ring and pinion swap

Engine, Trans & Driveline

  1. Green72

    Green72 Well-Known Member

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    Going to swap the gear out of my 8 3/4. it will be my first time. The rear end has very few miles on it and works perfectly.
    Could someone humor me with a parts list that I will need.
    Thanks
     
  2. #41

    #41 Well-Known Member

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    Just a gasket and some silicon for the gear set. You can reuse the gear oil if clean enough. If you put new in and use a suregrip, be sure the gear oil is ok for suregrip, or buy the additive. Some people don't use a gasket but I have not had much luck with that. If everything is low mile, you should be able to reuse the foam gaskets at the axles. When you slide the axles out, be careful not to tear them and don't rest the axle on or rub the axle spines on the inner axle seals.
     
  3. rmchrgr

    rmchrgr Well-Known Member

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    Are you changing the whole drop-out center section or installing a different ratio gear set into an existing assembly? If it's a gear set it's more about tools than parts. If you are in fact changing the ring and pinion you will a bunch of specialized tools to set the thing up. First and foremost you need a pinion depth tool, you really can't just drop a new gear set in to a case and expect it to be perfect. If you're going to re-use everything else, make sure you have a way to get the bearings off cleanly otherwise you're going to need a new pinion bearing set at minimum. You will need a variety of shims to get the proper pinion depth. What rear is it? If it's a 489 you will need a new crush sleeve. Ring gear bolts are left hand thread so don't try to power them off with an impact without reversing it. Loctite them down when re-installing. Get some checking compound to check the gear pattern, a spanner to set adjuster end play, dial indicator with stand to check backlash, 250 ft-lb torque wrench with cheater bar, pinion yoke holder, bearing race drivers, pinion depth checking bearing, inch lb torque wrench to measure breakaway torque... it's also nice to have a way to hold the housing when working on it. Don't forget fresh gear lube, new pinion nut, Sure Grip limited slip additive and a new housing gasket. I'd order a new pinion seal and axle seals "just in case". Have fun!

    https://www.hotrod.com/articles/mopp-0308-mopar-rear-end-gears-set-up/
     
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    • 451Mopar

      451Mopar Well-Known Member

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      I found it easier to set pinion depth by just using a straight edge, a machinist 1-2-3 block, and a few feeler gauges.
      Because the definition of pinion depth is the distance of the head of the pinion to the carrier centerline, you can use the bottom of the carrier bearing bore as a reference point to the centerline.
      8-3/4" uses a 3.2650" bearing bore, so half of that (centerline) is 1.6325" from the bottom of the bearing bore to centerline.
      Last 8-3/4" I did had a pinion that needed to be installed 2.7210" from centerline, so subtracting the 1/2 bearing bore diameter of 1.6325 from the 2.7210 pinion depth results that the pinion head needs to be 1.08850" below the lowest part of the carrier bearing bore.
      With the 1-2-3 block used to take up 1.000" and being square to the pinion head so part of the block is directly under the lowest part of the bearing bore, there should be a difference of just 0.08850" from the 1-2-3 block to a straight edge placed across the bearing bores at the lowest (or closest) point if the pinion depth is correct. I'm just saying I found this method easier and more consistent than using a "universal" pinion depth tool, or the Raytech pinion depth tool.
      The factory tool that centers in the bearing bores is maybe easier?, but I don't have that tool.

      Also, the ring gear bolts are left hand thread on the 8-3/4".
       
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      • rmchrgr

        rmchrgr Well-Known Member

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        Guess there is more than one way to skin a cat. Not everyone has a good machinist straight edge or blocks though, I don’t.

        I have the complete tool from T&D. It sits where the carrier bearings ride. Was expensive back when I bought it ($300) but I’ve had it for over 20 years. It’s way more now unfortunately. Those $120 universal anodized pinion depth checkers are garbage.

        But beyond the pinion depth tool you’re going to need all the other tools as well, just no way around it.

        Here is an article on the Ratech tool which is super cheap.
        https://www.hotrod.com/articles/t-and-d-machine-pinion-depth-tool/
         
        Last edited: Jan 29, 2021
      • 451Mopar

        451Mopar Well-Known Member

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        I'd like one of those T&D tools some day, but they are about $500 now.
        https://www.amazon.com/Machine-Products-11001-Deluxe-Checker/dp/B003OU2DXU

        The Raytech tool is decent for the price. It is just a bent piece of metal of known height that sits on the pinion head and gives a known height to measure to the carrier bearing bore. Same principle I used with the straight edge.

        The clamshell type bearing puller is nice to have if you need to change shims after the bearings are pressed on.
        https://www.doctordiff.com/differential-carrier-bearing-puller.html

        You don't exactly need the spanner wrench, but it makes the carrier side adjustments easier
        https://www.doctordiff.com/8-3-4-spanner-wrench.html
         
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        • Danny Boy

          Danny Boy Secret of life is enjoying the passage of time JT

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          As an aside and generally speaking, how knowledgeable are shops now in changing out gearsets?

          I wonder if this is taught in tech schools?

          The reason I'm asking is because I don't have the equipment and knowledge and was considering to pay to have it done.
           
        • Billccm

          Billccm FBBO Gold Member FBBO Gold Member

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          I recently took my axles and diff to Tucson Differential. I ordered the ring and pinion from Dr Diff and they provided the bearings and labor. It was still $700 with me R & R labor.
          They recommend skipping the gasket and using Toyota FIPG. So far no leaks.
           
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          • rmchrgr

            rmchrgr Well-Known Member

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            Yeah, realistically by the time you round up and pay for all the tools and parts, it’s probably easier to just take it somewhere and have it done.

