Howdy guys, as the title states, I've got a Case 1155E Highlift that has low modulation pressure. The problem that warranted the check-up was that when you have all the gear levers engaged, it doesn't go into gear until around 1800 RPM (it varies) and does so with a bit of a jolt and then you're off to the races with full power. It's like having a automatic transmission vehicle, rev it up to about 1500 then shift it into 'D'. Before it "jolts" into gear, the transmission input shaft spins freely. If you rev it up to ~1500 RPM and play with the levers, it does jolt slightly as you put it in various gears, and the input shaft does slow down some, but it has basically no power to the ground, modulation pressure at that point is ~50psi. Once you rev it up enough, modulation pressure jumps up to 170psi and it slams into gear. Hopefully "modulation pressure" is the correct term, it's the pressure that the stock transmission pressure gauge would normally get, I temporarily installed my own gauge. I also installed a pressure gauge on the outlet of the transmission filter. In neutral I get 150psi @ idle, 250psi @ ~1200RPM, and WOT yeilds ~310psi. If you put the transmission in gear, take off ~10psi from those readings. I've replaced all the filters, and changed the oil. I bought this dozer with a "slipping transmission". After troubleshooting I tracked it down to the engine which I fixed, it's got great power now, once it goes into gear. After reading through the service manual, I inspected the pressure regulator in the transmission control valve unit. I pulled it apart and first off the washer was in backwards, not a huge issue but it shows that someone was likely in there before me. But the spring only measures 5.07" long when the specification in the service manual says it should be 5.66" long. I tried shimming it ~ 3/16", but that completely prevented the modulation pressure from going over 50 psi, basically it never jolted into gear regardless of RPM. Judging from the service manuals diagrams, when the pressure regulator spool is in the relaxed position, the spool covers the output port preventing any oil from flowing until enough oil pressure enters the input of the spool to compress the spring. My current novice opinion is that something is preventing the pressure regulator from opening when it should resulting in the low pressure until it finally opens and everything slams into gear. I shot this video to help describe the issue I'm having, this is with the shim removed again. https://www.youtube.com/watch?v=lZwZvD2OWjc I would appreciate any advice on this issue. Thanks!
Sorry guys, got a little ahead of myself. In the video, the gauge on the left is the "modulation pressure", and the one on the right is the transmission filter outlet pressure.
Small update: I checked the modulator orifice, no problems, looked clean. Checked the variable orifice, and the last to links are broken off the spring... fingers crossed!
There's a guy on here goes by Alrman , he is very knowledgeable about Case dozers as well as Gary Hoff . Hopefully they will chime in on your issues.
You're onto it
I sure hope so! I'm hoping to get into the case dealer in the next few days, I'll let you guys know how it goes. I will say, I don't fully understand the system, but I don't really see how the variable orifice valve would have the effect I'm seeing. Either way, I'm hoping for the best! Also, I apologize for the misspelling in my above post "last t w o links". Thanks y'all.
Welp, I stopped by the dealer. I thought they did both both agriculture and construction because I've had questions for them in the past. Turns out they used to do construction, but don't anymore. I'm in the middle of no-where USA, is there a place I could order these parts online? I'm looking to get a Variable Orifice Spring (P#A51837) and a Regulator Spring (P#A50755). I'm just a one man band, so being able to save half a day in driving would really help. Thanks again guys.
Pulled them both up on the messicks tractor that is a case ih dealer, a51837 $48.39 and the a50755 $24.38. Said 3-5 days 877 260-3528 I have used them before to ship things in. Also broken tractor, coleman. I order sometimes from the west coast depending on the time of the day to get things overnight on the east coast. You may also type you zip in on the case site and see what dealers you have in the state.
Wow! Thanks a million! I've thrown thousands of dollars at messicks, but somehow ruled them out on this, I don't even remember why. I'll be ordering from them, and will let y'all know of any further developments. Thanks Sheepfoot!
Welp, I got the parts yesterday, and installed them today. As described in the original post, it used to engage around 1800 RPM. Now after installing both new springs it won't engage at all. Modulation pressure barely goes over 50 psi even at WOT. Putting it another way, it is completely immobile right now. Thoughts?
Did you install the variable orifice spring - including the roll pin spacer inside the spring?
Yes Sir. New variable orifice spring and regulator spring, and I did reinstall the old roll pin spacer.
First thing I would try is reinstalling the old regulating spring, .5" is a fair bit of difference to spec, something not right there, wrong spring or spec. Was the new regulating spring longer than the old one??
I'll give that a whirl. Yes the new one was about a half inch longer, I only eye-balled it though. Shimming the old spring had the same effect, so I'm guessing/hoping that putting the old spring back in will at least get the machine movable. Hopefully I can get to that today, when I do I'll report back. Thanks for your advice!