Our year-long efforts to get our LS 4300 CII to travel are getting close to success as we've repaired and corrected so many issues on a machine that might have been otherwise condemned to junk. We've rewired and made a new control panel and run in bypass mode as the original computer was long gone. The rotary joint had been resealed prior. Unknown to the previous owner the main pump was going out and the pilot pump was being taken out due to bad bearings in the main pump. All of this has been corrected, the hydraulic tank cleaned (no significant debris found), filters changed including pilot filter, and new hydraulic fluid put in. Pilot pressure is around 600 psi (near spec) and pump section pressures look good. When travel is imitated it appears that there is major bypassing in both travel motors as the case drain hoses both jump excessively when forward or reverse travel is initiated. Pilot pressure has been measured at the test port under the cab as well as at the pilot filter (we installed the second port there when replacing bearings in the pump). It appears at first that the problem is failed seals in the travel motors, but for both of them to have failed in the same manner AFTER the machine had been walked to it's current location to have the rotating joint resealed, then no travel after seems illogical. The excessive bypass of fluid through the tank drain hoses is obvious. Am I overlooking another possibility here? You folks have been incredibly helpful for the past year and are the reason we now have a machine that appears to be running strong and clean, good swing, arm, boom, and bucket operations. But NO TRAVEL is the remaining issue. I hope some good advice will vistit us once again! Thanks - Tom Fischer
Is there a chance the previous owner didn't hook up all the lines correctly after resealing the rotary joint??
You stirred up some old memories in the deep recesses of an old and tired brain that perhaps I wanted to forget. The 4300CII models had some issues on the travel motors that were inherent in design. When the motors started to go bad they would go into high speed and would not run in low. In those days I believed the problem was because the shift piston for high range would start leaking by. The motors would be torn down and nothing was found wrong with them. We would reinstall them and they would be stuck in high all the time. We would install new motors and things went back to working properly. What I would suggest is first to make sure the two speed travel lines did not get swapped with the case drains. If that is proper, then you will need to do a case drain test on each motor. Pull the case drain hose off the motor and cap it. Attach a short hose to the motor and put the open end in a bucket. Lock up the track with a pin between the sprocket and against the track frame. Put the engine at high idle and run the track over relief. You should get at most maybe a quart of oil in a minute of stall. If more than that, the motor will have to come out and be torn down. Good Luck
We were hoping that might have been the case but we checked and there's no way the hoses at top and bottom of the rotary valve can be switched. The case drain hoses are ~5/8" and tee at the bottom, while the two-speed shift hoses are ~1/2" and also tee on the lower side.
What about at the motors themselves?
As always, thanks for your sage and wise advice John. I will head up tomorrow to see what hydraulic fittings will be needed to block the line(s) and plumb the case drain for a hose. I don't think the hydraulic fittings are JIC but I may be wrong. What I had assumed to be 1/2" pilot pressure hoses going to the sides of each motor are apparently the two-speed shift spools? And the ~5/8" lines are the case drains? I have made some uniformed assumptions along the way and this is just another example. I have the manuals and will study more about the travel motor operation. We are running in bypass mode with dedicated toggle switches wired to each of the 10 solenoids on our machine. One of these was for "two-speed" which I didn't fully understand to any depth at the time. I think things are getting clearer now for me and will do the case drain check that you have recommended. Thanks again! -Tom
The motor hoses match the shop manual drawing placement.
