The transmission suction screen housing is stuck on my Case 850D. When I tried removing it with a 1.5” 6-point socket and long-handled ratchet I was concerned I would break the mounting bracket off the frame, so I removed the complete assembly. Past posts on this subject recommend using a chain wrench on the housing instead of the hex on the housing. I’ve only used a chain wrench on steel pipe. My concern for this application is warping the aluminum housing, but is the risk of using the hex greater? The hex molded in the housing is in good shape. The joint is soaking in Kroil right now.
It broke loose with a loud pop this evening. Used the socket and a 3/4” drive breaker bar. The filter was full of varnish flakes. I always have the oil analyzed when I buy a used machine. The analysis revealed varnish particles smaller than the filter rating.
Varnishing is a pain to deal with. We use side stream filtration at work on our turbine oil systems to prevent it. I woner if changing the oil filter a few times and then changing to oil would help?
I'd never seen that much varnish. Varnish is generally formed when the temperature limit of the lubricant is exceeded. A retired heavy equipment mechanic said he used to see it in the transmission filters on smaller machines that had been overworked or had slipping clutch packs. I bought this machine back in June. It has less than 4000 hours, but I'm finding evidence those were hard hours. I cleaned the suction strainer and changed the oil and filter. Used the last of my TCH, hope I can get some more. The oil analysis picked up the varnish, so I'll sample again after 50 hours and see what it looks like.
We see it in tight tolerance valves that see allot of heat. The varnish causes the valves to stick or drag. The amount of drag we see wouldn't cause an issue in 99% of equipment but can be an issue for us. We had a Case 850G for several years and I loved that dozer. We really should have kept it but it was time for it to go. I always had to order the TCH fluid. Not sure on the D model but the G had a hydraulic filter in the hydraulic tank and a transmission screen on top of the trans.
Before the transmission service the trans pressure fluctuated a lot on the gauge. After the service the pressure only fluctuates slightly. Could be the clean screen or could be the TCH (lower viscosity than Hytran). Maybe a little of both. My 450C transmission was more responsive after I switched it to TCH.