Question about Rear Gear DECEL whine

Discussion in '2005+ Mustang GT 4.6L Tech' started by 1950StangJump$, Dec 29, 2018.

  1. 1950StangJump$

    1950StangJump$ forum member

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    New Magnum Xl and 4.10 gears. I have a slight DECEL whine ... probably not enough to worry about. But, I’m curious ....

    If the whine starts at DECEL, but then goes away when you disengage the clutch and coast, would that imply I’m actually hearing something other than the rear end (like transmission or engine harmonics)?

    Or does rear end DECEL whine go away with clutch disengagement?
     
  2. mustanger

    mustanger Junior Member

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    I would think a slight rear end whine on decel could go away with clutch disengagement. When you are coasting the engine braking is causing the gears to be loaded against the coast side of the ring and pinion but by pushing the clutch in you would lose most of that force. If it was a transmission whine it seems like it would only be in a particular gear.
     
  3. 1950StangJump$

    1950StangJump$ forum member

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    Gotcha, thanks. After I made this thread, I also concluded it was the rear end.

    Now, I just have to decide if the relatively slight whine is worth me driving 2 hours to have the shop fix it.

    I do tend to think that, with steeper gears, a slight whine might occur because of manufacturing tolerance differences no matter how perfect the install. So, I might go through lots of trouble only to end up no better off.

    And that’s assuming the shop doesn’t tell me my expectations are unrealistic
     
  4. mustanger

    mustanger Junior Member

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    You may definitely want to take it back to the shop that did the install and see if they will fix it. The thing with whine is that it normally doesn't get any better and will probably get worse over time.
     
  5. 1950StangJump$

    1950StangJump$ forum member

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    Yea, leaning that way. It’s subjective though —- you might hear it and tell me I’m crazy :)
     
  6. 46addict

    46addict 13726548

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    I had the same issue and it turned out to be a pinion preload problem. In my case I had done a driveshaft swap which necessitated a new pinion yoke and it turned out I lost the preload setting from swapping yokes. If you're in the same boat from doing a Magnum XL swap you may have to get the rear end gears set up again. Not sure if I got shafted but that's what my rear end guy told me. I got the car back and I don't hear a peep. I had them reuse the same 3.73 gears I had in the car. About 100 miles were driven with the noise going on.
     
  7. 1950StangJump$

    1950StangJump$ forum member

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    Thanks. I go back on Tuesday. By then, I will have put about 400 miles on them though, so I assume they will have to do new gears. I also assume that they might push back a little, since the whine is not terrible.
     
  8. eighty6gt

    eighty6gt forum member

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    I would live with it

    all of my gears 3.73+ have made some noises

    They did not get worse over time.
     
  9. TexasBlownV8

    TexasBlownV8 Formerly TexasBlownV6

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    410's are tricky enough as it is to get ultra quiet, and a little whine only on decel in a certain speed range would make me think the backlash is slightly off. But if it is constant at all speeds, that could be a bigger issue, even a problem with the gears themselves. One thing I'd check is to make sure there is no metal flakes in the fluid, which can happen with a slight defect, even if the gears are set up properly, and result in such a whine.
     
  10. Norm Peterson

    Norm Peterson corner barstool sitter

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    Got a few questions (I'm looking at either 3.73's or 4.10's for road course duty, hopefully with a Magnum XL).

    Did any of those gearsets originally come with the car(s)?

    For any that weren't factory-original, who did the install (dealer, independent shop or specialist, self or friends)? Were they Ford gears or Motives?


    Norm
     
  11. eighty6gt

    eighty6gt forum member

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    3.73's in my car are factory Ford. They are the quietest. I was the last person to set these up, were the same before and after I touched them.

    The 4.10's in my fox were Ford racing. Shade tree mechanic did the job.

    I would try some motive gears if they are cheaper, I would set it up myself.

    Good luck!
     
  12. Juice

    Juice forum member

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    I do all my installs and have done several different ratios. I have not had any noise/whine with any of the ratios (2.73, 3.08, 3.27, 3.55,&3.73), provided I took the time to do the job roght. (No shortcuts lol) Always used Ford gears.
     
  13. 1950StangJump$

    1950StangJump$ forum member

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    I’ve had 3.73s and 4.10s that did not whine. That said, the chances of them making noise increases as the ratio goes up, ie 4.56 is more likely to make noise than 3.55.

    Also, install is not the only variable. The gears can be more or less noisy based on nothing more than luck from manufacturing tolerances. And, while Ford gears are generally considered better than Richmond or Motive, the truth is they are probably often (not always) the same manufacturer and simply rebranded. Just depends on when and where. These companies are constantly seeking our different suppliers to make the most profit.
     
  14. Norm Peterson

    Norm Peterson corner barstool sitter

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    Appreciate the help, guys.

    I'm leaning toward 3.73's to go with a 2.66/1.78/1.31/1.00/0.80/0.63 Magnum XL.


    Norm
     
  15. Juice

    Juice forum member

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    Im really liking the 3.73s and have put close to 20k on it since the swap.
    Just curious why did you pick the "wide" ratio magnom?
     
  16. Norm Peterson

    Norm Peterson corner barstool sitter

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    The 2.66-low Magnum is the close-ratio box (the wide ratio box is something like 2.97/2.10/1.46/1.00 with two overdrives). The overdrives I'm looking for are something of an option (basically the wide-ratio box's overdrives, which are closer to each other than the close-ratio box's overdrives are - go figure); the 2.66 low box normally ships with more widely spaced overdrives.

    What I'm looking for is a usable 2nd gear for coming out of 45-ish, maybe 50-ish mph corners and a 5th gear that doesn't fall on it face.


    Norm
     
  17. 1950StangJump$

    1950StangJump$ forum member

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    Update: The shop, JPC in Millersville, MD, has been outstanding. They truly live up to their reputation. Been dealing directly with the owner, Justin.

    Justin heard the whine. While he would have chosen to live with it (given it wasn't bad), they tackled it anyway because it bothered me. At first, they attempted just to adjust the gears, but that only made it whine on accel also.

    So, they then put all new 4.10s in for me . . . much better! We assume it was just the variance in the individual gear set. Both were FRPP.

    If I listen hard enough, I'm sure I could find a sound, but overall I'm extremely happy.

    P.S. Norm, when I decided to go 4.10 with the 2.97 Magnum, it was after much research. I knew that, with the TR3650 and 3.55s, I loved 1st gear at my power level, but needed 2nd and 3rd to be shorter while not making 6th too short. So, since mine is a street driver, I picked a typical RPM in which I would want to be able to goose the throttle and get good response . . . 2000 RPM. Went to Tremec's website and used their calculator to compare MPH at 2000 RPM with various transmission and gear combinations -- even made an excel spreadsheet so I could visualize everything. The theory worked in practicality perfectly; the car feels exactly like I want for my intended use. I recommend you do the same.