2003 Caterpillar 160H worst luck tranny issues

[zx240lc-3]

Hi Guys/Gals,

Background story:

Bought a 2003 Caterpillar 160H Grader with 11,000hrs it is a fairly clean unit and has a major work order for a replacement longblock and few other misc items. Before we put it into service we had our in house mechanics check it over and found that there was coolant mixing with the transmission fluid. We diagnosed the issue as a bad cooler and replaced that without issue, flushed the trans and coolant system a couple times and put it out to work. we put about 250-300hrs on it and started running into transmission troubles . The operator was complaining that it would drop out gears when articulating one direction but not with everything straight. He had also noticed that the inching clutch was at the top of its stroke. He was able to work it for about another 20hrs fine without articulating to finish up the project and then it was returned to our shop. He said anytime the machine did cut out he would just stop for a while, shut the master switch off and then it would come back on again and all gears would work.

This is when everything started getting messy.

I hoped in the machine and drove it around, nothing seemed to be the matter with it even articulating the machine it was 100% fine. However the inching pedal was at the top of the stroke only the last 1/8th of pedal play would engage the gear. We do not have the Cat ET software so I hired a mechanic to come calibrate the clutch. He did and said everything seemed good. I went to pull it out of the shop and we all of a sudden have no reverse gears at all but full engagement of all forward gears. We check all the wiring at the back and seems like we are getting solenoids engaging when they shouldn't be. OK MUST BE WIRING. check the harness from ECM to back, everythings good no cross continuity or broken wires. Check the sub harness and nothing everything is good. Get the mechanic with CAT ET software back and as we have an active code now. The codes coming up are both output speed sensors. He also says everything in the shifter is good(verified CAT ET shows it going thru all gears) but there is an intermittent break in solenoid #5 wire from ECU to solenoid. He tells us we have full pressure at all the solenoids but since its not going anywhere it must be worn out clutches.

We purchase the CAT service manual and pull the trans out, go through the clutch packs and sure enough the rear clutches are burned right out. Follow all the instructions, everything goes smooth and we get the transmission back together and in the machine. Go to drive the machine out of the shop and it goes in forward fine, reverse has only a couple gears. Drive it around some more and then soon enough we have NO GEARS AT ALL. Push it back in the shop and call the local CAT dealer. Thinking it maybe the ECM now. They come out install a test ECM and are able to drive it in some gears but not all, says its intermittent but not the ECM, must be something we've done in the tranny(they obviously want the work and don't put much effort into helping us figure out whats wrong, just tell us to drop it off and they will fix it). He also said that our serial number group falls into a range that has had issues with the manifold on the side of the trans cracking internally and that we should inspect that.

We take apart the manifold and find nothing. Drive it out of the shop have somewhat 1st gear, somewhat 2nd gear, then nothing, some reverse gears work fully and some don't work at all. then no gears at all and we have to push it back into the shop. We decided to replace the wiring harness from ECM to solenoids and that is how it sits. Still doesn't pickup any gear and still has the error code for the output speed sensors.

Not sure what to think, it must be something inside the trans but its hard to believe as the gears sometimes work great and other times don't work at all. Does anyone here have good knowledge of the inner workings of the transmissions on these machines? I'd like to know if there is something that could be sticking or bypassing oil that is causing the issue. Its hard to justify paying the Cat dealer 40k + for a transmission rebuild. I am not even sure if they do this if it will even fix the issue. I think it could be something else completely as our problem has never really gone away. I am thinking the reverse clutches have been worn out because of half engagement at times.

Sorry for the long post. this has been dragging out a couple months now and its getting hard to remember but I should be able to answer any questions.

S/N: ASD00346

 

[Mark250]

hi, zx240lc with the inching pedal engaging at the end of stroke sounds like the position sensor is not working or not calibrated ,and the machine is operating on the inching pedal limit switch but I thought it would through a code for that.
can you confirm that the speed sensor connectors have not been interchanged as they are 90 degrees out of phase to each other
Have you verified transmission pressures in each range. have you checked pressures with diff lock isolated

Mark

 

[zx240lc-3]

Mark250:

Could you explain to me what you mean by isolate the diff lock?

