SN Gw700564. I have a 2020 Cat 307.5 and I am looking for some guidance on a likely swing motor replacement. My symptom is a bounce or rebound when stopping swing in either direction, left or right. It is not just one side. Testing I have done so far: Overswing test: It stopped where it should with the bucket loaded. Swing test: Bucket approximately 6 inches off the ground all the way out. About 2 inches maximum movement over multiple tests. Swing speed test: 3 revolutions in 20 seconds each time. Swing relief test: Left side relief pressure was 3875 psi. Right side relief pressure was 3925 psi. Additional field observations: There is horizontal play only and essentially no vertical play. When stopping, the machine stops smoothly and then bounces. (perhaps 3-4 times before settling down) The symptom is present left and right. Based on that, I am thinking the swing brake inside the swing motor may be slipping and that the swing motor may need to be replaced. I was able to identify these SIS references: 522-1622 Motor & Mtg GP-Swing I would appreciate any guidance from anyone who has done this job on a 305.5 or similar machine. As always much appreciate the help from heavyequipmentforums!
Use the blade to lift one end of the machine up, this simulates machine on a slope. Stick the bucket right out just off the ground. Slew around and stop in a few locations. Does it come to a stop for a second, but then start drifting again in towards downhill? Is this ‘bouncing’ occurring during the above test?
tested it like this - there is no drift when stopping, but at a stop it will bounce to a stop, then go a little uphill bounce, then less down, then back up tiny bit. there is like 4-5 bounces as it stops, but each bounch is much less than the first.
@Chrisso So i tested it again and gave it more of an angle. when i stop there is a drift of about a foot or so past where i would have wanted to stop. i did the RPM up a bit too, my first test i had it at low and missed the point you may have been making. so with it on an angle from the blade - when i ask joystick to stop - it will continue past that point for about a foot - or even 2, then it stops and bounces back and forth 4-5 times before comming to a rest. doing it like this made the machine feel aweful - after a few times i was worried im gonna break something that is givng me trouble. aprreciate any other input @Chrisso
Ok, it doesn't sound like the classic failed cushion valve symptoms, but I think it's worth ruling the cushion valve out. Down in the guts of the machine, under the centre cover, next to the slew motor, there's a valve mounted on the firewall, it's right down the bottom. It has two relief valves mounted on opposite sides and only had two hoses going to it. Pull the hoses off and cap them somehow. Repeat the test. It should slew properly as commanded now but will be a little clunky coming to a stop. This is normal because you just removed the cushion valve from the circuit. You should not get any uncommanded movement (or bouncing) now. Does this happen?
Cancel that, the stupid thing is the 307.5 doesn't have the cushion valve, so no need to rule it out, that'll teach me to check before posting. So the swing relief valves are mounted on the main control valve. I'd be removing these and making sure the o-rings are intact and there's no metal/debris jammed in them. I think it's also worth cutting open the hydraulic filter and checking for same. It wouldn't hurt to have a laptop on there to see when the swing brake is engaging, and if it is engaging at the appropriate time.
Just to clarify on the swing subject. Swing motion is stopped by sealing off the oil supply. Captive, deadheaded, oil in the motor does the actually swing stopping. The cushion valves mentioned above soften the hard stopping from the oil circuits being closed. In fact, on most machines the swing brake releases even when only a boom, bucket, or stick request is made. The swing brake does nothing but preventing swing motion when parked, and, more importantly, doesn't apply until several (usually 5 to 6 seconds) after hydraulic requests are no longer made.
I'd also check the swing solenoids for the same debris. They're also in the main control valve. If it is worst case ie swing motor failure, you don't want debris destroying the new motor also.
A friend of mine had a 308 about 2020 version that the swing destroyed the entire machines hydraulics with only one month of warranty left. Every hose, valve, pump, motor had to be repalced or rebuilt. As @Chrisso said I would have a look in the hydraulic filter in case you find a surprise Simon C
ill get the swing relief valves out and inspected - If i cut the hydraulic filter, will i be able to see the metal if there is any? -ive never cut one to look for debris and would not want to miss what i should be looking at. @Chrisso @Simon C
When you cut the paper section out and squeeze in a clean vice to get oil out you will see if steel or bronze is in it. Filter cutters are pretty handy. Maybe someone you know has one. I have one and used it a lot of times. Simon C
See this video. I know it’s an engine filter but the same principle applies.