Hello again John. I'm trying to get my head around the travel motor operation and, if we need to, how to remove it. The motors have JIS (Japanese) fittings and I've purchased a substantial stock of caps and plugs for the four lines that connect to each motor for test and (maybe) removal and shipping purposes. This is what I have gleaned in my understanding so far. The smallest of the four lines is ~1/2" and I assume from the hydraulic diagrams that it supplies pilot pressure to release the travel brake in the drive when control is initiated. The next size up is ~5/8" and assumed to be the case drain line. Both of these lines jump substantially when travel for either or both motors is initiated. Your mention of the two-speed travel lines has me baffled unless we're talking about the two large hoses that show both pressure and relief for each P1 (lower hose) and P2 (upper) line. As I think I understand the two large ~7/8" hoses are apparently bi-directional with the upper hose connected to valve pressure from pump section P2, and the lower hose connected to valve pressure from pump section P1. Flow direction is depending on forward or reverse travel. Please correct me if I'm wrong so far! I'm having trouble deciphering the hydraulic diagram in our shop manual, thus my slowness in understanding. Per your advice we're going to do a tank bleed test by capping the hose of each case drain line while stalling the travel (easily done since the dirt and mud build up from 10 years of not moving achieves that for us!). Just how high pressure fluid is valved within the body of the motor when changing rotation is still undiscovered territory for me at the moment. But I will continue to study the shop manual. What I have NOT found so far is removal procedure for the travel motor(s). I watched a video on Youtube for another Japanese machine that shows the track being removed from the drive sprocket and the travel motor being pushed outward with assistance of a skid steer. Though we have our big backhoe to assist, the idea of pulling a track on a 75,000 lb machine is daunting. I thought pulling and replacing bearings and pilot pump on our machine was going to be the hardest job we've faced but I finally handled that one well after pulling and reinstalling the pump 4 times. Pulling the travel motors has me worried though! Is the motor removal pretty much the same as I described above? Since both tavel motors exhibit the same apparent "bypass" issue I'm hopeful that a simpler cause is found. Thanks, -Tom Fischer
"Over relief" caught my attention. Would relief dump into the case from a relief valve in the case? and could it be that the machine had been run in high long before we bought it? There is a two-speed solenoid that we have on a switch since the machine is running in backup mode (no computer). If so our no travel problem might be because of the heavy dirt and mud build up under and in front of the tracks, and possibly our engaging the two-speed travel solenoid in high range. I'm going to try raising one side, then the other of the machine since we have all other functions. We'll then try travel to see if we get the heavy by pass through the case drain lines. -Tom IMG_1768.JPG
The two large hoses are for forward and reverse. The medium size hose on the top is case drain and the small one on the bottom is for two speed travel. Cap the medium size hose on the top and put another hose on the fitting of the motor and run it into a bucket. Then stall the track and see how much oil you get out of it. The motor is attached to the final and it looks like the final has to come out of the track frame. I don't remember the motor having to be removed from the final drive by tearing down it all down. I seem to remember a couple of allen bolts that hold the motor to the gear drive.
Thanks John. As you describe it that's the way i first thought. The directional flow must be handled up at the main valve body. I saw the Allen bolts but I believe access is partially blocked by the housing. I'll look closer when I go up the hill again in a couple of days. And you think the two-speed travel is controlled by the smaller ~1/2" line? I thought that was a brake, thus my confusion. And after reading a bit more on pressure checks in the shop manual I read that relief pressure is adjusted at the control valve body group, correct?
The travel brake works when flow is provided by the direction hoses. It is automatic. The reliefs for travel are in the motors. Direction is controlled by the spools in the main control valve. The main reliefs are in the control valves.
As always, thanks again John. The shop manual doesn't provide a ready overview of the motor operation, at least I haven't found one yet. I've been trying to glean more insight by studying the specifications and pressure adjustments. Plenty of information should i have to tear it down, though I think I'd be either looking for a replacement or having ours rebuilt. So if reliefs for travel are in the motors does the bypass fluid run into the case and drains? Might this be the cause of the case drain lines jumping when travel is initiated? And is the two-speed activation controlled by pilot pressure being applied or cut by the two-speed solenoid valve? We DO have that and all other solenoids assigned to separate switches. We have to do some testing first and your expert help along the way has been golden for us. Identifying the apparent bypass through the case drain lines will be key. -Tom
When pilot pressure is applied to the 2-speed port on the motor does that shift speed from low to high or vice versa? -Tom
All fittings are JIS, not JIC.
Applying pilot pressure puts the motor in high range. I seem to recall that Link-Belt used BSPP fittings on the hydraulic hoses.
