OH GOD I LOVE THIS ANSWER! This is just the kind of stuff that causes problems like this that crop up recently and mysteriously. Try removing the accessory belts (alternator, p/s pump, a/c compressor, waterpump), one at a time if possible and see if this changes anything. Maybe remove the fan and fan clutch and see if it makes any difference. Inspect the blade and clutch closely while you've got them off. Check the fan clutch mounting flange on the water pump and the pump impeller shaft. STAY CLEAR OF THE FRONT OF THE ENGINE AND FAN AREA IF YOU'RE REVVING IT WITH EVERYTHING STILL HOOKED UP! If the fan blade fails, you don't want to be in the neighborhood when it happens!
""prolly the flexplate or sumthin"...which doesn't tell me enough to go tearing my truck apart" Taking the 3 (or 4) bolts out of the converter isn;t tearing your truck apart,,it's eliminating any issues behind the flexplate,plus you should be able to better see if theres any rust around the flexplate to crank flange as mentioned. Also,,With the converter slide back,you could also take a fairly long screwdriver & "flex" the flexplate in various spots & see if something doesn't 'feel' right. Good luck
Twice in a lifetime at least, I've had it happen to me too....of course it WASN'T an off topic camaro.... it was an off topic truck...
On the flexplate. As was recently explained to me. The 86 and up 1 piece main sbc is internally balanced. The dampener is neutral, the crank is neutral, the flywheel is weighted. WHY? The rear of the crank is now round for the one piece main. If it had the tab like the old 2 piece main cranks it would be a no go for the seal. Sooooo, the weighted flexplate takes the place of the old oblong chevy bob weight on the end of the 2 piece main cranks. I'm not sure if this is 100% correct but it sounds right to me.
I had a simular problem I thought it was the clutch letting go or the flywheel but no luck there then I thought it was the balancer wrong again. Its was the carberator seems the floats and needles and seats were all screwed up I learned the hard way a chevy might pull a house but it won't pull a stump. Mine would idle fine and at about 1500 shake like crazy then level out under a load. I hope this helps
x2...lost 1 blade on a fan,didnt even notice it was gone,shook like hell as soon as i gave it any gas!
...sorry I saw lawless asked you this. I had this problem in the 55 several years ago, a bent crank that ate up the main bearings was the problem, it started as a decrease in oil pressure at acceleration then lead to heavy vibration and knocking, check your oil it will be full of gold flakes.
Sounds like a bad torque convertor. The earlier lock up convertors were bad about vibrating after getting a few miles on them.
I'm thinking he's talking about noise---I'm suspecting the flexplate now and it sounds like the starter needs shimming along with the vibration----
Welcome to the HAMB.There is a lot of Guys and Gals with 350s on here and your trouble could have happened to anyone of us, Good Tec reading.
May have been mentioned already, but check your fan. I have had a VERY similiar problem with a vibration in my Impala that turned out to be the fan. Just try a cheapo flex fan.
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