Rebuilding a 63-79 Differential? - NCRS Discussion Boards

Rebuilding a 63-79 Differential?

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  • Gary R.
    Extremely Frequent Poster
    • April 1, 1989
    • 1798

    Rebuilding a 63-79 Differential?

    Just figure I would pass along some info, maybe most know maybe not?

    If you plan on rebuilding or sending out your diff, take the time to check the yokes(axles) especially if you have a 63-73 that is original. I check everyone I get in but you may find some places figure them in as part of the job. With a 74-79 it is very possible they're worn, they weren't anywhere as good as the 63-73-74's were. Most of the 74-79's had soft faces that wore away and caused some issues. If let go too long they will wear down and grind into the carrier and if it hits the seal then you could lose the carrier all together.

    I just finished up a '66 BB diff for a fellow NCRS member and although someone was in this diff before the axles were original. Not only original but the best I've ever seen, better then the current New or rebuilt in fact.

    As with most diff's this one had axle endplay, about 050-060". A lot of guys assume the axles are the cause and many times they are, but you really do have to check them and see. When I removed the axles and checked them they were in fact longer then any I've had in, new,rebuilt or original. I don't know the exact spec, if there is one, for the distance from the face to the snap ring- I always look for .180-.187. I had a discussion with someone recently who told me it was supposed to be .170-.175 which is shorter then I like to use. Joe L, John H if you know of this spec please let me know.

    With this set of yokes they were dead on .200" and not the cause of the endplay. The stock posi was the cause and typically sloppy, as are the new in the box ones today. I did some machining and fitting and now these yokes are good to reuse & for a long time I might add. I set the endplay to 005-008".

    So check yours before you ship it, it could save you $200+ alone. If the endplay is excessive check it when you get it back, if done correct it will be in the 005-008 range- regardless of original,rebuilt,or "new".

    Here are some pictures as well.

    Polished & tuned with original axles in place, the endplay was too tight at this point.



    Original yoke I reconditioned and ready to set.



    Here you can see after a 0015 kiss cut the face is pretty flat, rebuilt yokes aren't this flat!


    Done and ready to install.This one was 005"



    One last tip for you guys who have a 63-67 with the narrow housings. I mentioned this for years but the shims in the kits sold do not come with the correct case shims. They come with the stackable shims used in the wider housings, 68-79. I've found all kinds of shims in these older diffs from previous rebuilders, this is the correct type. I grind them to size for setup and preload. Be sure you know what type you have before you tear it apart.




    Good luck!
  • Michael H.
    Expired
    • January 29, 2008
    • 7477

    #2
    Re: Rebuilding a 63-79 Differential?

    Originally posted by Gary Ramadei (14833)
    As with most diff's this one had axle endplay, about 050-060". A lot of guys assume the axles are the cause and many times they are, but you really do have to check them and see. When I removed the axles and checked them they were in fact longer then any I've had in, Good luck!
    I found that as the positraction plates wear, the clearance between the shaft and diff cross pin increases. Years ago, GM sold selective shims that were to be installed behind the side gear clutch plates. The end clearance can be adjusted using these shims.

    The problem, though, is if you set the pinion gear lash to specs (.003", or something like that) the posi will forever chatter, even if using the correct posi fluid.

    Comment

    • Keith L.
      Expired
      • April 7, 2008
      • 378

      #3
      Re: Rebuilding a 63-79 Differential?

      I may be asking something most know but do you pull out on the yoke till the snap ring bottoms and measure the space between the yoke end and the posi shaft? Is this where you want the .005? And when the yoke is pushed in does it ride against the posi shaft? Or should it hit somewhere else first?

      Comment

      • Tom L.
        Extremely Frequent Poster
        • October 17, 2006
        • 1439

        #4
        Re: Rebuilding a 63-79 Differential?

        Sisnce the subject cam e up I'll ask. I have the rear end out of the car to restore the rear suspension and I was not planning on getting into a diff rebuild. There are no leaks, noises (excpt for a little chatter making slow turns when it is hot) and endplay is not excessive, about .025 and .028 (if my memory is correct). I took the cover off and drained the fluid yesterday. It was suprisingly clean, not black at all and no sludge in the bottom of the case. My plan was to change the posi clutches, seals and clean it up. Any input on this?? It's a '72 if it matters. Thanks!!

