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Dan, Technician
Category: Agriculture and Farm Equipment
Satisfied Customers: 5437
Experience:  17+ yrs. shop and field experience with all major brands of heavy equipment, trucks and farm equipment - 1995 WyoTech graduate.
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To JCB team member, We have a 412S Series 3 backhoe that

Customer Question

To JCB team member,
We have a 412S Series 3 backhoe that is having trouble shifting gears. Gears are not slipping, they just do not want to seem to engage. We replaced a gasket connecting the the solenoids to the transmission thinking there was a leak causing transmission fluid to skip/jump to another channel when gears shifted. When we replaced it everything worked well for a short period, but the backhoe is starting to not react again when shifting. It seems a relay or possibly one or all solenoids (3) are bad? Please help us diagnose. Thank you.
Willcox, AZ
Submitted: 1 year ago.
Category: Agriculture and Farm Equipment
Expert:  Dan replied 1 year ago.
Hi Levi, My name is***** will be glad to try to help. First what is your serial number? The most common cause of no shift is a faulty shift controller. Test for 12V to the solenoids in each gear position to confirm and tes power in and out of the shift controller. If ok then test the resistance of all solenoids to see is they are all within the same resistance range. Also apply power/ground to do a click test on the solenoids and verify they are mechanically working as well. It is highly unlikely you have 3 bad solenoids. Let me know
Customer: replied 1 year ago.
shift controller is fine. First thing we checked yesterday. Yes, we have tried all of the above prior to response. Resistance was fine and all solenoids worked in conjunction with the shift controller. We took the wiring harness off to double check for any shorts. It was fine. It will still move forward even without the wiring harness attached, which presumed it should be in neutral when no harness connects solenoids to send relays.
It appears when we get it to move (w/ harness) it starts to slowly lock up within 5 minutes of moving through the gears. Possibly valve body issues even with good solenoids?Side note: Transmission does not slip or grind. It does however warms up quicker than it should. We've changed fluids and filters obviously and dissected the old filter to see if we have any flakes. It was fine, so internally transmission is not the issue, but why it warms quickly is baffling.
Expert:  Dan replied 1 year ago.
4 speed or 6 speed powershift? 2wd or 4wd model?
Expert:  Dan replied 1 year ago.
Have you tested your pressures yet?
Expert:  Dan replied 1 year ago.
I Log on in between jobs and nights as available. We can post back and forth as needed. I do not normally do this but under the circumstances i am going to hook you up with all your service and test info. See PDF pages 570 and on as well as 600 on. I recommend running though your pressure checks if you have not already.Troubleshooting/Repair
Customer: replied 1 year ago.
Dan,Thanks for working with us. We'll work through that this evening. Here is the Serial #: SLP214ESTE0447822
It is 4WD, 4 speed, power shift.
Expert:  Dan replied 1 year ago.
Thanks for the info.... all the pressure and electrical test info is in the link i posted. Let me know the actual pressures and results of the testing.
Customer: replied 1 year ago.
Will do
Expert:  Dan replied 1 year ago.
Pleasure to help
Customer: replied 1 year ago.
If pressure is to high or to low, what does that say. Manual says a pump could be bad or a strainer.Also, reading more into Torque Converter troubleshooting we're seeing similar problems.
Expert:  Dan replied 1 year ago.
Yes, Low pressure could mean a plugged suction strainer that feeds the pump or a faulty pump. Torque converter will also cause low pressure if leaking internally and the converter is slipping. That is a fluid coupling acting as you clutch. The pressure tests and then compared to specs will isolate the problem area.
Customer: replied 1 year ago.
I could be blind and its in my face but I do not see what the specs are when looking at the pressure tests some do not now what to use for comparison. Just how to do it.Also my pages may be different but pgs 670 & 700 do not show anything relavent. Pages such as 13-1, 63-3 etc are easier to find.
Customer: replied 1 year ago.
Also, one thing that makes us hesitant on pressure checks is that gears aren't slipping as if the pump is bad or out. The machine either most times won't rev up all the way to higher RPMS, as well as when put in reverse it will fight with itself and try and go forward or lock up. It also will not slide into neutral but locks up. I'm guessing if pressure is low it should role in nuetral fine, yes?The other red flag as mentioned before. - transmission warms up very quickly and higher temp than normal.
Expert:  Dan replied 1 year ago.
