Differential and transmission reliability question

Discussion in 'SRT Hellcat General Discussions' started by GrndFnk, Jan 23, 2016.

  1. GrndFnk

    GrndFnk VIP Hellcat Member

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    I am aware of the driveshaft issues. Seems the axles take allot of abuse with only a few failures that I know of.
    So how are the diffs and transmissions holding up, and has anyone determined a limit as to what they will stand ? Are there any upgrades to the HP90 offered yet ?
    Thanks.
     
  2. Top Cat

    Top Cat Gold Member Hellcat Car Club Gold Supporting Member Fastest Cat/Record Holder HCC Charter Member

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    I broke the diff case, only one that I know of so far.
    TC
     
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  3. GrndFnk

    GrndFnk VIP Hellcat Member

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    Interesting. I guess your car and the wifes would be the most apt to find the weak links...
    Mine has 300 miles on it without issues except right off the bat when it had 12 miles on it, my first time around the block it would not engage 2nd gear under really light throttle, sort of free-revved but I knew enough to get off the throttle and give it a few seconds at which time it would eventually engage. This went on for a while then I took it out on the road and laid into just a little and let off when I thought it was about to shift as not to scorch the clutches and it started working correctly. I am guessing there was a chip caught up in the valve body and it worked its way out, who knows.
    It is impressive that the trans seems to take what some of you folks can give it so far.
     
  4. graycat

    graycat Automobile Aficionado Extraordinaire Staff Member

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    I believe that Top Cat is the only person to break a diff in one of these cars and I've have saw (I've looked, a lot) zero transmissions fail.

    There are only two "weak links" that I've heard of or saw. One (I experienced myself) crank shaft pulley slip and number two, rocker arm failure,
    they are cast and sometimes break. So other than the driveshaft problems which you've mentioned it seems that the driveline is pretty tough and
    except for the really "hot" cars like TC or his lovely bride, most of us will likely never have issues with those parts. There only seem to be two likely
    engine issues unless you start pushing a lot more air and fuel into the motor. The two engine issues seem to happen regardless of how you drive
    the car and regardless of any "mods" made to the car.
     
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  5. GrndFnk

    GrndFnk VIP Hellcat Member

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    I suspect the crank pulley failures on STOCK engines might, and I emphasize might have something to do with tolerances being a little off and/or the manufacturing process IE: pulley ID high limit vs crank OD low limit and new CNC operators at the plant working with a new engine. Again, who knows.
    There is a reason Chrysler and GM do not pin, or key the pulleys from the factory and it isn't to save a buck...it has to do with vibration and harmonics and weakening the snout of the crank, etc and I was advised that if I keep the engine stock and within its operating parameters that I will never need to worry about it. We'll see. The GM 6.2L and Z-06 engines are a press fit from what I understand without any reported pulley issues that I am aware of.
    It will be interesting to watch the '16's such as mine and see what goes with the pulleys.
     
  6. graycat

    graycat Automobile Aficionado Extraordinaire Staff Member

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    I have personally saw two Z06 engines spin the crank pulley. They both belong to guys that live in the Knoxville TN area. I'd also like to add that my
    Hellcat that is still waiting on a replacement engine and will only be mine until the 2016 arrives to replace it, has zero mods done to it. This car is one
    of 12 Hellcats that I'm aware of with the crank pulley issue. The 11 besides mine are known to me from members of this site only so I have no way of
    knowing how many others it may have happened too.

    I have to say that harmonics of a pinned crank, especially one that is pinned twice, 180 degrees apart, can be dealt with during the balancing of the
    crank, rods, pistons and harmonic balancer assemblies. Plus, a pinned crank with round pins instead of the keyed or "square" cut crank and balancer
    would not be prone to stress fatigue or cracks due to the removal of metal but would be much less likely to allow the balancer to slip.

    I'm in no way trying to start an argument or say that you or anyone else is wrong, but I am saying that I can't "square" the opinion with my own personal experience or knowledge.
     
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  7. GrndFnk

    GrndFnk VIP Hellcat Member

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    Interesting that the Z-06's have had the same issue.
     
  8. Top Cat

    Top Cat Gold Member Hellcat Car Club Gold Supporting Member Fastest Cat/Record Holder HCC Charter Member

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    One of the benefits in switching to the ATI OD pulley and pinning it.
    TC
    BTW, money always has a play with decisions;)
     
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