            In my area there are a few shops that specialize in “driveline” work, its fairly common I would think. They are generally not “race” oriented but can usually handle whatever you bring them. Besides muscle car/drag racers there are certainly plenty of 4x4 guys out there that deal with diffs all the time, plus service trucks etc.

            Unless you plan on doing a lot of diff work, it’s really not worth the expense of buying all the tools. They don’t get used much, are expensive and can take up a lot of room.

            I have not done too many myself but I made it a point to learn how to do it and getting the tools was a necessary part of that.
             
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            • tallhair

              tallhair Rufus "Mod-hair" Firefly Staff Member

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              Is that used in place of your $300 dollar tool and is it accurate? Guys in article seem to like it.
               
            • tallhair

              tallhair Rufus "Mod-hair" Firefly Staff Member

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              Saw this handy bracket made of 3 pieces of angle iron. Mounts to engine stand to secure the housing.

              On Scott’s Speed Shop channel

              Second pic a little dark but that it bolted up


              A41DE878-E840-41F6-9378-70E62325DB98.png B0AE7681-94A8-4A3A-8A6A-F97DB3FCC15D.png
               
            • dvw

              dvw Well-Known Member

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              I would say the biggest hurdle is reading the pattern. You can set pinion depth with a tool and it's still not correct. I do them and still find it not very profitable. You need at bare minimum. Dial indicator. Correct press, tubes, pullers to remove and install bearings. Ft/lb and in/lb Torque wrenchs. Spanner wrench. Strong fixture to hold the housing during assembly. Then several attempts to get the pattern dead on. And the knowledge to realise what pattern is actually correct. Truthfully $200 labor is a bargain.
              Doug
               
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              • rmchrgr

                rmchrgr Well-Known Member

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                The article and photo are a little misleading since the title says T&D. To me it looks like the Ratech tool is being used in conjunction with what looks like the T&D pucks. Probably not the best article to post, my apologies.

                If that's how they are using it, it's accurate because of the pucks which locate the indicator squarely, not the Ratech tool itself. You need a way to keep the measuring block square and steady. If you go through the trouble of setting up the pucks in the adjuster caps, the cheap tool seems redundant though if it's a per-determined height it could save some set up time.

                And yes, Doug is correct in that just because the depth is correct does not mean the gears are meshing properly. Sometimes you get lucky and it's close but often you go through several rounds of trial and error until the pattern is right. That's why you absolutely need the checking bearing so you don't have to press your brand new bearing on and off the pinion every time you have to add or remove shims, it's a huge time saver. You'd be pulling your hair out if you had to do it that way.

                You can see why it's an expensive proposition - not only do you need the tools but it can take a long time to do it correctly especially with older housings which may not always be perfect to begin with. Time is money when you run a shop.
                 
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                • Green72

                  Green72 Well-Known Member

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                  Ok so I am going to do this myself, because I want to! I have most of the tools anyway.
                  As far as the pinion depth tool, can I accomplish the job by using a checking bearing and trial and error until pattern is good?
                  It's a 742 case and I am changing pinion and ring gear not entire center section
                  Already lots of info in this thread that I didn't know
                  You guys are awesome
                   
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                  • khryslerkid

                    khryslerkid FBBO Gold Member FBBO Gold Member

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                    If you haven't purchased any parts yet contact Cass at Dr. Diff. https://www.doctordiff.com/
                    Not a better person to deal with and he has everything you need at a reasonable price.

                    I rebuilt my 742 last year and he was very helpful. I even sent him pics of my gear pattern and he instructed me in what I needed to do to fine tune it.

                    Also he sells Nitro gear sets which he doesn't advertise and they were great. Not noisy at all after the install. They are very reasonably priced compared to what's out there and have very good ratings. You have to ask about them. He'll talk to you on the phone or emails with expertise.

                    The most valuable tool I found doing the job was a inch pound "guage" torque wrench. It will let you know the preload on the pinion better than guessing at it. Good luck!
                     
                  • bee71

                    bee71 Well-Known Member

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                    Agree with Nitro gears. Yukon are nosier.
                     
                  • Runcharger

                    Runcharger Well-Known Member

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                    To me: It's kind of a shame to knock down a nice center section. There are lots of cases around, I would consider building an entirely new center section. You can sell what you have too to help offset your costs. Advertise it while it is still in the car. Cass is a great guy to go to for the new parts.
                     
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                    • tallhair

                      tallhair Rufus "Mod-hair" Firefly Staff Member

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                      Why are you changing the gears? I may have missed it but didn’t see the reason.

                      If you are going to a lower gear for acceleration and this is say a 2.76 or 3.23 you could keep it and swap out if you want to make a trip.
                       
                    • Green72

                      Green72 Well-Known Member

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                      I built an RB based 512 for this car and have based the engine and converter for 4.10's. The car has 3.23's currently. Please everybody don't start telling me that I won't like the 4.10's. I am fully aware of the drawbacks and advantages. I also have a Gear Vendor Overdrive waiting to go in. It makes more sense for me to order a new center section but I really want to gain the experience.
                      I am still wondering if I really need the pinion depth tool? Can the pinion depth be determined by using trial and error and a checking bearing to accomplish a good pattern?
                       
                    • Runcharger

                      Runcharger Well-Known Member

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                      Yes: If it's a 489 and still using a crush sleeve I stretch the original out by hammering it extended again for the initial setups. Then use the new one on the final assembly or convert it to the crush eliminator kit. Use the original shims as a baseline.
                       
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