growling noise when lift arms are near top of stroke

A friend asked me to put his lift cover back on after someone else started and never finished the project. It is a 48-50 8N and when I got it they had purchased a used 9N cover to just "drop it in" rather then repair the original cover. I was told in the
beginning the problem was there was no draft yoke, spring or plunger. Just the open hole in the back of the cover. The draft link 8N-540-A2 was missing on the original
so I got one from Just 8N's along with the gaskets I would need. I took the yoke, spring, sleeve, plate and plunger and stuff off the 9N cover. I have a Zane jig for
setting the control rod position. I followed Zane's instructions or the FO-4 service manual when appropriate. The lift works as Zane's instructions indicate it should in both draft and position control. The problem is when you get near the top of the stroke there is a obvious growl. If you look at the reference marks on the cover and the lift arm it's about the last 3/16" of rotation. What would cause that noise? Any suggestions? I appreciate your help.
Greg
 
Does the growling continue after the arms have reached full extension?
If so, then the pump is not getting relief from pressure at the end of arm travel.
If there is growling just for a part of the travel then binding comes to mind.
Hope that helps.
Greg
 
If the control rod was not completely straight the neutral positioner dowel that should contact the edge of the piston when fully extended may not be doing so.

Does it do it in both the position and draft mode? If it does then it's for sure the neutral dowel is not performing it's role.

Zane
 
Except to reference to parts I do not recommend trying to use that FO manual with my instructons and jig. It is impossible to correctly adjust the lift linkage using that FO information with an old worn lift linkage. Got to have a positive reference point such as the jig.

Zane
 
Zane, it does make the noise in both draft and position control. As to the control rod being bent, it was straight if you were to look at it from the rear of the tractor looking forward but it DID have a very slight bend in it if you were to look at it from the side of the tractor. I also lifted our camper trailer up which has a 710 lb. tongue weight and it leaked down 8" in 5 min. 30 sec. I also found out the growling sound is there all the time when your lifting when you have the 710 lb. load on it. With no load the noise is only at the top of the stroke. I believe my friend will only be using it for mowing with a rotary cutter so the leak down does not concern me (I think) as does the growling noise. Thanks again for your time.
Greg
 
Zane, I was only using the FO manual to be as familiar as possible with the lift cover / hydraulic system. It has been 10 years since I worked on one and I needed all the information I could get. But I remember from last time not to try to mix apples and oranges on the adjustments.
Thanks
Greg
 
Thanks to everyone help I was forced to look harder at the problem and it came back to the basics. At some time the check chains attached to the lower links had the clevis hooked to the second link in the chain rather then the last link. So when the lift was near the top of stroke it would start binding the chains and the growling noise would start. Apparently the pump is worn or has another issue that causes to noise. The owner does not want to get into $$$ that repair so I returned the tractor to him. Thanks again for all your suggestions.
 
If the bend is concave toward the front of the tractor it could well be causing the piston to not be able to contact the neutral dowel at maximmum lift that is attached to the control valve long rod.
I have seen them with bows like a rainbow and it's usually caused by a sticking control valve. If it has a sharp bend it is caused by a dummy!
Zane
 

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