I have verified the wire numbers and the output speed sensors connectors they have not been swapped. I will agree with you that it does seem like there is an issue with the inching peddle however it does still calibrate, we've tried this twice since re-installing the transmission and there is no code. How does this system work? I understand that the ECM uses PWM to control Fwd 1-3 gears, does the ECM just calculate what the inching pedal is seeing for voltage and accommodate? or is there a solenoid that actuates a spool instead of the cable on an old style machine?

I will check pressures again and get back with you, please verify how to isolate the diff lock. Originally we had full pressure on all gears, the CAT dealer told us we have no pressure on the 1st gear clutch pack, he figured a piston was over stroked because the clutches were worn on that gear but I never actually seen him test that.

 

[Mark250]

hi,the diff lock valve uses transmission oil to operate, to eliminate it being the cause of low pressure in system remove hose from diff lock valve and cap. the inching position sensor sends a PWM signal to the ECM ,the ECM controls current and hence hydraulic pressure to the direction clutch's (simplified explanation if you need more info I can email to you)
have you checked the clutch mechanical linkage for adjustment and correct operation
you could disconnect the position sensor and operate in this condition .this will force the ECM to use the limit switch as a valid signal
if you have low pressure it is possible you have broken the counter shaft seal rings. if you confirm low pressure you could remove the counter shaft end cover to check
Mark

 

[Nige]

More questions I'm afraid.......and in no particular order.

1. Was a full pressure test of the transmission done before you removed it the first time and if so what were the results..? "Full pressure" is no good, it needs to be a psi value for each clutch to be of any use to us to help you diagnose this thing.
2. What was the condition of the park brake discs like when you stripped the transmission..?
3. Have you closely examined the condition of the main machine wiring harness where it crosses the articulation hitch..? (A known problem area).
4. You say you have a shop manual. Does it have an electrical schematic..?
5. Has the resistance of each of the solenoids for the transmision clutches been measured..? (The spec is on the electrical schematic, can't remember off -hand what it is)
6. Since the problems with the rebuilt transmission has anyone removed the suction screen to look for clutch debris in the screen..? That is assuming the screen was cleaned at the time the transmission was rebuilt.
7. Did you rebuild all the clutches in the transmission when you had it out or just the burned-out ones..?

Usually what happens when a transmission clutch wears the piston gets to a point where it has so much travel that it pops out of the housing and tears up the piston seal in the process. At that point the affected clutch will register no pressure whatsoever.

 

[Nige]

Another thought just struck me reading your OP. Coolant in the transmission fluid can adversely affect clutch disc friction material - it peels off the backing plate after a while. Even though you replaced the cooler and flushed the damage may have already been done. This makes the qestion regarding whether you renewed the friction discs (and the clutch piston seals) in all the clutches or just the two that burned up..?

As a suggestion when assembling a transmission it's an idea to rig up an air line and pressure test each clutch after it's been assembled. It saves potential red faces later .......

 

[zx240lc-3]

Nige thanks for the reply.

More questions I'm afraid.......and in no particular order.

1. Was a full pressure test of the transmission done before you removed it the first time and if so what were the results..? "Full pressure" is no good, it needs to be a psi value for each clutch to be of any use to us to help you diagnose this thing.

i believe it was 350psi at all the pressure test ports on the manifold on the transmission.

2. What was the condition of the park brake discs like when you stripped the transmission..?

That i am not sure of. How does this work where it would effect us getting no gears? the park break does still function.

3. Have you closely examined the condition of the main machine wiring harness where it crosses the articulation hitch..? (A known problem area).

Yes, we pulled the harness from the machine to inspect it, originally everyone had thought this was an electrical issue but everything except for 1 wire was checking out correctly. We figured there would be no way to be 100% that it wasn't the harness without replacing it so we ordered a new one from Cat and installed it, the harness is now brand new and has not resolved our issue.


4. You say you have a shop manual. Does it have an electrical schematic..?

Yes it does.

5. Has the resistance of each of the solenoids for the transmision clutches been measured..? (The spec is on the electrical schematic, can't remember off -hand what it is)

We have tested the coils, i believe the value was 32 ohms and everything tested good.


6. Since the problems with the rebuilt transmission has anyone removed the suction screen to look for clutch debris in the screen..? That is assuming the screen was cleaned at the time the transmission was rebuilt.

Yes and it was clean. it was clean when we removed the trans however and it was replaced during rebuild because the magnetic part of it had came unglued.


