New old guy needs help 300U knock

[lmmare]

Hi all,
I was a member here a while ago but life managed to pull me away but I'm back and could use some help.

I've got a 300U that I've owned at least 40 years or so, great machine that I have run hard and maybe put away wet too many times. Anyway the other day driving down the road 4 hi, there was a click, for the lack of a better word, then knock knock knock. Eased it home and now I'm getting ready to tear into it. The sound reminds me of a car with a bad main bearing. The knock is engine speed related, clutch in or out, but the funny thing is it sounds like it's coming from the transmission area more so than the engine. Other than the knock everything else is normal just like it's always been.

Looking for suggestions or maybe someone's had this before. I'm thinking the only thing running in the transmission with the clutch in would be the pto, but it seems fine too. So tomorrow I'm going to finish power washing her and get her ready to pull into the shop. I would just like a better idea of where to tear into besides starting at the front and working back.

So Help!

Thanks, Lance

 

[rustred]

get a video of this knocking. funny how no explaination of your oil level or checking it. was it knocking all the way home? if you reved it
up does the knock change.? better get it dia gnosed before a tear down. is it knocking parked?

 

[lmmare]

Oil pressure/level good, knocked home, knocking now parked. Knock follows engine speed. Getting it diagnosed is what I'm trying to do here. I'm in West Texas, closest old tractor mechanic besides me is probably 600 miles away.

 

[rustred]

does it get louder on decelleration when reved up?

 

[lmmare]

I would say no, the volume seems to stay the same at any point.

 

[rustred]

its not a rod then.

 

[rustred]

hows the blowby?

 

[lmmare]

All looks normal

 

[Janicholson]

The clutch pressure plate has a spline in the center that drives the PTO for Live PTO. This spline drives a tubular shaft that drives the PTO through a set of spur gears. So, if a tooth was off of those gears, it would make noise, clutch in or out, the splines and drive tube can also fail. #4 and #8 are the drive tube and gears.
I would take the spark plugs out, and with the engine ignition off, i would have a helper turn the engine (a crank would be nice, but by hand with the fan is OK. and while that was turning, I would hold back the (engaged) PTO carefully feeling for a skip or click in the shaft rotation. Noticeable felt noise there defines that issue. If smooth as silk, less likely. JimJim
Exploded parts view

 

[lmmare]

Thanks I will try that tomorrow, I have been using the PTO pretty hard for the last year or so running a beltek Auger, that would help explain why the noise is louder past the t/a

 

[the tractor vet]

welp the easy OLD way is to take a LONG wooden handled screw driver and with it running hold the end of the screw driver mid way up on the block and put your ear to it starting at #1 and working back , move from mid way on the block down to the bottom of the block and up to the head on each hole . Ya find nothing there keep moving back on the tractor , Ya may have a piston coming apart , a wrist pin getting loose or a rod bearing going to lunch or ya may have a cam gear headed south .

 

[lmmare]

Thanks that's a trick I haven't thought of in 30 years or so , I'll be giving that a try tomorrow!

 

[rustred]

It could be a chunk of carbon came loose and is now on
the piston hitting the head. Dont know what pistons u
got though. U can even cut the Mrss broom handle down
and use that.

 

[IHRON]

I bought a 300 utility with a knock. The ball that supports the
front axle, under oil pan had come loose. The u shaped support
was riding on oil pan, bent oil pan up, making knock when crank
hit axle support.

 

[lmmare]

(quoted from post at 22:18:37 08/03/23) It could be a chunk of carbon came loose and is now on
the piston hitting the head. Dont know what pistons u
got though. U can even cut the Mrss broom handle down
and use that.

This is a work tractor run pretty well every day, I'd find it hard to believe it has any carbon build up, but I won't say it doesn't.

 

[lmmare]

(quoted from post at 05:01:24 08/04/23) I bought a 300 utility with a knock. The ball that supports the
front axle, under oil pan had come loose. The u shaped support
was riding on oil pan, bent oil pan up, making knock when crank
hit axle support.

Now that is something that I've had happen a few times as my socket for the ball is very worn and allowed the pan to be bent in as you describe. I have had the socket spaced out with washers for years so that wouldn't happen anymore, but it was the first thing I checked.

This post was edited by lmmare on 08/04/2023 at 05:50 am.

 

[300guy]

If you think it is carbon on top of the piston, get a water bottle of water and pour a little down the intake while the engine is running 3/4 throttle. If it starts to die just stop pouring. Do most of the water in the bottle or until the knock stops. The water will form steam and cause the carbon to soften and eventually break up and go out the exhaust. Have used this trick a lot of times. If it doesn't stop then you probably have another problem.