Rear-end gear ratio recommendations for my 79' Camaro?

Discussion in 'Transmission & Driveline Topics' started by 1979SportCoupe, Feb 21, 2021.

  1. FooFighter

    FooFighter Member Gold Member

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    I would go with what Twisted Metal and CorkyE said, they hit the nail on the head with the rear end gears. An overdrive transmission will make the car so much more drive able, especially at 55 mph and up.
     
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  2. Wolfman911

    Wolfman911 Member

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    I run a 3.73 gear in my car with a TH350 and stock tire size. With that I'm running around 4000 rpm at 70mph. My engine is heavily modified and it likes RPM's, so it works for me. But that would probably wear out a lesser built 350 if doing a lot of highway driving.
     
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  3. hd_cat

    hd_cat Member

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    The 3.42 is a great compromise, not bad on the highway, plenty of torque multiplication between stoplights. I had an '81 with the 2.56:1 differential gear, what a mistake. Our '73 and '79 are equipped with the 3.73:1, the '73 is a 4-speed, the '79 has a TH350 with a TCI 10" converter, both are very driveable, especially with the P275-60R15 rear tires. Keep in mind the tire rollout, the P275-60R15 is a bit of an overdrive with a 28" diameter. IMO, the 3.08 will disappoint, not enough torque multiplication!
     
  4. Cardinal

    Cardinal Veteran Member Lifetime Gold Member

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    When I got our 79 Camaro Berlinetta, the 3 spd manual trans and clutch were shot. I put a 700R4 trans in it out of a 30 Series Chevy Van that the trans had JUST been rebuilt by a VERY reputable local dealer but the 350 engine puked a rod!

    Here's a link to my post about the process of installing a 700R4 in a Gen II Camaro: installing 700R into my 73 Z28, Ideas ? | Page 2 | NastyZ28.com

    OBTW, our Berlinetta had a 10 bolt 3.08 posi rear that was in PERFECT shape. I forget what the final drive ratio of the drive line was in low gear but it would accelerate like it was a 3.73 rear but in overdrive it dropped the rpm's a lot!
     
  5. ruthlessz28

    ruthlessz28 Veteran Member

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    I got Th350 4.11 gears and a 275/60R15 tire 2400 stall converter not good at highway speeds. great in the 1/4 (11.1sec.) but around town 45mph=2400rpm forget 65-70mph for any extended amount of time.1 you'll go deaf 2 you can watch the gas gauge go down.
     
  6. Robert M Mrozek

    Robert M Mrozek Veteran Member

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    Last year I just changed my ratio from 4.56 to 3.42. Have a 1970 Camaro with 350 engine, TH-350 automatic, 18 wheels. Miss the beastly low end torque of the 4.56 gear but I feel the trade-off to be able to drive at 55-60 mph without feeling like the engine is gonna blow up is an easy trade-off. The car is much more drivable for my short cruises or going to the local car shows.
     
  7. K1ng0011

    K1ng0011 Veteran Member

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    I use the program on the site below. Put in enough numbers it will give you a better understanding on how gears in your rear end, transmission, and tire size all play together. This will probably get you in the ball park of whatever your doing, racing, cruising, etc.

    https://locost7.info/gearcalc.php
     
  8. Fbird

    Fbird Veteran Member Lifetime Gold Member

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    i seem to recall "back in the OLD days" the gear selection chart was
    1. List engine rpm where you are in your MIDRANGE of torque
    2. List tire size
    3. Pick gear so YOUR tire size puts YOUR motor RPM to cruise at 60 mph.....
    This was way back before OD trannys of course because it was solely based on 1:1 driveshaft rpm. Now this formula still works OK but most folks are NOT used to buzzing around at 3200 rpm at 60 mph when TODAYS cars run more like 1700 rpm at 60
     
  9. GoldenOne7710

    GoldenOne7710 Equal Opportunity Offender Lifetime Gold Member

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    I am not liking the 3.73 in my car these days. I want/need to upgrade the differential by dumping the GM G80 unit and installing something stronger. I'll likely swap gears to a 3.42 ratio when that happens.
     
  10. Fbird

    Fbird Veteran Member Lifetime Gold Member

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    not all OD trannys are equal!!!
    Automatic Transmission Gear Ratios

    1st 2nd 3rd 4th Reverse
    GM
    Powerglide 1.76 1.00
    TH350 2.52 1.52 1.00
    TH400 2.48 1.48 1.00
    200r4 2.74 1.57 1.00 0.67
    700r4 3.06 1.62 1.00 0.70
    4L60E 3.06 1.62 1.00 0.70
    4L80E 2.48 1.48 1.00 0.75

    That 3.06 first gear is quite a multiplier compared to 2.5 in the "old" stuff. As well as the 1.5 split from 1-2.
     

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