1956 Noise coming from torque converter area

[hd78half]

Our '56 Bird is making a knocking noise. Has been doing this since acquisition 3 years ago but seems to be louder this year.

Checking with a good stethoscope now indicates that the noise is coming from the area of torque converter. Engine and transmission were recently rebuilt and it doesn't seem to be a bearing noise - the oil pressure is good and there's no change in the noise whether the engine is cold or warm.

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[74 Harley]

Have you checked the torque converter bolts yet? I would start there.

 

[doug7740]

The 1955/56 air cooled automatic transmission flex plate has six mounting points to the torque converter. The mount tabs are secured to the flex plate with rivits. The rivits sometimes loosen and create a noise, which in a lot of cases has been diagnosed as an engine knock. The 1957 automatic transmission flex plate is stamped from heavy steel plating and is a replacement part for the 1955/56 models. If the mount bolts are over tightened or loose, it could crack out the mount holes resulting in a knock when the engine is running.

doug7740
1955 Thunderbird Blue

 

[hotrodbuilder]

Our '56 Bird is making a knocking noise. Has been doing this since acquisition 3 years ago but seems to be louder this year.

Checking with a good stethoscope now indicates that the noise is coming from the area of torque converter. Engine and transmission were recently rebuilt and it doesn't seem to be a bearing noise - the oil pressure is good and there's no change in the noise whether the engine is cold or warm.

I have found the torque converter bolts to the flexplate loose on a couple of these early Fords. I would check that first. If they are loose for a long time, there is a good chance that the flexplate will have elongated holes and will need replacing.

 

[hd78half]

Thanks for the comments on the flex plate. The engine has one of the after-market flex plates and I've confirmed that the bolts are tight.
After removing the torque converter inspection plates (to check the flex plate bolts) and starting the engine, the "knock" now seems to be more localized in the engine lower end, near the rear. Very apparent with a stethoscope at the rear of the oil pan. Noise doesn't seem to change with temperature, and oil pressure is good (60 PSI cold and 20 PSI at warm idle). Engine rebuild has <50 miles on it. Will continue attempts at diagnosis and post when something concrete to report.

 

[74 Harley]

You need to contact the rebuilder immediately. You have a problem that will not correct itself. Hopefully they will honor a warranty of some kind for you.

 

[steven shafer]

Our '56 Bird is making a knocking noise. Has been doing this since acquisition 3 years ago but seems to be louder this year.

Checking with a good stethoscope now indicates that the noise is coming from the area of torque converter. Engine and transmission were recently rebuilt and it doesn't seem to be a bearing noise - the oil pressure is good and there's no change in the noise whether the engine is cold or warm.

It is probably your flex plate. It’s a thin plate that goes between the crankshaft and torque converter. A bad one would sound just like a bad rod. You will probably have to remove both the transmission and engine together to replace it. It can’t be repaired. After replacing the flex plate you should make sure that you have crankshaft play front to back. You would use a long piece of metal, like a crow bar, and move the crankshaft front to back and make sure that it moves at least a little bit. If it doesn’t move then you will ruin your crankshaft and engine because the crankshaft is rubbing on the engine block. The new flex plate could be too thick, I had to custom make some cork shims and put them between the bell housing and transmission to get the proper play. I have been driving like this for about 20 years with no trouble but can’t seem to get any vendors of the flex plates to believe me on what I had to do. There doesn’t seem to be any original flex plates available anymore.