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are 2.79 gears that boggy?

Discussion in 'Engine and Drivetrain/Mechanical' started by 67resto-coupe, Aug 27, 2010.

  1. 67resto-coupe

    67resto-coupe Member

    ok, so the roller 5.0 is running smoothly...got a new 2.5" x-pipe exhaust with spintechs....yet i'm not "feeling" that this is what 86-93 5.0 should feel like.
    i had expected a bit more of a surge when i get on it, but can my stock gearing really be that slow?
    i remember driving this car at 16yrs old....couldn't even get it to barely leave a stripe with the orig 289 and holding the brakes...
    but with a new roller, E-303 cam, etc, etc, i can leave a little stripe on command, but i expected more.

    i imagine i may be leaving a bit out from tuning, but overall, is the gearing really affecting it that much?

    i also have a tci torq converter in the c4 and i can't go beyond 3.23s according to the box. would 3.00 or 3.23's make that much of a difference over the stock 2.79's?

    p.s. i plan on running 17" wheels if that makes any difference....thanks.
     
  2. daveSanborn

    daveSanborn Active Member


    Yes, they are. They're designed to improve fuel economy, not performance.

    I'm not sure about your TqConv warning, but I'd have no problems stepping up to 3.25/3.50 gears to improve your acceleration. Understand that your top end speed will suffer as you improve acceleration. AOD's and T5's are geared better for 3.25/3.50 than your C4 is.
     
  3. apollard

    apollard Active Member

    In HS, I had a '67 with a straight six w/ auto. I blew the rear end out of it, and went to the junkyard and pulled one from a manual car. That took me from a 2.79 to a 3.25 gearing. The difference was incredible - I could keep up with my buddy's 289 2bbl car easily, and after decent exhaust and tune, out run him. So, I'd say moving to just a 3.25 would help quite a bit.

    The gas mileage took a good sized hit, though.
     
  4. blue65coupe

    blue65coupe Well-Known Member

    Ditto. Step up the gear. If you're gonna be doing a fair amount of highway driving I'd go with the 3.25. I've got a 3.55 in mine with a c4 and it pushes over 3K at 70 mph. If I had it to do over I would've went with a 3.25 or ran a 3.55 with AOD.
     
  5. Starfury

    Starfury Active Member

    I swapped from 2.79's to 3.25's a couple years back. The difference was huge. The gears made more difference in my butt-meter than my entire stroker rebuild, which added a good 100hp to the motor.
     
  6. RustyRed

    RustyRed Active Member

    In a word, yes. In two words, big yes.

    I had built the motor on mine (302, ported GT40's, mild cam, holley 600, etc) and upgraded my transmission with higher stall, B&M shift kit and my car was still very sluggish off the line. You'd have thought I still had the worn out 289 with 2 barrel we had pulled out of the car.

    Got po'd about it and ordered the Currie posi third member with 3.55's.

    Night and day difference. When you punch it now you feel the wheels grab immediately and seems to have a lot more snap with less wasted energy.

    Makes the car run at higher rpm's on the freeway but I don't drive on the freeway much so I don't really care. However, I am considering upgrading to a larger aluminum radiator due to the higher rpms when running say 45 - 50 mph.
     
  7. camachinist

    camachinist Member

    LOL, more likely *below* 3.23 numerically, due to the propensity for constant slip and subsequent heat/wear. You can run 5.67's with that converter; it could care less.

    If you drive the car all the time, 3.25'ish would be my advice. Weekend cruises and blasts, 3.50's. I drove my '67 to college, work, street raced and drove to the track, all with 3.50's and an 11" converter, this back in the 1970's. It was perfectly fine on the freeway, but I was a kid and didn't care about 'driveability'.

    Have fun!
     
  8. 70_Fastback

    70_Fastback Hell Bent for Speed Staff Member Moderator

    I am running 3.80 gears with my C4 - and it's horrible for the highway. I need a 4th and 5th gear.

    It boils down to your main intentions with the car though...
     
  9. jonward786

    jonward786 Member

    Good lord, i bet those 3.8s are fun stop light to stop light tho
     
  10. blue65coupe

    blue65coupe Well-Known Member

    He needs it to offset the effects of the scoop.
     
  11. Anonymous

    Anonymous Guest

    Pansie, I run 4.11's and drove it to Topeka and back, 140 miles @ 8mpg and a 4 speed.
     
  12. RustyRed

    RustyRed Active Member

    My car runs decent at 55 - 60 mph with the 3.55's.

    Granted, I am running close to 3,000 rpm but it hums right along. I have not tried to calculate my miles per gallon but I figure I probably don't want to know and since it's not a daily driver...who cares.
     
  13. Starfury

    Starfury Active Member

    Close to 3k? lol. I cruise in my 331-powered '67 at 3300rpm @ 70mph with 3.25's. I'm considering 3.93's or 4.11's now that I have a short-ratio toploader installed. First gear is a dog...
     
  14. RustyRed

    RustyRed Active Member

    The changing out isn't the problem, getting the speedo to read the right speed is the problem I've had.

    When I had my 2 point something stock rear end I was running an 18 tooth driven gear. Went up to a 20 tooth based on an online calculator and it was still way off. I changed out again to a 23 tooth that they advertise as being for a 4.10 rear...it's close now but still reads about 5 mph faster then I am actually going. I can't find a gear with more than 23 teeth so I guess I'll have to live with that.
     
  15. Anonymous

    Anonymous Guest

    might need to change the drive gear in the tranny.
     
  16. RustyRed

    RustyRed Active Member

    That had occurred to me but at only 5 mph off...it's a lot easier to just adjust the speed in your head. :5
     
  17. Anonymous

    Anonymous Guest

    I agree! I have the other drive gear to install in my toploader, but I'm not taking it apart unless I have a better reason!
     
  18. RustyRed

    RustyRed Active Member

    I've seen a deal that screws onto the cable that will slow down the reading 15% or 28%...but they are a little under $100 before shipping which also made me think I can live with 5 mph, LOL!
     
  19. 70_Fastback

    70_Fastback Hell Bent for Speed Staff Member Moderator

    Use a GPS to monitor speed.
     
  20. blue65coupe

    blue65coupe Well-Known Member

    It also screws up your odometer. For every mile I'm reading 1.2
     

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