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2R5 Differential Problem

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  • Rear Axle: 2R5 Differential Problem

    I had been hearing unpleasant clangs and bangs from the back of my 1949 2R5 truck for some time. I did not hear them continuously, so I was not able to fully locate the source. This truck needs pans under the full length of its drive train to keep oil off the floor of my garage. The last time I took the truck out I found the pan under the differential noticeably fuller than normal, so I ended my plan for a drive and put the truck back inside.

    I took the differential cover off and found the remains of one of the bolts that hold the large gear in place laying in the bottom of the case. Rotating that gear showed that 2 bolts are missing. The second bolt is not in the case. Because it will easily fit the drain plug I make the guess that it came out during some earlier oil change without me noticing. All of the remaining bolts are loose and held in place only by the locking clips. The two clips that lost a bolt are mangled. The loss of oil came from a hole having been punched into the cover. Thanks to our vendor list, new parts are ordered. The gears look good, and I can get the cover welded up.

    The repair manual shows 40 ft-lb for these bolts. This is not a lot, but the bolts are finger loose now. I make the guess that something was done to this differential, and tightening these bolts was forgotten. Does anyone have an opinion on this?

    The photos show the mangled clips, the remains of the bolt and a little bit of orange to highlight the hole in the cover. The hole is barely visible here, but the oil knows where it is.

  • #2
    It doesn't much matter when or why , that diff needs to be rebuilt . Everything needs to be taken out of the case and cleaned and cleaned again . I have redone several diffs that were not properly cleaned by someone or put together without regard to clearances , torque or preloads and started making noise again in short order . When you think it is clean , clean it again . Metallic particles hide in every little nook and cranny of the castings . Punch the tubes with a swab and solvent until the swab comes of clean . Pattern the gears and set the preload . You may need to disassemble several times to get it right , but if you don't it will sing from the start and wreck your new gear in short order . This is not a job to rush or guess .


    • #3
      I agree that it needs to be totally taken apart and rebuilt. It isn't a job for the timid (like me). I have the knowledge but lack the patience to do it slowly. Good luck, Bill.


      • #4
        I agree with what's already been posted. Especially if you have an overdrive. Not knowing the full history of the unit, where it came from, who has worked on it...there could have been not enough torque applied, too much, or inconsistent between the fasteners which would affect the overall torque performance. Add to that, the whiplash when the overdrive engages, and any weakness like a stressed bolt, and that's when one can either snap or begin to work its way out. Unless you know for sure, there could be the remains of one of the bolts still threaded in the hole.

        I am, at best, a backyard tinkerer. I have worked on some of my differential units, but none of mine are twin traction. The only way I would dive into one of those would be if I had a spare in case I ruined it by overestimating my capabilities. Otherwise, I think I would "bite the bullet," and pay someone who really had the correct tools, experience, and skill.
        John Clary
        Greer, SC

        SDC member since 1975


        • #5
          if you need them, I have 2 good axles with good bearings for your truck.


          • #6
            I'd replace the missing bolts, and any others that are questionable. After torquing and locking the bolts down, I'd rotate is slowly and check for backlash and bearing wear using, "feel" all the way around the ring gear. If it seemed OK, I'd button it up and run it. If it decides to fail again, you'll get plenty of warning, and you can then pre-plan for a total rebuild or replacement.


            • #7
              Thank you all for your advice. I know how I am. The advice given in post #6 is what I will do. This truck sat on blocks from 1988 to 2013, and I am not anxious to put it back there just yet. It may go back on blocks again after the new year and endure some disassembly, so just putting it back together for now will help me decide what I will do when it next comes apart.

              I was given a lot of advice in these postings: https://forum.studebakerdriversclub....r5-drive-notes
              I did everything that is suggested in those postings that does not require engine disassembly. That disassembly is part of my plan for after the new year. Any bullet biting and money spending that I can do will first go toward gaining the ability to exceed 35 mph and to pull an incline. If that is successful, then I will have to spend for replacements for my date code 1977 tires.

              I have an overdrive transmission on my bench, but not in the truck. I was given a lot of advice for that in these postings: https://forum.studebakerdriversclub....r5-drive-notes
              The kachinging that I have looked at so far would be for: 12v solenoid, shaft machining, driveshaft shortening. That installation will not happen unless I find a complete vehicle to take everything from.

              I am very lucky and very happy with this truck. I bought it when I could afford to buy one (1980.) I was able to keep it and keep it nice for the 25 years it sat on blocks, and it is driveable.


              • #8
                I have further information. I do agree with the advice given in posts 2, 3 and 4. This unit does need to be taken apart and properly refurbished. For me, this is not going to happen in the near future. I do have a plan, but many other things have to also work out for me before I do any disassembly that makes it long term immobile.

                I did some cleaning. I first put in a quart of 1/3 kerosene with 2/3 10W-40 motor oil. I have the differential on jack stands. I let the truck run just above idle with the transmission in first gear for maybe 5 minutes then drained that mix. I then put in a quart of straight 10W-40 motor oil then repeated the running as described above. The original draining and these two new drainings each had very noticeable amounts of fine metal shavings.

                As suggested in post #4 above, I looked at the back side of the bolting. The back side of all 10 bolts are in place, so the missing two are broken off. I now think those bolts were broken when I bought the truck in 1980. The man I bought it from told me that he broke and replaced one of the axles. I still have his business card. I wanted some history of the truck a couple of year ago, so I looked on the internet for that business. The business still exists, and a man with the same first name has very positive reviews of his work. I called, and it was the same man. He did not know any history. He had it only six months. He tried hot dogging it but received only a broken axle for his effort, so he decided that truck was not for him and sold it to me. I think what was unknown until now is that those two bolts sheared off when the axle broke which would have at least one of them rattling around for 40 years. Or, more likely, one broke then, and the second one broke just recently. That would explain the sudden banging and clanging that cause me to investigate.

                For now I will replace the broken bolts, check the others, and get on with my driving.


                • #9
                  I still agree with the advice given in posts 2, 3 and 4 about the need for a rebuild. I have read the repair manual a few times and am considering taking this differential out during the winter. I am intimidated by the instructions in the manual and by the long list of needed j-tools. I was a machinist at one time, and would not hesitate in taking this on (probably would have already) if I had use of a shop, but I do not. I do not yet have enough understanding of the assembly instructions to know if I need to make a full dis-assembly. I am interested in the preloads and the runouts for a start.

                  Does anyone have experience making this repair without use of a shop? Thanks.


                  • #10
                    Disassembly and a rebuild may be the best solution, but if the task is too much to take on right now, I would go with Joe Halls advice. With it cleaned up, and everything all tightened up, and it turns smooth, I believe that it will be fine for a while. As Joe stated "it will give you plenty of warning" if it's not right. If you want to go one step farther you could get some gear marking compound at the parts store. It is applied to the ring gear, then run the pinion past the mark and it will show the pattern that the gears are meshing at. Plenty of how-to's online for this procedure.


                    • #11
                      Thank you for your further advice. I already follow the advice given in post #6. With the broken bolts replaced the clanging caused by loose pieces of bolts is gone. What I do have is a single clang when changing direction. It is just one clang. I ease the clutch out just enough to move a little then let it coast through the clang before I accelerate. I have no clangs when driving.