        Comment

        • Gary R.
          Extremely Frequent Poster
          • April 1, 1989
          • 1798

          #5
          Re: Rebuilding a 63-79 Differential?

          Mike
          I have all the selective shims here, they come in 005 increments and are commonly available from any rebuilder. The problem with them, like the T/A shims, is they are too wide for the type of posi I build. Ok for some using the stock posi setup with the springs, I never do. I have measured many used clutches and surprisingly there isn't a lot of wear on them. I always use solid steels, never fiber coated or the old snowflake(slotted) clutches.
          I have never had one of my posi chatter.
          Interestingly I just had occasion to check a new loaded posi, with the springs out the endplay in the side gears was 030" on both sides. Bad is not the correct word for that setup.

          Keith
          You can use a dial indicator or feeler gauge to measure the side play. Again in typical stock type build you have to be careful you're not moving the side gear as well. In that new posi mentioned above it was very obvious.

          Lynn
          72 are good units, ( I own a 72), a lot depends on the usage and power of the car. If you're not going to hammer the car, your stock setup is ok. I don't like the clutches used in it but that's your call. I never use a posi in stock configuration, I polish and tune them all as shown in the picture. Your endplay isn't bad for a stock unit and may all be in the posi set up or wear in the cross shaft hole. I'd suspect it's the posi setup. Since you have it out, remove the side yokes and measure them to see.

          Comment

          • Tom L.
            Extremely Frequent Poster
            • October 17, 2006
            • 1439

            #6
            Re: Rebuilding a 63-79 Differential?

            Hi Gary, i took the time to re-measure the endplay using feeler gauges between the yokes and cross pin. My initial numbers were off a bit, the original methid of measurement was questuionable.

            Endplay is .018 on the pass. side and .023 on the drivers side.

            From the outer edge of the snap ring groove to the end of the yoke was .179 on the pass. side and .181 on the drivers.

            All this was better than I expected. As far as the usage goes, it's a stock LS-5 and is used primarily for cruising. The biggest reason I was going to address the clutches is the chatter drives my wife crazy, while we share its usage and in theory it's her car except on work days. Based on all this, do you think it's worth fooling with the clutches?

            Comment

            • Gary R.
              Extremely Frequent Poster
              • April 1, 1989
              • 1798

              #7
              Re: Rebuilding a 63-79 Differential?

              Lynn,
              The spec's on your diff are pretty good, not as tight as a blueprinted diff but better then a lot of rebuilts I've seen and had to correct. All in all if you were to use it as it is you're probably ok.
              I don't like the clutches used in your year or the rough casting on the posi. If 2 bottle of additive didn't remove the clutch chatter then the other way is to Tune it and that will stop it. Is it worth the time and money to do that, you have to decide. If it were mine I would but again that's your call.
              If you remove the posi,keep in mind the shims used in your setup are ground cast shims that will snap many times hammering them back in. I've found some so lose there is no preload and others so tight I had to use a bar to remove them. I don't like case spreaders but those are the best way to install the cast shims if reusing them.
              I would read over all my threads on DC on diff rebuilding before you make up your mind or you can call me with questions.
              Gary

              Comment

              • Tom L.
                Extremely Frequent Poster
                • October 17, 2006
                • 1439

                #8
                Re: Rebuilding a 63-79 Differential?

                Thanks Gary, since there are no obvious problems I think I'll be just be cleaning it up and re-sealing it. Not sure if I want to get into it that deep with it working OK now. We'll see what the furure brings. Have fun!!

                Comment

                • Tom L.
                  Extremely Frequent Poster
                  • October 17, 2006
                  • 1439

                  #9
                  Re: Rebuilding a 63-79 Differential?

                  One thing I forgot to ask, I remember that in one of your articles you suggested a specific brand of seal for these things. I looked and can't find the part numbers. Could you let me know what the pinion and side yoke seal part numbers are? Thanks!!

                  Comment

                  • Gary R.
                    Extremely Frequent Poster
                    • April 1, 1989
                    • 1798

                    #10
                    Re: Rebuilding a 63-79 Differential?

