Purchased a 515c a few months ago knowing it had a problem dropping into reverse when the trans oil got hot. Trans fluid would get hot and say hot under a medium load such a roading in 3rd range. Anti freeze was pure. Diluted it up to -10F. That cured the short term heating prob. Brought it into the shop and drained all the fluids. Trans is WAY over full.Change all filters and clean suction screen on trans. No clutch facings or metal chunks. Refilled the trans with ISO 32 Premiun hyd fluid . Previous owner said it was losing hyd. fluid. Replaced a leaking hyd hose to a strg cyl. Next day the trans is over full and hyd res is low. Weep hole is plugged on hyd pump and seal is out. replaced seals and think I have this thing whipped. Take it out and use it around the yard spreading rock etc. 45 min the engine oil pressure light flickers. Pull dipstick no oil. Yup trans is over full again. Early 5.9 cummins had a issue with rear main seal crawling in and spinning on the crank. Pull engine and replace seal and housing. Take it out and use it for an hr. under medium load and all is well. shifts forward to reverse like it should. Trans fluid temp stays in the lower third of the green (normal operating range). Move it out to a pasture with a lot of 10 to 30ft. trees and give it a workout. When I would work the torque converter hard the trans temp would go up to the middle of the green and hesitate between shuttle shifts. When it shifted it was a positive engagement not a mushy woreout clutchpack shift. Work it hard enough it stopped completly until it cooled a bit then away it went. Put a pressure guage on the main system port and the pressure stays at 300 psi spiking down to 100 when shifting and recovering instantly. When it stops shuttling the main pressure will drop to 100 and stay there until the shift is made. If I shuttle shift under high rpms it will usually complete the shift when hot but I'm not to keen on that procedure. Noticed the trans oil was foamed up with big bubbles like soda pop bubbles (not milky). Talked to a oil dist. and he came back with the idea to use Cat spec.TO offroad trans oil. Supposed to have more anti foam additives . Made it worse. I start to think it has got to be sucking air between the charge pump and sump. No leaks. Pull Charge pump and check pump shaft seal. Looks good pull a vacuum on pump still good. Let it idle in neutral for an hr and the oil stays air free. Use it there's bubbles. Torque converter? Am at a loss. TIA Dirt
Not sure how the Dresser trans is set up, but I had a Clark trans do a similar thing and found that there was an internal steel tube from the suction screen to where the suction hose connected to the trans. The steel tube had a crack and under medium load wouldn't suck enough air to notice but under full load it would pull enough air to foam the oil and cause the convertor to overheat.
Way back when I worked on Dressers the transmissions ran on Hytrans or what became tractor hydraulic fluid. How many hours do you have on this machine? It sounds like you have a torque converter problem. You can usually tell by running stall tests before the machine is warmed up fully. Put the trans in third gear after the engine has run for five or ten minutes. Max out the throttle while holding the service brakes on. Make sure your brakes will hold the machine, if they won't then you will have to fix that first. Watch the torque converter temp and the water temp gauges. The torque temp should run up fast. Let off the throttle and take the machine out of gear. Now run the throttle up in neutral and the torque temp should drop like a rock and the water temp should start to rise. Do this a couple of times and you will get an indication of how your torque is working. Make sure you do not let the torque temp hit the red on the gauge! There are some hook ring seals in that beast that fail from time to time allowing oil to bypass directly back the transmission drop box instead of going on to the cooler. Since you already changed the filters and cleaned the strainer, I'm thinking you didn't find any aluminum or you would have mentioned it. Good Luck!
Thanks for the replys. Did the third gear test hunkered down under a big elm. Trans temp shot way up then cooled right down when I put it in neutral. Coolant temp climbed. Forgot to tell about that test. Am thinking about putting hytran in it for s and giggles. The internal leakage scenario interests me. An ag engineer friend told me that the bypass/return dumps arn't always placed where they should be and cause foaming. The loader shows 1100 hrs. As tight as the hinges and pins are it can't have a terrible lot more than that. History of the loader. Bought new by the local township. I loaded some gravel with it probably 15 yrs ago and it would quit shutteling then just like it does now. Wasn't my problem then. Township sold it to a local gravel hauler with 2 single axle dumptrucks. When he got a bellydump the old girl couldn't keep up so it sat for a couple of years. No debris at all on suction screen. It's loading aglime on to a field spreader right now so light duty is it's calling. But it really grieves me that I can't come up with the cure. Any suggestions or tests to do would be appreciated. Dirt