57 hydramatic trans knocking noise

[Renato]

Gentlemen,

I have a strange problem with my 57 transmission. It works and shift fine, but it has a knocking noise in middle-high rpm. It sound like a steel ball knocking in the transmission. If I put in N position at 50 mph the noise disappear. After I shift it to Dr it comes again. So I1m sure it comes from my trans. Anybody have any idea what could it be?

Thank you!

[Roger Zimmermann]

It's not the drive shaft? I cannot imagine how a transmission can do a knocking noise in a specific range. If you put the selector in D3 do you still have the noise, or at a lower speed (like RPM related)?

[Renato]

Hi Roger,

I changed the output shaft on the trans. It was weared. I also put new U joints. I will lift it up to see what's going on.

[Roger Zimmermann]

Did you check the central bearing from the drive shaft?

[dn010]

I would also suspect the support bearing, mine was making noise until replaced many years ago. The reason the noise disappears in neutral is that the driveshaft is turning freely and not under torque from the transmission.

[V63]

Check mountings too

[Renato]

Mountings new, i will check the rear bearing tomorrow. Thank you

[Burt6666]

Check torque converter and bolts

[Renato]

Good news! The drive shaft knocked the trans. rear housing. There was a small dent and touched the shaft. Thank you everbody

[Chopper1942]

I don't quite understand how the driveshaft would hit the trans rear housing and dent it and make the knocking noise only when there is a load on the drivetrain. The front driveshaft yoke should never move far enough to hit the trans housing. The front driveshaft is held in basically a stationary position by the center bearing.  The only way for this to happen is if the splines at the center bearing are dry and do not slip and the rubber in the center support is bad.  then when the suspension moves up and down it could push the front driveshaft forward.  Normally the yoke sits back about 1"-1 1/2".  Strange? 

[Dave Shepherd]

I don't quite understand how the driveshaft would hit the trans rear housing and dent it and make the knocking noise only when there is a load on the drivetrain. The front driveshaft yoke should never move far enough to hit the trans housing. The front driveshaft is held in basically a stationary position by the center bearing.  The only way for this to happen is if the splines at the center bearing are dry and do not slip and the rubber in the center support is bad.  then when the suspension moves up and down it could push the front driveshaft forward.  Normally the yoke sits back about 1"-1 1/2".  Strange? 

Agreed, plus " a dent in the housing" can't  see that happening.

[Chopper1942]

I think Burt6666 is on the right path.  I have seen loose converter bolts and loose flywheel bolts cause the noise that Renato describes.  This would be my guess as best place to start, since I can't hear the noise and comfirm where it is comming from.

[Roger Zimmermann]

Just for your information, those cars have a fluid coupling, not a torque converter. However, your thinking about loose nuts is something to consider.

[Chopper1942]

Yes, I know.  Miss spoken in the heat of responding to a 57 Hydra-matic issue. What I stated applies to all automatic transmissions and some "standard" transmissions whether they have a fluid clutch, fluid coupling, or a torque converter. Still, if one of the multiple bolts holding the fluid coupling together is loose it can make contact in the "bell housing". Especially if there is excessive crankshaft end play.