Hi, I was on the road today.I help on here part time in between jobs. It is a PDF file and I use the page numbers for the PDF file at the top of the screen instead of the document pages... also I referred PDF pages 570 and 600 on for test information. You need to test your pressures. I have been a technician a very long time and rebuilt transmissions on tractors, loaders, trucks, dozers, etc. Worked for Cat, Komatsu, Deere, Volvo, and JCB dealers in the past. The first thing you will lose is lube which is everything left over for pressure and is non adjustable.... Lube helps lubricate and also cool the transmission so therefore if you lose that flow of lube from a weak pump you can still not slip but start to overheat and that is when failure will start to take place. It is important to see what your pressures are for your pump, each clutch, and lube. If pressure is low in one clutch but good in the rest it isolates a leaking clutch. If pressure is low in all speeds it is a pump issue..... Let me know what you have for pressures.
Customer: replied 1 year ago.
I must be overlooking.... I have searched and searched the manual and cannot find the proper pressures to know what is the correct limit for any tests. It only shows where to check and the broad range of pressure so to have the correct pressure gauge. Many times it states to check "technical data" for readings, which is section C, which I cannot find anything.
Expert:  Dan replied 1 year ago.
Go to section 6-1 which is "PDF" page 562 you will find what I posted below in the proper format since it pasted a bit scrambled. Powershift Gearbox - 4 SpeedDescription Full electro-hydraulic transmission unit with input, reverse,layshaft, mainshaft and*****clutch packs giving 4forward and 4 reverse speeds.Designation PS764 (4 wheel drive)Weight (dry)2WD T.B.A.4WD T.B.A.Gear Ratios1st 7.97:12nd 4.29:13rd 1.86:14th 1.00:1Torque ConverterTorque Converter Dia. 310 mm (12.2 in.)Torque Converter Identification 04/600580 04/600581Torque Multiplication at Stall 2.52:1 3.01:1Converter Pressures (in neutral) bar kgf/cm2 lbf/in2Converter In at 50 ºC 1000 rev/min 2.0 - 4.95 2.0 - 5.0 29 - 722000 rev/min 4.0 - 6.8 4.1 - 6.9 58 - 99Converter Out at 50 ºC 1000 rev/min 0.6 - 2.25 0.6 - 2.3 8.7 - 332000 rev/min 1.25 - 2.50 1.3 - 2.6 18 - 36Converter Inlet Relief Valve Pressure (max.) 7.1 7.2 103Lubrication Pressures (in neutral)At 50 ºC 1000 rev/min 0.25 - 1.0 0.26 - 1.0 3.6 - 14.52000 rev/min 0.50 - 1.0 0.51 - 1.0 7.3 - 14.5Main Line Pressure (in neutral)At 50 ºC 1000 rev/min 11.4 - 15.7 11.6 - 16.0 165 -(###) ###-####rev/min 12.4 - 17.0 12.6 - 17.3 180 - 246Flow Rates (in neutral) L/min US gal/min UK gal/minCooler at 50 ºC 1000 rev/min 14.0 MIN 3.7 MIN 3.1 MIN2000 rev/min 17.0 MIN 4.5 MIN 3.7 MINPump at 50 ºC 1000 rev/min 16.0 MIN 4.2 MIN 3.5 MIN2000 rev/min 34.0 MIN 9.0 MIN 7.5 MINControl Solenoid Valves 3 way, 2 position, normally closed, integral suppression diode.Coil Resistance 7.5 Ohm @ 20 ºC
Expert:  Dan replied 1 year ago.
Section F is your pressure specs..... C is your electrical testing.
Expert:  Dan replied 1 year ago.
Hi Levi, Did you get this resolved? Please remember to rate as that is how the site credits the experts for their time helping on the site.
Customer: replied 1 year ago.
Sorry. Thought I had answered and then realized I was mid text and never hit send.
We didn't do a pressures test. We took a few steps back. We got under the relays and noticed the wiring was all kinds of jacked. Wires had been spliced, burnt and put in the wrong places. We fixed that somewhat which it helped, but problems still occurred. We've had enough. We just put it up for sale and let it be someone else's headache.
Expert:  Dan replied 1 year ago.
Thanks for the update. Please take a few moments to rate my service as I took time to help you. The experts only get credit for their time from the site on positive feedback and accepted answers. It has been a pleasure working with you on this.