I had a previous post titled Case 580SN movers quickly at idle with shuttle in forward or reverse. When the shuttle clutches engage in forward or reverse it engages very hard especially in first and second and have to apply quite a bit of pressure on the brake pedals to keep it from moving. When I release the brake pedals at idle the backhoe moves fairly quickly - at a fast walk even on small hills. I originally thought it was something to do with the forward - reverse shuttle because of the hard engagement of the clutches but after feedback from member melben it makes more sense that it is a torque converter issue. He suggested doing a test with the backhoe in 4th gear and full throttle with brakes applied. I did this and got rpm 2000 rpm which should eliminate the sprag as the problem. Melben indicated the problem is most likely excessive drag on the torque converter. That makes sense and would explain both the hard engagement of the clutches in forward and reverse as well as the backhoe moving quickly at idle once the clutches are engaged. I would appreciate any feedback on what causes excessive torque converter drag, how to troubleshoot to confirm this is the issue and of there is anything that can be done without removing the transmission and replacing the torque converter.
Blue, I as well as you would appreciate others input on this issue. in my years with those machines, I have never experienced it myself but excessive TC drag is all that makes sense if your Idle rpms are correct. Unfortunately, TCs are welded assemblies and have to be cut apart to repair, bying a reman would be more cost effective. Cmon guys, help us out!
Thanks for the feedback melben. From my experience with cars I knew if the TC is bad it needs replacement but wasn't sure if there was anything related to the problem in the control valve that could be serviced externally. With cars some say a transmission flush and fluid change may help some TC problems. I did drain and replace the fluid when I noticed the problem but not sure how a flush would be done. I plan to do the pressure checks recommended in the manual in a couple of weeks when I have time. These include TC pressure in and out, pump pressure, forward and reverse clutch pressure. I have been using Shell Spirax S4 TXM Tractor Transmission & Hydraulic Oil with good results in my previous 580 SM and SL so I refilled with that. I didnt change the transmission filter but plan to drain and replace the oil a second time and also replace the filter to see if there is any improvement. I read that using a lower viscosity oil will reduce TC drag but I don't want to to do something that will risk doing damage to other components.
I think that if a torque convertor was actually "dragging" it will soon fail and not continue to function. Something would have to cause it to drag. For example, a failed bearing or warped turbine blades. I have flushed torque convertors in the past. Even if it has a drain plug I still won't drain and flush it in a machine. The only way I found to do a complete and through job is to put it on a bench, then drain it, and flush it with solvent several times. I also fill them with oil before reinstalling them. I am not a fan of throwing parts at machine to fix it. But in the situation Blueacre is in I would replace the torque convertor, if for no other reason that it will eliminate the question of whether the TQ is at fault. The transmission filter needs to be removed and cut open to remove the paper media, and then unfold it and look for stuff that shouldn't be in it. Any tractor that will shift hard from neutral to being in gear and then start moving is not a safe situation IMHO. I am assuming that the engine idle rpm's have been verified by a method other than the dash panel display.
Not to mention, it’s back for his brakes and his legs.
I would need to know for sure exactly what the engine speeds are and what the specs are. 1. Idle speed no load rpm 2. High idle no load rpm 3. High idle torque stall rpm 4. High idle full stall rpm All the above at operating temp.
i will definitely get that info for you tomorrow but to be sure I get the right numbers I want to be sure I am taking each of the readings under the right conditions. I think the following are the procedures for 1, 2 and 3 but please confirm 1. Idle Speed no load rpm - would be rpm with shuttle in neutral and no throttle input 2. High idle no load rpm - will be full throttle with shuttle in neutral 3. High idle torque stall rpm - is the rpm at full throttle with shuttle in forward, transmission in 4th gear and brakes on. I am not sure on 4. - High idle full stall rpm - please let me know the procedure to get that one thanks Gary
Same as #3 but also with the hydraulics over relief. Its better to verify the engine speed with at least 2 good sources.
Great thanks - my son has a mechanical hand hel tach I will borrow and I am going to order an optical or laser one
Got the laser RPM tachometer I ordered late yesterday so I did the tests today. Couldn't use my sons mechanical tach - not enough room between the end of the crank and the shroud at the front. I put reflective tape on the crank pulley to read the engine RPM. First I checked the accuracy of the instrument panel tach compared to the laser tach and got the following results. Idle – panel read 970 rpm – laser tach read 951. I set the manual throttle to 1500 on panel – laser tach read 1502. Manual throttle set to 2000 RPM – laser tach read 2013 I was by myself so I couldn’t use the laser tach for the for the stall tests hold the brakes and move the hydraulic levers at the same time as using the laser at the front of the engine. Based on the above tests it looks like the readings from the instrument panel tach will be fairly close and within 10 to 20 rpm at worst. When I have a second person I will repeat the test using the laser tach for all the readings. I heated the hydraulic and transmission oil per the service manual. Transmission temperature was in the center of the green and hydraulic oil tank was quite warm to the touch. Note the manufacturer recommended RPM results (Spec) from the service manual are shown in brackets after the test readings. Test 1 – Idle Speed – 970 RPM (Spec 900 -1000 RPM) Test 2 – High idle (full throttle) – 2400 RPM (Spec 2320 - 2430 RPM) Test 3 – High idle torque stall – 2000 RPM (Spec 2125 - 2290 RPM) Test 4 – High idle full stall (same as test 3 plus loader roll back valve engaged) – 1950 RPM (Spec 1830 - 2010) The torque stall is a little lower than Spec. - 2000 vs 2125 - 2290 RPM The rest of the numbers look within Spec.