So I finally got my 54 Bel Air running the other day, but since that time, I notice a knocking sound that I think is coming from the transmission. I only hear the knocking when the transmission is in gear and at idle. Once i get the RPM's up the knocking goes away. No knocking when its in idle and out of gear too. The transmission is a TH350 mated to a 235 inline 6 via a stovebolt adapter. The tranny was freshly rebuilt with a new low stall torque converter, flex plate, and starter. Any idea whats causing the knock???
Maybe the flax plate to crank bolts , or the converter bolts to flex plate maybe to long in no nut/bolt combo is being used. Had some thought were good flex plates crack at the crank bolts. Also some of the nuts welded to the converter were the thin style and standard bolts bottomed out & left just enough space to make the converter move. Hope this helps.
I once had the gear on my starter not retracting so it banged back & forth making a loud knocking sound. ... Check the easy stuff first
My first thought was loose convertor to flexplate bolts. I have seen people put up with that knock for a long time and then they found out a simple torquing of those bolts and nuts fixed the problem. Don
My friend put a brand new crate motor in his rod and drove 250 miles to a show. That last day he was there at the fairgrounds, he heard a knocking sound. Since he had bought the motor the year before from the GM reps at the show, he had them take a look. The reps couldn't figure it out so he trailered the car home. His son looked under the car and noticed the trans was separating from the block. Tightened up the trans bolts and the sound went away.
X2, had that happen on a 472 Cad with a turbo 400 trans. Used the stock converter to flex plate bolts, with a new converter. The bolts bottomed out and we thought they were tight. Installed new shorter bolts and the knock went away.
Converter bolt knock usually happens when the vehicle is at an idle in neutral and goes away when you put it in gear with a load on it. I'm thinking that Spiderville may have come the closest with the possibility of bolts that are too long or nuts hitting the adapter. Putting it in gear under a load may cause the crank to slide forward just enough to let the bolts hit. The thrust bearing or thrust surface on the crank may be worn some if the engine came out of a stick rig.
So I gut under the car and removed the dust cover to check things out. The torque converter bolts are still good and tight with no signs of them scraping against anything. The flexplate looks good with no obvious cracks or deformities that I can see. There is plenty of clearance around the starter gear. I did however, notice one of the bolts that holds the body to the frame was ridiculously loose, right near where I heard the knocking. I tightened the hell out of the bolt and the knocking is still there, but dramatically reduced. Wondering if this was the issue. Sure hope so....
Is the engine/trans rocking enough for the trans to hit the floor board or firewall when you pop it in gear? Or is there a bolt or screw sticking down from the floorboard that is just close enough to the trans to hit the trans when you pop it in gear?
That may have been it. Especially, if you say results after tightening that bolt. That would make me want to give the car a check through. It's amazing how the simple things can cause an alert.
I've been putting up with a knocking noise for a good amount of time as well. Very similar to how OP described. Hope this fixes it. Would I have to completely remove the trans or can I do it from underneath?
this bolt isn't too long is it? Pic pulled from my Rambler thread, guy said it could be bottoming out
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