                    PM me and I'll get them to you.

                    Comment

                    • Paul L.
                      Expired
                      • November 1, 2002
                      • 1414

                      #11
                      Re: Rebuilding a 63-79 Differential?

                      With a 74-79 it is very possible they're worn, they weren't anywhere as good as the 63-73-74's were.

                      Gary,
                      That sentence confuses me. Were the 1974s on the not-as-good list?

                      Comment

                      • Gary R.
                        Extremely Frequent Poster
                        • April 1, 1989
                        • 1798

                        #12
                        Re: Rebuilding a 63-79 Differential?

                        Originally posted by Paul Latour (38817)
                        With a 74-79 it is very possible they're worn, they weren't anywhere as good as the 63-73-74's were.

                        Gary,
                        That sentence confuses me. Were the 1974s on the not-as-good list?
                        Sorry Paul
                        Most of the 74's I see are not too good, it seems to be the parting year on yokes.I had a few good ones not many. Of course I've had earlier yokes that were bad too but most of the 74 run and 75-79 were not too good.

                        Comment

                        • Wayne M.
                          Expired
                          • March 1, 1980
                          • 6414

                          #13
                          Re: Rebuilding a 63-79 Differential?

                          Originally posted by Gary Ramadei (14833)
                          Just figure I would pass along some info, maybe most know maybe not? ........
                          ------
                          ------
                          One last tip for you guys who have a 63-67 with the narrow housings. I mentioned this for years but the shims in the kits sold do not come with the correct case shims. They come with the stackable shims used in the wider housings, 68-79. I've found all kinds of shims in these older diffs from previous rebuilders, this is the correct type. I grind them to size for setup and preload. Be sure you know what type you have before you tear it apart.




                          Good luck!

                          Hey Gary -- I have only two diffs currently open. My original '65 carrier cast # 3876476 N (I assume is the narrow one you refer to) has only 2 side bearing shims; a 0.072" (in notch in, 1 notch outer perimeter) on one side, and a 0.086" (2 notches in, 4 notches out) on the other bearing side. So this makes the carrier a narrow design, right ?

                          My second diff. currently on the bench is carrier # 3899143, with stamped assembly number 2AL 10 22 68 W; so originally an early '69 3.08 posi. But the posi case is 2nd design 4-series Eaton EDB 32298 with GM 4.11 gearset with 1973 dates, so obviously replaced/converted 5 or more years after carrier was assembled.

                          Now I haven't pulled the posi case out of this carrier, but I see that one side has only a thick spacer (could it be the cast iron 0.160" x 3.0" dia that the parts catalogs refer to for '67-up ? although it looks more like at least 0.20" thick). The other side bearing has a stack of 4 shims, probably in the 0.064 to 0.086 range. Is this the way the wider carriers are set up from the factory ?

                          Comment

                          • Gary R.
                            Extremely Frequent Poster
                            • April 1, 1989
                            • 1798

                            #14
                            Re: Rebuilding a 63-79 Differential?

                            Wayne
                            I honestly don't know why the thin shims, 055- .095", have the notches in them? Maybe John or Joe knows? Maybe different applications 45 years ago?
                            If you look at the carrier with the cover off you'll see there is a cast step for the wider ones and straight for the narrow. The narrows used a cast ground shim, I've never seen an original factory setup with multiple stacked shims. Some rebuilders do that. I still have old vette magazines showing them hammering in the stock cast shims. A lot of times that is enough to break them.
                            The preload on the cases vary a lot with these too. Some I can remove by hand, others require a bar or the old wrench walk out trick. To attempt to reuse those shims with new bearings or gears is a mistake. The lash is going to be off for sure- unless the rebuilder is ball parking dimensions, like +/- 005" which is pretty bad.

                            Ok so here is a test for you.
                            What is this one I have here?

                            Comment

                            • Michael H.
                              Expired
                              • January 29, 2008
                              • 7477

                              #15
                              Re: Rebuilding a 63-79 Differential?

                              Side carrier bearing shim thickness chart for 1966. I think the same notch code continued for several model years.
                              Last edited by Michael H.; June 21, 2011, 08:43 PM.

                              Comment

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