My hydraulic house thought JIS. I picked up caps and plugs in three sizes for testing. If you're correct I might be foiled until I pick up yet another fitting type. Thanks John, and we've always been switching the two-speed solenoid on and apparently putting the drive in high while the tracks are somewhat partially buried in dirt and dried mud from almost 10 years of being parked. I plan to do the case drain test once I'm able to cap the drain hose end. I also want to first try raising one track, then the other with the boom to see if I get any track movement. I keep getting closer bit by bit in understanding this machine thanks to your wisdom and experience. Thank you! -Tom
I believe they are BSPP I believe that when the motor goes into relief it exhausts through the opposite line as it would be retuning drive oil to tank sounds like you have to much case drain the only way you get case drain is by the pistons leaking past the swash plate. check case drains I believe you will have a excessive amount
Thanks Dave. Per Tom C's mention of BSPP fittings I looked at my german built compactor and see that it also uses BSPP fittings. I believe the pilot lines are JIS as we've had to replace a few and they're flare like JIC. I'm going to see if I can round up some 6 and 8 BSPP caps locally tomorrow. If not if not I'll have to order online. I see them listed as 4028-6 and -8 which I'm guessing is the industry numbering. -Tom
By any chance do you know if the motor will come out without having to pull the final drive assembly? I'm hoping that we don't have to get into pulling tracks. Since we've rewired the machine to run in bypass mode I now realize that we've been trying to move the machine in high gear when the tracks are pretty well mired in sand and dried mud from many years of being parked. I'm going to try lifting the machine on each side with the two-speed solenoid off which should keep us in low speed and try travel on each side first. If no travel or track movement I'll then do the case drain test when I have the BSPP caps in hand. Thanks again! -Tom
If the shift pistons are leaking by, the motor will be stuck in high. You should check the fittings to be sure of what is there. The fitting is likely a British Ball Nose.
You were right again about the fittings being BSPP ball nose, so I went up yesterday armed with caps and plugs in 1/2" (-6), 5/8" (-8), and 11/6" (-12) to do some testing as follows: 1) We fired the beast up and let it warm for about 10 minutes. We used the boom to raise each track off the ground to see if we could get any motion. None. We did not have the two-speed solenoid valve activated so there was no pilot pressure going to the track motors, thus should have been in low speed. 2) In watching the case drain hoses when travel was initiated there was considerable "jump" suggesting excess case drain when travel is initiated. This same jump was observed with the tracks off the ground and free. 3) All functions (boom, arm, bucket, swing) worked nicely proving that we have good pressure from P1 and P2 pump sections which also power travel motors left and right. 4) I pulled the case drain line off one motor and capped the case drain line going to the tank via the rotary joint (which had been resealed in 2011 by a reputable shop). I had a hose connected to the drain port on the motor going into a bucket and had my partner fire the machine up. With no control inputs and the engine at idle I had a gush of fluid coming out the drain port at what I would estimate to be between 2 and 5 gpm. I'm certain that if we had engaged travel that we would have blasted my test hose off with even higher flow. We immediately shut down. 5) Since we had no pilot pressure going to the motor and the case drain hose disconnected and capped, the only hoses going to the travel motor are the two 11/16" lines coming from the control valve. So it would seem certain that there is a bad seal or other element in the motors that is allowing pump pressure to leak past the control valves and into the motors themselves. If my conclusion at this point seems to be logical the next step would be to either try to source a couple of good motors, or have ours repaired/resealed. The motors DO appear to be secured with at least three allen head bolts to the final drive, so we likely won't have to pull a track as feared. I'll study the parts book section to confirm. Any other thoughts and opinions are MOST welcome at this point! Thanks folks, -Tom
At this point you should check if the travel spools are still in the main control valve. But know that even with spools in neutral theres still pressure in the main lines,bucket, lifting, arm ,swing and travel, but not enough to mobilize then until the spool are shifted. If you loosen your boom in and out hoses going to ram,you'd still see a substantial amount of oil gushing when you start the machine. In my opinion, with spools in neutral and case drain looks like a fountain, the bypass in there is much. You'd eventually loose it to visually inspect the state of the barrel and pressure plate.
What's had us confounded is that both motors exhibit the same failure despite the machine having been moved to its present location in 20011 when the rotary joint was removed and resealed. I'm leaning into the theory that we have valves/spools somewhat stuck from the long period of no operation.