Sure Grip unit feels much better than Eaton TruTrac did..

Transmission and Drivetrain Tech

  1. jbc426

    jbc426 Well-Known Member

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    I recently replaced the differential in my 8 3/4 with a blueprinted Sure Grip unit from Doctor Diff. I was getting a high speed 95+ vibration and the passenger side Green Stripe bearings were getting noisy after a few thousand miles. The driveline was smooth until I exceed 95 mph, and then a significant vibration would start and increase in intensity as speed went well into the triple digits. It didn't make for a reassuring feeling while it happened.

    According to Cass aka Doctor Diff, the TruTrac's have an design issue that doesn't stabilize the splined components that the axles fit into allowing them to move around inside the TruTrac carrier. He says it's the only differential that he has seen designed with no provision to set that clearance inside the unit. He spoke with them about it, and hears similar vibration and early wheel bearing wear stories all the time from all over the world. I was able to grab my rear wheel with the car jacked up at the 3 & 9 O'clock points and shift the wheel back-and-forth like it was turning left or right slightly.

    I've yet to get on a track to see if the high speed vibration is gone, but I did immediately notice how much more solidly the car hooks up on launch. I knew right away why they called the unit a Sure Grip. It feels exactly like that, where as the True Trac never gave the feeling of solidly hooking up. It worked, but it just felt different. Sure Grip feels exactly like it's name implies. Mopar is awesome!

    JohnRace2 (Large).jpg
     
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    • brian6pac

      brian6pac Well-Known Member

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      I put one in my pick up truck and it has been awesome, now my friend blew one in a bunch of pieces in a 9", 520 cu in ford with a lenco, they did give him a new unit but said this was the one and only time they would do it. He also broke a Richmond gear set, knocked 4 teeth off the ring gear.
       
    • brian6pac

      brian6pac Well-Known Member

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      Next time I jack up my truck I will check the play.
       
    • Dana

      Dana FABO Vendor FABO Vendor

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      I had a high speed vibration. I never narrowed it down to the pig. Then I smoked the tru trac in october. The 4th launch at Norwalk with a 318 probably making around 300 ft. Lbs. Street tires, coming out at 2500. They advertise 550 horse capability. But it came packaged in rice! Going back to my sure grip. So $1600 dollars divided by roughly 2000 miles, I'm sorry ma Mopar for going astray.
       
    • jos51700

      jos51700 Green Bearing thread connoisseur

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      I can't see see how that design would work for ten minutes with nothing locating the slip spline carriers.
       
    • DARTGAME

      DARTGAME SuPeRcHaRgEd

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      Glad I saw this thread. I was planing on getting a tru-trac to replace my perfectly fine sure-grip unit only because wanted to change gear ratio. I read your other thread about high speed vibration, hope this cures it for you.
       
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      • moper

        moper Well-Known Member

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        NO offense but I've installed more than a couple of them from Cass. One is road raced severely and has been under the car for 12 years now. He regularly exceeds 150 in a 4K lbs E body. NO vibrations from that diff. Maybe it's a tolerance stack deal and I've been lucky. But I've not had one complaint ever about them. Even in heavy cars with 505" engines going 170mph.
         
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        • moparmat2000

          moparmat2000 FABO Gold Member FABO Gold Member

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          Glad i got the rebuildable clutch type sure grip unit (similar to oem sure grip) from Cass when i ordered my gears instead of the Eaton truetrac. Wasnt in my budget, i was upset that i didnt have the extra scratch for it, now i'm glad i didnt.
           
          Last edited: Jan 29, 2018
        • MRGTX

          MRGTX Well-Known Member

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          Fantastic.
          I have a brand new one from Moser ready to go in my car.

          Are there other reports of this problem? While I don't doubt that jbc experienced this, I'm finding it incredibly hard to believe that there is such a serious design problem.
           
        • MRGTX

          MRGTX Well-Known Member

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          Sounds like Dr. Diff's PhD is not in the field of business ethics. He still sells the damn thing.

          Mopar 8 3/4" (8.75) Eaton Truetrac Differential
           
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          • KnuckleDuster

            KnuckleDuster Well-Known Member

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            Actually , he talked me out of buying one, citing excessive side play clearances. He told me he was trying to get Eaton to fix it, but was making shims to correct it. He did not have them ready at the time, and so he listed them as out of stock, even though he did have the units.I have never heard anyone who has actually dealt with him to say anything derogatory about his ethics, in fact, quite the opposite.
             
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            • snailpower

              snailpower Well-Known Member

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              Was the original vibration MPH dependent or rpm dependent? I have a tru trac and trying to find a vibration I'm getting at 75mph+.
               
            • MRGTX

              MRGTX Well-Known Member

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              I just called Moser to find out what they thought. They’ve gotten no complaints and we’re aware of no problems with the TruTrac.
               
            • jbc426

              jbc426 Well-Known Member

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              It was consistently mph dependent, and always began at 95 to 98 mph. It increased in intensity as mph increased.
               
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              • jbc426

                jbc426 Well-Known Member

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                Not every Truetrac has the issue. I'm not sure if it's because most people keep it under 95 mph or the combination of the Truetrac, high speeds and the changing to green stripe bearings has something to do with it.
                 