7. Did you rebuild all the clutches in the transmission when you had it out or just the burned-out ones..?

only the burned out clutches.

Usually what happens when a transmission clutch wears the piston gets to a point where it has so much travel that it pops out of the housing and tears up the piston seal in the process. At that point the affected clutch will register no pressure whatsoever.

Another thought just struck me reading your OP. Coolant in the transmission fluid can adversely affect clutch disc friction material - it peels off the backing plate after a while. Even though you replaced the cooler and flushed the damage may have already been done. This makes the qestion regarding whether you renewed the friction discs (and the clutch piston seals) in all the clutches or just the two that burned up..?

As a suggestion when assembling a transmission it's an idea to rig up an air line and pressure test each clutch after it's been assembled. It saves potential red faces later .......

We have only replaced the worn clutches, these were in the reverse pack. We have very positive engagement in the forward gears when it was working before trans rebuild. We could stall the machine out while holding the brakes with it in gear. I just spoke with our mechanic that did the job, he said on the first start up after the rebuild the machine would not move at all. After we tried it a few times if you were sitting in gear(reverse at the time) it would eventually grab and have good engagement where you could stall the machine out with the brakes. We were able to get it outside and drive it around the yard in both forward and reverse. then it would stop doing that, then it would come back, then it would stop, now it does nothing but perhaps if we tried for long enough it would start moving again?

We have tried air testing the spools (behind triangle covers at the rear of trans) and get good engagement of all the clutches, you can hear it lock in fairly loud. We will be doing a few pressure tests today and I will post back with results.

 

[Nige]

The reason I asked about the park brake is because it's inside the transmission and a brake failure is pretty much guaranteed to result in a transmission clutch (or clutches) failure. A bit late now but to me it's false economy not to at least replace all eight clutch piston seals when you go into a transmission, whatever the clutch discs look like.

Regarding clutch pressures, refer to the chart in the T&A section of the manual. Depending on which gear is engaged the spec varies from 225psi up to 390psi. So to say the pressures were "all around 350psi" is quite frankly ridiculous.

Similarly the solenoid resistance. You have 5 that are specced at a 31.3 +/- 3 ohms and the other three that are 8.7 +/- 0.4 ohms. Again they can't all be 32 ohms.....

Have you tried switching the complete solenoid valve for reverse to either fwd high or fwd low which IIRC are the other two identical valves (parts manual will confirm that) and see if the problem moves from reverse to the forward direction..?

It may be well worth checking in the electrical schematic if there is a diode in the control circuit for the diff lock solenoid valve. There was a case on here not so long ago where a failed diode caused all sorts of weird transmission shifting issues. It may be referred to as an arc suppressor in the schematic.

I'll hav a bit of a deeper dig later but I'm working from a smart phone and somewhat limited in what I can achieve.

 

[zx240lc-3]

I've checked the resistance of the solenoids and we have 34ohms for the 5 - 24volt solenoids. 9ohms for the 3 PWM solenoids.

I've attached the chart we did for clutch pressures at the test ports on the control valve that is located on the side of the transmission. It does not look good, perhaps you can shed some further light on what is happening.

Charge pressure at the filter head was 420psi. Most of the pressures at the test ports are not in spec. Most are low on pressure and 1 is high(port 4). the only ports that are in spec are 8,9 and 10.

When doing the test we had the machine at 2000rpm. I had the machine go into gear after about 20seconds of waiting while we watched the pressure. When it goes into gear the light on the dash for the error code will go out. This happens in 2nd gear FWD and 1st gear REV, but never 1st gear FWD. It does this consistently each time we stopped the machine to swap ports.

https://i.imgsafe.org/eb378b1f68.jpg

https://i.imgsafe.org/eb37db8f0e.jpg

 

[Nige]

Did you do the tests by disconnecting the drive shaft as per procedure or raising the machine off the ground and blocking the tandems up so the rear wheels can spin..?
You mentioned changing the gauges. You did use 3 gauges as per the procedure, correct..? Actually the best way is to use 8 gauges and hook all the test points up in one hit, but not too many shops can scrounge up 8 x 0-500psi gauges at the same time. High Idle for that engine is 2000RPM so you were doing the tests at the correct RPM.

What your pressure tests tell me ........

