Jinma 254 front differential rebuild

Forum Forums Tractor Operation And Maintenance Jinma 254 front differential rebuild

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    • #49654
      DemocracyNow
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        This is my second time having to pay a lifetime fee to be a CTOA member in the last 20 years.But the price is reasonable and I wanted tractor owners to have info I didn’t.

        My Farmpro 254 Jimna front differential failed after 1200 hours of near continuous use.I searched the Internet for info with No results on the differential itself.

        My midline transfer driveshaft would engage but no front wheel drive.Both front wheels freewheeled  independently.

        I jacked the tractor front end and removed the left and right drive hubs.The drive gear #184-31-119 on the driver’s right front driveshaft was chewed and with minimum engagement.The gear it engaged with looked fine.Metal shards littered that area.Ordered replacements from Affordable.

        Removed both front driveshafts and housings.I removed four bolts holding front differential and lowered it.Midline transfer driveshaft disengaged from case as it was lowered.I did remove FEL cross brace but may not have had to.

        Removed differential case cover and found four gears inside .The two planet gears (184-31-183 were chewed and worn about 1/8” into the gear housing on both gears.The brass Belville washeres that should have protected the housing all four gears were mounted in were nowhere to be found.They were probably never installed at the factory. That created lots of slop and disengagement with the 184-31-187 axle driveshaft gears they meshed with.Both the 184-31-187 gears were worn but not chewed.Ordered gears and washers from Affordable.I received the brass Belville washers but the other thrush washers Affordable send were nylon?Hope they last.BTW the brass washer pair under the forward mounted 184-31-187 gear was reusable ….but not found in any exploded parts views.Go figure?

        Hope I set the lash correctness,which is .5MM.I did move the left bearing race tube on the large bevel gear side into the pinion gear to achieve that .5MM (.019”)lash and then moved the right bearing race tube in to remove all but .010 thousands clearance on the whole gear housing assembly as it rotates between both left and right bearing races.Done by feel.Hopefully the pictures will help.

      • #49655
        DemocracyNow
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          Jinma 254 front differential lash adjustment and gear engagement pattern.

        • #49656
          DemocracyNow
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            Gear assembly

          • #49657
            DemocracyNow
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              Planet gear(2) with Belville brass washers

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            • #49659
              DemocracyNow
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                Gears 184-31-187 that power left and right wheel axles.

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              • #49661
                DemocracyNow
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                  Differential case with damaged components.

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                • #49663
                  DemocracyNow
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                    Dropping differential case .Midline driveshaft disengaged with balls as unit was lowered.Reinstallation was simply reverse of that.

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                  • #49665
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                      Removing bearing race adjustment tube.Capture in case with Oring and locking collar.Remove collar and use a puller.Tubes would not pry out .but puller lifted them easily.

                    • #49666
                      DemocracyNow
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                        Sorry but half my photos are not uploading.Any suggestions?

                      • #49667
                        DemocracyNow
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                          Locking tabs keep bearing race tube locking/adjustment rings from movement.

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                        • #49669
                          DemocracyNow
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                            Wear mark pattern after 30+ revolutions.Used spray paint.Reused original brass shims on pinion mounting so pinion maintained original position as it meshed with large bevel gear.

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                          • #49671
                            DemocracyNow
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                              Pinion mount with shims

                            • #49672
                              DemocracyNow
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                                You will need a bearing separator .

                              • #49673
                                DavidPrivett
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                                  looks like you are putting more care in assembly than the manf. did for sure.

                                • #49675
                                  DemocracyNow
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                                    Planetary gear cluster without larg ring gear and left facing side gear

                                  • #49676
                                    DemocracyNow
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                                      Large ring gear and left side gear

                                    • #49747
                                      DemocracyNow
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                                        This date 1/17/2022 photo file transfer attempt using new iPhone 12

                                         

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                                      • #49749
                                        DemocracyNow
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                                          Wow  !my new iPhone 12 managed a photo transfer. Let’s try another.

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                                        • #49751
                                          DemocracyNow
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                                            Entire assembly viewed from left front.

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                                            • #49755
                                              DemocracyNow
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                                                Correction: view from right front

                                            • #49753
                                              DemocracyNow
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                                                Pinion gear and spacers

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                                              • #49756
                                                DemocracyNow
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                                                  Empty case

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                                                • #49758
                                                  DemocracyNow
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                                                    Gear cluster without outer bearings and adjustable locking rings

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                                                  • #49760
                                                    DemocracyNow
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                                                      Adjustable locking rings holding gear cluster. Pinion gear and housing removed from case.

