, it does it under high torque, ??? is it a sound that your worred about or sputtering in the engine (lack of power or anything)?

 

Well, I had the flywheel inspected for cracks at the tranny shop who built the tranny and it looks like the noise is coming from the bottom end of the motor as they had put a stethascope on it.

Started pulling the oil pan to look and figured screw it.
Decided to pull the motor. I should know on Thursday what is up with this money pit. Thanks guys for the feedback.

 

that sux. my vote: spun main bearing. that's what mine had. when the truck would be under a load and at operating temp, like cruising down the highway, itd sound like there was something flapping on the fan, but the noise wasn't up front. it was right underneath where the tranny and engine meet

after i'd let the truck stop and sit for a minute or three, it'd drive quiet and normal again. it was a royal PITA, i couldn't go anywhere on the hwy

but $3200 later, its all good

 

Ya, I am thinking spun bearing too. Not impressed as a 350 should not spin a bearing at 100,000 miles. I have friends that have triple that on a 305.

Should have it out and apart tomorrow.

Anyone heard of those oil coolers having a gasket tear out of them and getting into the oil pump causing it to take out the bottom end. Apparently it has happened to a few motors around here. Anyway mine is coming off. If I find this is what happened I'm sending letters to GM. Won't get me anywhere but at least I can vent.

Thanks for the feedback.