Highway Rpms

Discussion in '1965 - 1973 Classic Mustangs -General/Talk-' started by delmo408, Sep 22, 2013.


  1. delmo408

    delmo408 New Member

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    Time to fix up my '67 289 a bit more. I hate the fact I'm turning like 2600 rpm at low highway speeds with my c4. Would like to add an aod and leave the rear end alone (3.08). That will drop my hwy rpms to around 1700. Is that too low?
  2. rbohm

    rbohm Founding Member

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    the 289 likes to rev, so yes 1700 would be a bit low. better to shoot for more like 1900-2200 rpm at 65.
  3. delmo408

    delmo408 New Member

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    So then I'm looking at a new rear end. New gears vs. a cannibalized rear from something else? Any suggestions?
  4. rbohm

    rbohm Founding Member

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    actually you can just replace the ring and pinon gears in your current 8" with something like a 3.55 or 3.73 gear. currie enterprises sells them. and a 3.55 rear gear with a .67 overdrive in the AOD would put you rolling down the highway at 65 at just a tick over 2000rpm(2019 to be exact) with a 25.6" tall tire.
  5. delmo408

    delmo408 New Member

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    I like the 3.55 gearing. My "guy" says to just replace the gears will run me $1000. He suggested we replace the entire rear end with a salvage Explorer with either the 3.55 or the 3.73 gears. Says it will cost me less. Does that sound realistic?
  6. madspeed

    madspeed Colonel Mustard Mod Dude Founding Member

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    your guy is a ripoff
  7. valley82

    valley82 Member

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    Wow, send your third member to me I'll have the gears replaced and send it back to you for $900.00 and I'll make several hundred dollars on the deal! Find someone else he must be used to working on Italian sports cars.
  8. valley82

    valley82 Member

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    Last edited: Sep 24, 2013
  9. rbohm

    rbohm Founding Member

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    madspeed and the others are right, your guy is ripping you off big time with that quote, unless he is quoting for replacing the entire rear end with one from currie enterprises. the reality is that it should cost you about $400 total to replace the stock gears in your pumpkin, and that is him pulling the pumpkin from the car, getting and installing the gears, and putting the pumpkin back in.
  10. valley82

    valley82 Member

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  11. delmo408

    delmo408 New Member

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    I called another local company and they quoted me $850. Best I keep looking.
  12. rbohm

    rbohm Founding Member

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    you know, it isnt hard to replace the gears yourself if you want to. the hardest part is setting the preloads and the backlash. all you need though is a couple of specialty tools that are inexpensive, a beam type torque wrench and a dial indicator, and perhaps a set of dial calipers to measure the pinion bearing washers.

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