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                                                    • #49762
                                                      DemocracyNow
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                                                        Large/8” bearing remover

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                                                      • #49764
                                                        DemocracyNow
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                                                          Differential case with damaged components.

                                                        • #49765
                                                          DemocracyNow
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                                                          • #49767
                                                            DemocracyNow
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                                                              Left front view
                                                            • #49768
                                                              DemocracyNow
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                                                                homemade sleeve puller. Locking rings are threaded onto this sleeve and gear cluster/bull gear bearings race in these two sleeves. Sleeves are held in case by large airings. A rubber hammer may have been able to do the job but the sleeve puller was more precise. I reused my airings on the entire rebuild without any leaks. Prongs are designed to be reused.

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                                                              • #49770
                                                                DemocracyNow
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                                                                  homemade sleeve puller. Locking rings are threaded onto this sleeve and gear cluster/bull gear bearings race in these two sleeves. Sleeves are held in case by large airings. A rubber hammer may have been able to do the job but the sleeve puller was more precise. I reused my airings on the entire rebuild without any leaks. Prongs are designed to be reused.

                                                                  Prongs and airings are O-RINGS

                                                                • #49771
                                                                  DavidPrivett
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                                                                    did you drive the tractor in 4 wheel drive on hard pavement much? even with a loose fit , it looks to me that there had to be a lot of load to get the wear that is there. I am just curious. with another thought are the tires the correct size to prevent them spinning at a to different rate?

                                                                  • #49772
                                                                    DemocracyNow
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                                                                      Never on solid pavement other than the several times of year I plowed the paved culdesac.
                                                                      This tractor was bought in 2002 .I believe the brass Bellville washers separating the worn axle drive gears from the differential housing were never installed at the factory. The other 2 brass Bellville washers in the differential were fine and reusable ,(shown in pictures). As was the brass pinion washer.

                                                                    • #49773
                                                                      DemocracyNow
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                                                                        Ps,Because those brass washers were not installed at the factory it took 1200 hours for those case hardened steel gears to wear their seats into the relatively soft cast iron differential housing. That original looseness plus the subsequent increase in gear lash / mesh of the other gears involved and they began failing.

                                                                      • #49774
                                                                        DavidPrivett
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                                                                          Do you feel you were able to get it good enough gear engagement or are you going to try to find a center gear case?

                                                                        • #49775
                                                                          DemocracyNow
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                                                                            I ended up buying a new center gear case. I must have not stated that him my rebuild….. sorry. Cannot remember the price from Affordable.
                                                                            Have used the 4wheel drive many times since the rebuild but use it only when necessary. Before rebuild it was engaged 24/7.
                                                                            But any 4wheel drive system should be bulletproof if manufactured correctly. I feel those perceived missing brass Bellville washers weakened the system.

                                                                          • #49777
                                                                            DavidPrivett
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                                                                              yes things in china are hit and miss as far as are all the parts in there, I bought a mower for my skid steer , it is a great bear brand , it was sold as having a problem so I got it cheap. so I powered it up and there was quite a grinding noise , it is full of oil . I removed the gear case and opened it up the drive gears bearly touched , so I bought a new gear case , which is a good one, still came out good price wise. but the original gear case should have never been let out of the factory and they would not eat the defect , I had to pay for it although they did give me free 3 day shipping from china.

                                                                            • #49779
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                                                                                More photos

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                                                                              • #49781
                                                                                DemocracyNow
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                                                                                  Item # 14 in some exploded views

                                                                                   

                                                                                • #49942
                                                                                  DemocracyNow
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                                                                                    Update 7/26/22 ,So far my rebuilt front differential is working perfectly. Have added 200 hours to that rebuild by moving dirt 800 feet to fill 1000 tires in a tire retaining wall. Will try to upload a picture. CTOA would have a better website if the administrators of the site would increase the file uploads.

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                                                                                  • #49946
                                                                                    DemocracyNow
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                                                                                      There are four of these gears in center gear case. Two had brass washers. The other two gears did not have these brass washers and failed due to excess lash from the gears wearing away their seats.

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                                                                                    • #49948
                                                                                      DavidPrivett
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                                                                                        I see the retaining wall, that must be quite a bit of hand work filling and packing the sidewalls , I do not know why but I was wondering is there anywhere in the US (california) where they (the govt) are going after people for using what they call has. mat. in buried appilications? I see people using them for house construction , that must be a real pain to get the thermo mass they are looking for.

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