51 B trans noise

I am trying to diagnose a loud noise coming from (at least appears to) the transmission. It seems loudest under the platform but in front of the seat. I know sound travels but it seems lodest there.
I do not know if this noise has been there a long time or not. This tractor has not had a muffler since I've been alive. I just started making some minor repairs in recent years and put an exhaust pipe and muffler and now I can hear this noise.
I use the tractor for plowing and cutharrowing and do not want to run to failure to find it.
If I engage the clutch the sound lessens slightly. Moving it in any gear or engaging the PTO doesn't seem to make a difference.

Any tips on where to start looking would be helpful.

I have a complete shop manual and parts catalog to aid me.

This was my father's tractor he bought in 51. Since his passing I have been tinkering to replace some broken or worn out external parts.

Thanks in advance for any help.
Rich

So is this noise only with the engine running and you are not moving ?
Is it a knock ? or a growl ?

Might be a loose flywheel if it's knocking.

Try changing the trans oil (don't forget the 1st reduction gear-if applicable). HTH

The transmission can't make noise if the tractor is sitting still and the pulley is not rolling so when you say it lessens when you engage the clutch I think "engine issues". I would look first at the clutch driver and the flywheel. Then inside at the rods, mains & piston pins.

Another item to check..... Remove the mag/distribtor and pull the throttle back until there is no tension on the governor spring. Not all the way back but into that neutral area just above slow idle where the carb is open about half way. If you have a dial indicator, set it up & measure for run out on the governor shaft. If not available, just grab the drive coupling with a pair of locking pliers then push in & pull out on the coupling which is hopefully tight on the shaft. You should not detect any play in the governor shaft. The shaft should not move in, out or wobble at all. It's supposed to be under rather stout spring tension with zero play.

Moisture (crankcase condensation) collects up here and the right bearing's outer ring will stick fast in the governor housing's rusted bore. Once stuck, the right bearing spring can no longer keep the shaft tight. At certain speeds and loads they'll rattle. Not a hammering but more an intermittent vibrating rattle or growl. Slight speed changes and load changes can make it come or go. Sometimes just opening or closing the shutter can make it come or go.

Hope this helps.

Without being there and hearing the sound..the 1st thing I would suggest is that you GREASE the Front Fan-support Bearing..
The sound from that bearing squalling can travel all over..!!

Ron..

Our 2 JD "B" (Late Styled)STOPPED burning valves, when the original mufflers rusted off...never burned another valve and never had a muffler on either one since...

JD had a steady order to come and get one, when the other was ready to be sent back to us...went on for 2 to 3 years...

And NO, they were not run Lean and the Valve-Jobs were all done by JD in Plain City, Ohio..

Ron..

Thanks everyone for the replies.

The noise is a growl and is there moving and standing still.

I changed the transmission oil and it made no difference.

Thanks for the ideas and things I can look at.

Rich