1. You have no pressure at all in clutch pack #1 (Test Point 5). This clutch is used for the following transmission speeds - 1st, 4th, 5th, 7th, & 8th forward.
2. The pressure in clutch pack #3 (Test Point 3) is only about 50% of what it should be. This is the reverse clutch.
3. The pressure in clutch pack #6 (Test Point 6) is about 100psi low. This clutch is used for 1st & 5th forward plus 1st & 4th reverse.
4. The pressure in clutch pack #2 (Test Point 7) is about 120psi low. This clutch is used for 2nd, 3rd, & 6th forward.
5. The pressure in clutches 4, 5, 7, & 8 is within spec.

To engage any speed in that particular transmission requires 3 clutches to be engaged - 1 direction clutch (Fwd or Rev), 1 speed clutch (1, 2, or 3), & 1 range clutch (Hi or Lo). Here's the clutch table -
1F - 1 6 7
2F - 2 4 7
3F - 2 5 7
4F - 1 5 7
5F - 1 6 8
6F - 2 4 8
7F - 1 4 8
8F - 1 5 8
1R - 3 6 7
2R - 3 4 7
3R - 3 5 7
4R - 3 6 8
5R - 3 4 8
6R - 3 5 8

So based on those numbers (0psi in clutch #1) there's no wonder you are getting no 1st gear forward. 120psi low on clutch #2 will give problems with 2nd speed forward, & combined low pressures in clutches #3 & #6 will give problems with 1st speed reverse.

Did you by any chance take a look inside the transmission pump in the course of the first transmission teardown..? if there were handfuls of clutch friction material kicking around I wouldn't be surprised if it was toast.

Try Mark's suggestion of physically plugging the hydraulic line to the differential lock valve to ensure that you are not losing flow via leakage at that point, and repeat the clutch pressure tests. If nothing changes my next suggestion would be pull the pump apart, and I hate to be the bearer of bad tidings but my suspicion is that although you have rebuilt a couple of clutches inside the transmission you've missed something in a number of clutches that's resulting in major internal leakage. Hence my earlier comment to reseal all eight clutch pistons every time a transmission is pulled apart, even if the friction discs are not replaced.

 

[Raildudes dad]

Nige:

I read everyone of your posts. I continue to be totally amazed by your knowledge and your willingness to share it with us. Thank you for sharing

Raildudes dad

 

[Nige]

Before I forget, here's the arc suppressor (diode) that's wired in parallel to the diff unlock solenoid valve. Make a point of checking both the diode and the solenoid (spec is 32.6 ohms +/- 1.6), even if it's just to rule it out. Note that the solenoid valve is to unlock the diff so it activates ass-backwards to what you might expect.......if the solenoid valve is not working the diff is permanently locked.
Hint: There is another arc suppressor on the machine of exactly the same Part # wired in parallel to the A/C compressor clutch .........

 

[Cmark]

Have you or anyone had the control valve apart? Inside the clutch control spools are orifices which don't take kindly to contamination. They look like an anodised aluminium slug in various different colours. If they get blocked, the spool will stop working and it's almost impossible to clean them out. I usually replace them as a matter of course on a transmission rebuild.

 

[Nige]

Good point CM. You tend to assume when there has been a failure that everything has been cleaned out.

Take a look in your parts manual at 179-6063 Valve Gp and make sure that the 6I-9395 Screen Gp (Item 22) is not blocked.
You'll find the orifices for your transmission S/N JRR00635 shown in both the 184-1130 (Fwd, Rev, & Range Clutches) and 184-1132 (Speed Clutch) Valve Gps.

 

[zx240lc-3]

OK guys here's a bit of an update.

We pulled the control valve off the side of the transmission. Went through everything again and we replaced the orifice "bullets" and found that one of the solenoids was sticking intermittently so we replaced that as well. Now we have forward gears 1,2,3,4 and reverse gears 1,2,3.

We are going to do a pressure test later today if we get a chance to see if anything has changed. I'll let you guys know. I think it maybe a problem with the solenoids even though they are testing OK they maybe still not doing there job. Any thoughts?

 

[Nige]

If the solenoid resistances are checking out OK don't rule out the possibility that one or more of the actual valves themselves apart from the one you replaced could be sticking intermittently. This is indeed possible if there have been large amounts of contamination flying around the system. Moving identical valves around the various stations where they are used could isolate which one is the culprit.