              • MRGTX

                MRGTX Well-Known Member

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                Huh... well, I guess I will find out for myself this spring. I have between now and when the salt is gone from the local roads to wonder if mine will have the same problem.

                Did anyone measure the endplay on the axles? Were they out of spec?
                 
              • savoy

                savoy Well-Known Member

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                Wonder how these stack up against a Detroit Locker for use on strip and street with 700hp+ in the car?
                 
              • Mrpatel

                Mrpatel 512Dart

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                I have one with no issues at 600 hp. Motor is out and stepping up to 700 for spring. Not sure what the concern is? I called them and they said to only use Lucas oil and not valvoline.... seams to work fine. Pick the phone up and call them and use your own judgement.
                 
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                • fratzog lover

                  fratzog lover Well-Known Member

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                  No problems at high speed. Nice black stripes at low speeds.
                   
                • jbc426

                  jbc426 Well-Known Member

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                  I find it peculiar that someone used the disagree button on something that is a simple fact, such as the one above. Not the first time, but I don't get it. I disagree with your disagreement. LOL.

                  Then again this country is full of folks that will disagree with all kinds of things that are true.
                   
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                  • moparmat2000

                    moparmat2000 FABO Gold Member FABO Gold Member

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                    Yaaaay !!!!! hurray beer.
                     
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                    • MRGTX

                      MRGTX Well-Known Member

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                      @72bluNblu what do you disagree with?

                      Dr Diff is invoking a PhD in his business name...which may be a "doctor" more along the lines of Dr Pepper or the Rug Doctor...but still, I doubt that he has a PhD in business ethics. Was I actually wrong about that?

                      He is evidentially strongly advising against a product...for which he's also willing to take your $500 in exchange for. :rolleyes:

                      It doesn't look good.

                      I don't know the man. I didn't even know it was one guy before this thread. My comments were mostly meant to be silly...but also made out of my own frustration since I just invested in one of these units on the basis of trusting the reputation of a product and trusting the word of a competing vendor who stands behind their work.

                      I do believe @jbc426 about his observations and it makes me wonder if I'll have to deal with this after pouring in a lot of time, money and work into the Dart this winter.
                       
                    • jbc426

                      jbc426 Well-Known Member

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                      I have yet to get the car up to the high speed required to verify the original vibration issue has been eliminated. That being said, the car just feels better while accelerating out of the hole with the Suregrip as opposed to the TrueTrac. It just feels more solidly driven by both rear wheels.

                      I still have my fingers crossed and I generally try to keep it under 100mph around here, but I will update once I gather the high speed data.
                       
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                      • 72bluNblu

                        72bluNblu FABO Gold Member FABO Gold Member

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                        You’re 100% off base about Cass, aka, DrDiff. That’s what I disagree with. I’ve done business with him for years, bought everything from axles to disk brakes, even a brand new 3rd member with an Eaton Trutrac for my Duster that’s going in with my t56. I’ve called him, emailed him, bought products, you name it. He’s helped me out a few times diagnosing differential issues, even though there wasn’t any parts I bought from him involved. Even shipped me a couple parts overnight to get me back up and running. His knowledge and customer service is the best I’ve encountered in the Mopar world. So yeah, I disagree with you suggesting his ethics are suspect, that’s total BS.

                        As for the truetrac, I haven’t heard of any issues with them before this post, and I talked to a bunch of people. I’m pretty sure @autoxcuda and @GMachineDartGT both run them in their cars that are seeing plenty of track time. I’m not discounting jcb426’s assessment, and I’m not saying his truetrac wasn’t the source of his problem. But lots of people run them successfully. I’m definitely concerned about some of the issues he had because I haven’t installed mine yet, but there are plenty of parts in motion. I’d be interested to know if anyone else with green bearings has the issue, because I know the folks I talked to all run tapered bearings. Or maybe jcb426 just got a bad unit with excessive clearance. Or maybe it’s some combination of parts. Sucks with an expensive part like that, but it does happen, nothing is 100%.
                         
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                        • KnuckleDuster

                          KnuckleDuster Well-Known Member

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                          I bought a Powr Lok unit from him. He could have easily bit his tongue and got a bigger sale, but wasn't willing to.
                          I guess it was a bad batch. He said he had a bunch but wouldn't sell them until either Eaton or he made it right. That's called integrity in my book. Maybe the ones Moser got weren't affected, I really doubt they would sell anything they weren't sure of either, from what I have heard from people dealing with them. I just know Cass was very honest and helpful with me, and I appreciated it. I wasn't trying to give anybody sleepless nights worrying about something they bought. Cass didn't mention a design flaw with the Trutrac to me, only that he didn't like how the ones he had on hand came out on clearances. He does have an asterisk on his description that they require a thrust block, maybe that is the design flaw referred to? I don't know...
                          All I can say, is that if he wanted, he could have made more cash off me on the chunk and related parts, but instead I got a little free education.

                          I put him on the list of best Mopar vendors I have dealt with.

                          Cass (Dr Diff)
                          Don Gould (FBO)
                          Dick (Firm Feel)
                          Dante (Dante's Mopar Parts)
                           
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