Knocking when pto lever engaged

[SallyO]

Was plowing snow today and a knocking noise started. It would stop when clutch was pushed in. I disengaged the pto ( lever on left side below seat.) and the knocking goes away. Any ideas what to check first? Thanks

 

[HarryVanderpool]

What make, year and model of tractor?
While the knocking was present, did the rear lift function normally?

 

[SallyO]

(reply to post at 20:00:55 12/12/21)

2 8n the lift was working while the knocking was happening

 

[HarryVanderpool]

Hi Sally,
We have a 42 Ford 2N and a 52 8N.
When either one of them has a load on the back with the PTO engaged, there is a knocking sound present.
At seems to be a symptom of the hydraulic pump design. (Scotch Yolk)
This is a common question. Also, ours has been emitting this sound for decades.
Of course, I can't hear the sound you report, but if the lift is operating properly and the hydraulic / transmission oil is in good condition, I wouldn't worry.
When was the last time the hydraulic oil was changed?
Also, it needs to be the right oil type.

 

[RM-MN]

It got colder out and your transmission/rear end/hydraulic oil got stiffer and the pump is telling you that. If you put in a synthetic gear oil the knocking will be less and your wallet will be lighter. To save money you can wear ear plugs/ear muffs and you won't hear the knocking so much. Its pretty normal and can go on for years.

 

[Abbby]

If you have not changed the hydraulic fluid lately you should do that. I switched to the lighter 134D hydraulic fluid quite a few years back and my hydraulic pump starting knocking. Switched back to the heavier oil and knocking gone. Yes it is a little slow for a while when it is -20F but I am also. Just let it warm up for 15-20 minutes.

 

[SallyO]

. The hydraulic oil is only about a year old . It was the mineral oil from tsc. It didnt knock last winter but we didnt have much snow. This year we have had lots. It doesnt knock until it warms up . I may have to change out the oil next spring. Thanks!

 

[John P.]

I found this on another site:

What youre hearing is the sound of cams/pistons in the pump banging together. When the pump is new you get a slight knocking as the lift reaches the set height.
Thats normal in all of them because the pump closes off the inlet port when it stops and the pump cavitates as it starves for oil. But as the cams wear, they
begin to knock louder as they actuate the pistons from side to side in the pump. The louder the knock, the more wear your pump has on it. Its generally not an
immediate pressing problem. If the knock is faint, you can probably put off repairs for quite a while. If its knocking loudly, you should buy a pump repair kit
and do a rebuild before it quits all together. Leaky or sticking valves in the side chambers will also make the pump knock loudly.

 

[SallyO]

Thanks for the info about the pump. Hopefully mine will
last until warmer weather and I can attempt to rebuild it.