Hi all just got my 955 running it is serial 60A10641 all checks out ok but after running it for about an hour there is a loud noise when you put trans in netural and are down at idle speed it appers to be coming fron the control valve and not the pump area. When put in gear forward or reverse it goes away then back into netural it stays quiet untill you throttle up a little. It sounds like a buzz or maybe gear mesh? The fluid is clean and full. Any ideas ? Thanks in advance. Larry

my 955h 60a-6070 made some noise at the control valve and had a seal leaking, I pulled it off to replace seals and orings and found trash on the relief valve, also if was hard to slide in housing . cleaned it and reinstalled, I have run it about 37 hrs and works great with no noise. the o-rings are not cheap, "they are cat yellow". hey Larry does your machine have d330a engine . I got mine with a valve stuck thru the cylinder wall,busted piston, and after teardown found bent rod and fractured crank. I rebuilt engine , brake bands and changed all fluids just to start with.

I did the same thing replaced the spool shaft seals. O-rings looked good the valve was clean inside. Did your noise go away with it in gear?

yes, when in gear it was quite. how much play is in your shift linkage ? maybe your valves are not going all the way back to detent. I have the service manual for mine and a 60a-84123 and up parts book which help a lot

Great idea about the detent I do have a service manual and will try that in the am. Did your noise happen when cold and warm or just warm? This is the first time this machine has been run for over two years. Thanks for the reply. Larry

Matt my machine had a valve drop on # 4 I had to put a new piston in it and went with new rings and rod bearings also. Then I took the head off my other 955 wich now needs a head. Larry

the noise was only when cold , it was last winter. I got my crank from a company in miami fl , I found them on the web. my engine was run hot due to mud in rad . I got new rod and piston and liner from cat, the other parts were aftermarket for about half the price .

Matt those yellow seals are used where higher heat is present. They stay soft better than the black seals & Cat used them for many years back in places where they were needed esp.where they are used in oil.

SJ, I did not know the reason why they were yellow, but that makes sense.
I also noticed most were thicker than the black ones . hey Larry on the right side of your trans about a foot down is a pressure bypass valve held on with two bolts. I would pull it and clean it. if trans has low pressure that can cause it and maybe some of your noise.

The yellow Cat o-rings are Silicone rubber, whereas the black ones are Nitrile rubber (also called Buna-N).
The yellow o-rings are designed for transmission/steering clutch oil applications, where oil temperatures are much higher than engines.
Don't mix the two .. if the P/N comes up as a yellow o-ring, make sure you use a yellow o-ring .. and there's little benefit in using yellow o-rings in place of black, as they are about 10 times the price of black ones.
If you're having leakage problems with black o-rings, you can go to a superior quality nitrile rubber called Viton.
Viton has superior temperature properties to Nitrile, without the excessive cost of Silicone o-rings.

www.marcorubber.com/orings.htm