rearend gearing options

Discussion in 'Transmission & Driveline Topics' started by defiant1, Jun 27, 2013.

  1. defiant1

    defiant1 Member

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    has anyone tried a 3:08 gear ratio for the street. I currently have a 79 Z28 with the 3:42 open gears, automatic transmission. I am kinda wanting to get more of an interstate gear and lower rpm at cruise speed say 75 mph. It seems like the trans am had a 3:08. just looking for feed back please. Of course I will keep the factory gears in case I sell the car.
     
  2. rockheadrocks

    rockheadrocks Veteran Member

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    Many second gens came with 3.08 rear gears. My car, a 75 LT, came with a 350 4 barrel, 4 speed, and 3.08 open rear. With 255/60 R15 rear tires, it cruises on the highway at about 2400 rpm at 60 mph.
     
  3. chevy-stu

    chevy-stu Veteran Member

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    upgrade to an overdrive trans, it's much more worthwhile...
     
  4. Twisted_Metal

    Twisted_Metal Administrator Staff Member Lifetime Gold Member

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    ^+1

    I have a 200-4R with 3.42 rear gears.... 2000 RPM @ 70 mph.
    (final ratio = 2.28)
    20 mpg with the A/C on @ 70-75 mph. :D
     
  5. defiant1

    defiant1 Member

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    I really like the overdrive trans option although with a matching number trans case, engine block and rear end I hate to get to far from original.

    You know I had a 75 LT before my Z and it was real nice on the interstate. It was an automatic turbo 350 and I bet it had 3:08. I never verified it though.
     
  6. 351maverick

    351maverick full time Ebay seller/hustler/car killer

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    is 3.08 vs 3.42 really worth the hastle & expense?

    doesn't seem like much of a difference

    I went from 3.50 gears to 4.11s in a 79 F150 (36" Buckshot mudders...those were the days) and I almost couldn't tell a difference at all
     
  7. BondoSpecial

    BondoSpecial Veteran Member Lifetime Gold Member

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    3.08s with a low first gear 4 speed would make sense, but with an auto I'd just do a 700R
     
  8. big gear head

    big gear head Veteran Member

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    You could do a 200 4R without having to modify the cross member, drive shaft or anyting. If you do the rear end then I would recommend finding a 3.08 rear end and swap the whole thing. Then you can store your original rear end for when you want to put it back to all original.
     
  9. Skip Fix

    Skip Fix Veteran Member

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    2.73s use the same carrier as 3.08s and 3.42s if you can find a set. Lots of Pontiac guys dump their 2.41/2.56 carriers and gears too. Problem with those gears and a normal first gear is getting moving. My 79 Camaro had the 78 TAs 2.56 in it before we swapped in 3.73s. I swear it could idle at 25 mph in first!

    My 81 has 3.08s and still seems to be screaming at 70, especially when you are used to a daily driver with an OD tranny.
     
  10. Zspoiler

    Zspoiler Veteran Member

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    You can always run a taller tire first.I have 3:42 gears in my 1979 Z-28 Camaro I have run it as turbo 350 automatic ,and a 4 speed car both with P235 60/15 it cruised around 23-2500 rpm at 60. So try going to a P275 60/15 of which is a taller tire.And try that because its lot easier on both the pocket book and your back.And if you don`t like it. Its always easier to change it back.
     

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