 

[zx240lc-3]

If the solenoid resistances are checking out OK don't rule out the possibility that one or more of the actual valves themselves apart from the one you replaced could be sticking intermittently. This is indeed possible if there have been large amounts of contamination flying around the system. Moving identical valves around the various stations where they are used could isolate which one is the culprit.

Good news! We have the grader shifting all the gears now. Yesterday we pop'd the driveshaft back on and took it for a drive. We had all the gears but 2,3,6 forward working. We saw that they all shared a common solenoid and decided to order a replacement complete with valve assembly. Installed it this morning and now it will go through all the gears without issue. Just needs to be calibrated and we should be back in business.

I do believe this was our problem all along and what originally caused the clutches to wear out. It must have been contamination causing an issue with a couple of the valves. Thank you all very much for the helpful responses! We've learned a lot about these graders in the process.

 

[Nige]

If you are using Cat filters for the transmission I'll give you another suggestion. You can go up a level in filtration but to do it you need to replace the 2 springs in the filter bypass spool. If contamination was your issue all along then better filtration gives you a fighting chance of it not coming back.

The new arrangement was used on 160H from S/N ASD00556-Up, slightly newer than your machine.

The 328-3655 filter element replaces the 1R-1809 that was originally used in that location.
The new springs are Part Numbers 334-2679 & 334-2680 - 1 of each. They are set to pop off at a higher pressure to best utilize the higher efficiency of the new filter element. Discard the existing springs and fit the new ones at the same time as you are doing a filter change and it takes about 5 minutes to do the upgrade.

If you want the factory documentation regarding the upgrade then drop me a PM with your email address and I'll gladly send you a copy.

 

[zx240lc-3]

OK, so back to having issues!!

We had someone come out and do the calibrations. When he arrived and started running the machine there was once again no 2nd,3rd,6th gear working. We had replaced the solenoid as indicated the other day and was able to get the machine shifting all the gears but for whatever reason having it sit for a couple days while we waited for him to show up they dropped out again. He was able to get the machine up to operating temperature and performed the calibration for the PWM solenoids, he said that the circuit for the #2 solenoid(the one that is common to 2nd,3rd, and 6th) was low on pressure but he was able to turn it up and get it within spec. Everything at this point seemed good, the machine passed calibration without any codes and he went on his way. We moved the machine out of the shop the next day and everything was good. it got parked outside and we waited for it to go out to the next job. A couple days later we needed the machine and when we went to use it nothing on 2nd,3rd and 6th again. ARGGGH this is getting ridiculous. Since the last time we did the solenoids and having only 1 PWM still not replaced we decided to go ahead and replace the last one. Had it in the shop, poped the new solenoid in and then took it for a test drive. We had it working slightly but not fully engaging like we thought it should, it hesitated for a moment but then eventually grabbed. Try it some more and then we have nothing again and that's how it sits.

Reading thought the manual RENR4104 page 207 there is a procedure for initial pressures. This has never been done and we are wondering if doing this could help our situation. I have a couple questions about the procedure though and wondering if someone with experience could help clarify.

What is the purpose of installing 139-7050?

In regards to the final note "note: If the transmission clutch pressure is out of the tolerance range, most likely cause of failure will be a failed modulating spring, debris in the control valve or a seal failure within the transmission." is there any way to narrow down which of the 3 will be causing our issue?

Right now we have 0 pressure on the test port that corresponds with solenoid #2.

Thanks again guys! hope to get this sorted out sooner or later.

 

[Cmark]

Quick and dirty way to find out if you have leakage in a clutch pack or sealing ring;

Work out which countershaft has the suspect clutch.
Remove the triangular cover over the end of the relevant countershaft.
Undo the bolts which hold the seal carrier to the end of the shaft and pull it out.
Inspect the seal carrier, seals, and the bore in the casing where the seals run for obvious damage. Also check the O rings where the carrier mates to the countershaft.
Get an air blow gun with a long nozzle and rubber cone tip. Shove it up the hole in the casing and apply air pressure to the holes in the countershaft. One hole will be for lube oil and won't build pressure. You should be able to hear the clutch packs snap shut when you apply air pressure to them.

If this all checks out OK, you can concentrate your efforts on the control valve.