JD 450B Won't Move

[Craig Ridge]

Need some help...

My JD 450B crawler/loader won't move. It stopped driving in either direction while lightly pushing a small bucket of dirt on level ground. Previous to that (when we purchased the machine) it seemed to lack the strong forward pushing power I expected, but everything worked. At no time have we heard any loud or unusual noises from the engine or the drive train to include when the problem occured, or in subsequent troubleshooting and test running.

Here's what we've done so far:

• Changed the transmission/final drive oil to JD 303 equivalent oil. While transmission was drained, we removed and inspected the internal screen filter in the bottom of the transmission (it was clean and LN). Oil level is now at the full mark.

• Topped off the power steering reservoir which was quite low, but not empty.

• Performed the clutch pedal adjustment and the clutch valve linkage adjustment per the manual.

• Checked the tranmission oil pressure which is 170-180 psi at about 1800 engine rpm. When shifting the LH-R lever, the pressure drops to about 100 psi, and then returns to 170-180 psi.

• Brakes and steering levers have been adjusted exactly as instructed in the manual. There are no visible signs of oil contamination in the area under the brake/steering clutch covers on either side.

• Checked the power steering pump pressure as per the manual. Deadheaded, the pump pressure is about 175 psi which is below the required spec of 210 psi with a relief valve setting of 275-340 psi. (Note: We suspect our guage may be reading about 25 psi high.) With a Tee installed in the line, the steering pump pressure is 50 psi with both steering levers in neutral. Pulling either lever causes the pressure to instantly increase to 175 psi.

• When the foot clutch pedal is depressed, engine rpm increases slightly and then drops back to the previous rpm. When the pedal is released, engine rpm slows down slightly, and then returns to normal.

• We removed the final drive center top cover to see if the input shaft from the transmission to the final drive was moving. It was not -- regardless of the position of the four speed transmission lever, or the LH-R lever. Both transmission levers appear to be working correctly and external linkages are intact.

• Both tracks move freely when using the bucket to push the crawler backwards.


At the moment, we're reasonably confident the problem is in the transmission itself. Before we tear into that, I thought it might be wise to seek advice/guidance from others who have more experience with this machine.

Have we overlooked something? Any advice on how to proceed from here? We'd appreciate any help anyone can offer. Thanks!

[gerald]

Craig. I think your 450 B has a engine clutch.

[Craig Ridge]

Update on the still unmoving JD 450B:

Today we removed the top cover on the HLR transmission and confirmed that the engine clutch was working exactly as it was supposed to work.

• When cranking the engine with the starter, the HLR input shaft spun around with nary a hitch. Depressing the foot clutch caused the engine to spin over by itself.

• We then turned the HLR output shaft by hand and were able to take up all the available slack in the final drive in both directions (neither of us was strong enough to move the loader by twisting the HLR output shaft by hand).

• The inside of the HLR was spotlessly clean, and looked as if it had been recently reconditioned. There was no smell of burnt oil, nor was there any discoloration on the exterior of the three clutch housings. All of the individual clutch plates separated from each other (moved freely within the limits of their travel) with the mere touch of a fingertip. Obviously, we couldn't see the clutch faces, but I'll be amazed if we subsequently learn any of them are burned and/or glazed. We also couldn't examine any of the three clutch pistons, but I think it's highly unlikely all three would start leaking at the same time.

• The corresponding input and output shafts move in lock step with their associated clutch halves (but not with each other), so I'm fairly confident none of the clutch disk splines are stripped. Plus, none of the tangs on the outer rims of the disks appear to be broken off.


Our next step is to remove, disassemble, and inspect the Clutch Control Unit and shift valve. I don't know what we're looking for exactly, but something isn't right -- we have engine power coming in, and nothing getting out to the final drive.

Transmission oil pump pressure is at 170 psi, and we appear to have about a 10 gpm flow rate. Something is going awry between the pressure test point and the clutch pistons -- no (or low) oil pressure in the pistons, and nothing is going to get to the final drive.

There is a small filter screen in the accumulator body that could be plugged, or possibly some control valve spring is stuck or broken. Other than those items, we're pretty much running blind.

If anyone has any suggestions at this point, we'd like to hear them. Thanks!

[digitup2]

Check your power shift pressures you really can't tell just by doing that you have to check the pressure while running and go from there .Digitup.

[Craig Ridge]

Check your power shift pressures you really can't tell just by doing that you have to check the pressure while running and go from there .Digitup.

So, how does one check his "power shift pressures"? The Technical Manual only specifies ONE test pressure, and our setting has been adjusted within specifications.

If there are other pressure test ports on the HLR transmission, the Technical Manual doesn't reference them, and we haven't found them by visual inspection either. If they exist, we'd certainly like to know their location and how to use them!

Thanks for your help, but we need more specifics....

[digitup2]

You test the pressures as you shift and look for pressure drop and at what point that tells you what is leaking and where .Digitup.

[tjdub]

If you try to shift ranges without pushing the clutch in does it grind? Since your pressures all seem to be up, I have to wonder if there's some problem with the shift linkage and it's stuck in neutral or between gears.

The engine clutch doesn't work on mine, so I either have to put the HLR in neutral for a really long time, or just turn the engine off to switch ranges, otherwise it grinds. If yours runs through the gear ranges without grinding while it's running and the HLR is in gear I think that may point to a problem with the shifting linkage. On the other hand, maybe it won't tell you anything, but if it does grind I think that will mean that it's definitely a problem with the hydraulic clutches.

Edit: nevermind, that wouldn't match the symptoms of it being weak as the problem developed.

[dmuff]

This sounds much like my 450c. Power in. Pressure good. Mine has a winch and it was working. Just found out that the rivets on the ring gear in the rear of the transmission were stripped.

I could also shift gears while the transmission was in HI, LO, or Reverse without using the clutch - no grinding to speak of.