Just bought this old beauty and ran into a transmission issue. It has a Clark 2420 with a 273 converter....and seems to slip in low or high (both forward and reverse.....some movement, though not significant...crawls at about 1mph). Shifting into High "range" for 3rd and 4th.......no movement in either forward or reverse. The pressure is showing 270 from the converter. I changed the fluid, filter, checked the sump filter (was spotless) and the magnetic plug was clear. My thoughts are to: Check the pressures at the clutches (1/8NPT plug) for 260.......if good, then look at the high/low valve and then the high/low "range" valve. Any thoughts would be really helpful. I'm a closet mechanic, though far from proficient when it comes to transmissions. Thank you
Just a thought! I would look and see if the drive ring on the flywheel is trashed. Have seen this on several wheel loaders and clark cranes if it has the same setup.
If I'm getting good good pressure out of the torque converter, is there a possibility of power loss with a drive ring issue (would make a lot of noise if the case I assume) even though it's showing proper pressure ? Here's a pic of the converter on the left and transmission on the right:
Well, I removed the torque converter today to see if the fiber gear was worn.......no issue. The other issues could be a stuck pressure relief valve (as this feeds the torque converter and clutch packs if not fully open) or a weak charge pump (which shouldn't be the issue with a 260-280psi reading in cab)
I know it is not the same tranny but Good main pressure and low clutch pressure in all gears means bad modulator valve in IH dozers ,was your drive shaft spinning??
It was in low gear, but struggling. When shifted to "high" ...2nd gear......no movement on drive shaft from converter to transmission. The engine didn't seem to be "stalling" or the like. Is the modulator valve like a regulator valve? The one on the Clark 273 converter has a spool that is supposed to push open (allowing fluid into the transmission clutch packs and "wet" section of the torque converter) at 260psi. I've been registering 270psi on the gauge in the cab......so maybe the spool isn't fully opening. I know the charge pump is working (it's directly connected to the engine flywheel) and building pressure. Leaves me to believe the pressure regulating valve is "stuck".
With good pressure and the shaft not spinning I think it is in the converter and not the tranny, I woulkd open up the converter and look for broken seal rings
Opened up the converter....looked good. I'm going to check the clutch pressures in the transmission and see if that is of issue (a step I should of checked before pulling out the converter and putting back in).
What was the final problem ? I have the same issue
First-it's not the charging pump. Next, if the drive ring is badly worn it usually emits a high shrill noise that makes you think a bearing is bad. I'm going to ask what will seem like a stupid question-Did this crane come with a gas engine by some odd chance? I got this hat once is why I'm asking. The stall is of course different because the gas engine turns more RPM. It's a dog when a diesel is put in place and the converter is left unchanged. And a Clark will fool you on oil level. Check it idling. Then put it on the outriggers and get the wheels off the ground. Then put it in forward and when the wheels are spinning verify the oil level. Had a 30 ton Grove eat my lunch one time. the owner and I checked the oil a dozen times, It showed full but would try to pull and stop. Then I picked it up and tried again and pulled the dipstick when the wheels were turning and it was dry. I put three gallons of oil in it and off it went. I'll never forget that lesson. If you can determine that it did in fact come with the Detroit (I assume a 4-53?) verify engine RPM. When you get the converter back in it check that first. Check forward and reverse clutch pressure and range pressure as well and we'll go from there.
For those guys watching or coming to this thread. I have the issue with my Clark TC/Gearbox identified and fixed. Its easy to get fooled by the clutch pressure because it does not need FLOW. So PSI will be high even if there is low GPM. The TC on the other side needs a god flow rate. So measure the TC pressure with HOT oil. Mine was low but kind of ok when cold but with hot oil it went to zero ! For the C270 with the R28000 TC in should be about 50 psi and TC out about 30 psi at 2000 RPM. Before replacing the pump, the MOST likely issue is dirt ! In my case the high pressure filter was dirty AND (most important as a new filter made it better but not good) the SCREEN in the gearbox where the TC sucks oil from was half closed with dirt. Once this was cleaned I had the correct pressure and all works fine.