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Rear end gear ratios

Discussion in 'The Hokey Ass Message Board' started by Dave Pitts, Aug 25, 2010.

  1. Dave Pitts
    Joined: Sep 6, 2006
    Posts: 10

    Dave Pitts

    I need some info on gear ratios. I built a 32 coupe in which I'm running a 95' Ranger rear end. I believe it's an 8.8, up front is a SBC 305 .030 mild truck cam, Offy intake with 3 2GC Rochesters. My question is how to find the gear ratio, will it handle approx 130 to 140 MPH and do I need to go to a 327 or 350. Thanks
  2. If you can drive it @ 130 - 140 with even a 350
    More power to Ya !!!!!!!
  3. jetnow1
    Joined: Jan 30, 2008
    Posts: 1,536

    from CT
    1. A-D Truckers

    There are numerous places with the formula to tell you this but you will need your
    rear tire diameter
  4. Deuces
    Joined: Nov 3, 2009
    Posts: 18,540

    from Michigan

    Chances are, the Ranger rear gears are probably 3.73's or 4.10's if it was behind a 4 cyl. motor.... Maybe 3.55's if the Ranger had a V-6.. If your looking for top speed, I'd go with the 2.73 or 3.08 gears out back...
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  5. The real question is will you handle 130-140. Don't know what you're running for suspension but on the old suspension 100 is fast in a deuce coupe.

    That said its not likely you are going to squeeze that kind of speed out of the 305 without a lot of work. The Deuce is a brick. At the speeds you want you are fighting aerodynamics. But with the right gear, may an OD tranny, a lot of highway and a good stiff tailwind, you might just pull it off. The 305 is a low rpm mill unless built to turn a lot of Rs, limited by heads, lack of compression and in your case your choice of an RV cam.

    You're ranger would have been an OD truck so it should be a pretty low gear. Look for a tag on the rear to start with. if no tag put it up on blocks, turn the wheel by hand then count how many times the pinion turns for each turn of the wheel. Pinion 3 turns wheel one turn is 3:1 and so on.

    The only real way to be absolutely sure of your gear ratio is to count the ring and the pinion teeth. Now divide the ring by the pinion. That would be Ring/Pinion. So if your ring had 40 teeth and your pinion had 10 teeth the equation would be 40/10. you will come up with 4:1 or 4/1.

    The numbers here are just nominal I pulled them out of my hat for examples only.

    Note: non of this was said to throw water on your dreams just to give you a starting place for achieving them.
  6. 53sled
    Joined: Jul 5, 2005
    Posts: 5,819

    from KCMO

    You could have an 800 cubic inch motor. That has nothing to do with speed.
    Transmission? Gears? Tires?

    8.8 rear is likely a 3.73, very common. Your tires lets say are 28". With no overdrive, you need to spin your engine to 6300 rpm. With an automatic with no lockup converter, make it a cool 7 grand. No street small block will live through that for more than a quick blast. You need a good overdrive.

    With 31 inch tires it comes down to 5660 rpm, but with 28 inch tires and a .73 od, 4574 rpm. The sweet spot for a torqey 305 or stock 350.
  7. Deuces
    Joined: Nov 3, 2009
    Posts: 18,540

    from Michigan

    Ford does stamp the number of teeth of the gear set on the outer edge of the ring gear... Once you locate those numbers, grab a calculator and do the math..
  8. rhpope
    Joined: Oct 22, 2007
    Posts: 73


    If the rear end still has the factory tag attached to one of the bolts on the center cover, then that will tell what the gear ratio is. It is on the bottom line on numbers and will be the left most numbers next to the bolt. It is usually difficult to make out the first part of the number with out removing the bolt, but you usually know what it is by looking at the second two numbers because if it says 08, 27, 55, or 73, you know the first number is 3, so you have 3.08, 3.27, 3.55, or 3.73. If it is 79, then it is 2.79 and if it is 10, then it is 4.10. There is a space between the first number and the second two numbers, so if it is blank, then it is an open differential. If it has an "L" in the space, then it is a limited slip differential.

  9. Hey mine does. I try to shift @ 6200 but I'm just not fast enough on the draw sometimes OK most times. :eek:
  10. 53sled
    Joined: Jul 5, 2005
    Posts: 5,819

    from KCMO

    Yours isn't exactly stock though, Ben. :)
  11. tgabbe1934
    Joined: May 20, 2009
    Posts: 64

    from smithtown

    You should probaly run 3:08's or 3:23's, I have 373's in mine. It is a blast to drive, very quick acceleration but on long trips it's abit much on the highway, turns to
    many rpm and really limits your mph! I wish I had a quick hange or a gear vendor!
  12. larry k
    Joined: Feb 23, 2009
    Posts: 307

    larry k

    just so you will know , i own a 32 with a 350/350 in it and had to go to a 273 rear from a 355 rear to get the rev's down .. with that said !! you really got some long legs so 130 mph ain't out of the question, but at 110 mph the car handles like a safe in wheel barrow, i ran out of balls ,before i ran out of mph !!! so you got my respect if you can hold it at that speed,? good luck on your first try
  13. hope you have good medical insurance
  14. fiveohnick2932
    Joined: Mar 29, 2006
    Posts: 889

    from Napa, Ca.

    I have about a 350 hp 383 BB mopar in my truck and I run 2.75 gears. Its nice first and second gear around town and 3rd is like an overdrive. It loves the freeway and has no problem doing 100 mph even in 2nd gear. dont expect it to throw you back in the seat like 4.10's but its still really fast! When the guys with 4.10's start to run out of gear the 2.75's are just starting to get it on.
  15. zzford
    Joined: May 5, 2005
    Posts: 1,822


    Yah-hunh ^^^^^what he said^^^^^ If you have big enough balls to drive one of these cars that fast, your balls probably won't fit in the car. :D
  16. Untame
    Joined: Jan 5, 2011
    Posts: 214


  17. AnimalAin
    Joined: Jul 20, 2002
    Posts: 3,417


    Rules of thumb that just happen to work out from the underlying mathematics:

    1. If the rear gear and tire height are the same, you get about 2000 rpm at 60 mph (i.e., 3.00 gear and 30 inch tire).

    2. If you use a 30 inch tire, the engine rpm at 90 mph will be the same as the gear ratio (i.e., 3.50 gear needs 3500 rpm at 90 mph).

    Hope these help you figure out what you need.
  18. GassersGarage
    Joined: Jul 1, 2007
    Posts: 4,729


    I had 3:00's in my '32. Running tri-power with progressive linkage, I decided to floor it on the freeway early one morning to use up the gas in the end carbs. I glanced at my speedo and noticed it was on 120. I shocked me because, like others have said, a '32 is a brick. It handled pretty good at 120, but she's fenderless.

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