Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

tire size/axle ratio RPM calculator needed,

Discussion in 'The Garage' started by R72K5, Aug 8, 2005.

  1. R72K5

    R72K5 Banned

    Joined:
    Mar 5, 2001
    Posts:
    8,905
    Likes Received:
    0
    Location:
    central IL
    with 31" tall tires and 4.57 axle and 1:1 ratio final gear in a manual trans what would cruising engine RPM be at 55 and at 65 ?

    trying to see if am gonna need taller tires to keep RPM down to where the truc can be driven long ways on freeway continuously without hurting old 350 engine

    what do you thnk is safe RPM to stay under for extended periods

    thanks
     
  2. randy88k5

    randy88k5 1/2 ton status

    Joined:
    Nov 8, 2004
    Posts:
    1,248
    Likes Received:
    0
    Location:
    Lynchburg, VA, USA
  3. R72K5

    R72K5 Banned

    Joined:
    Mar 5, 2001
    Posts:
    8,905
    Likes Received:
    0
    Location:
    central IL
    looks like 3221 RPM is what it would be running at 65mph

    would that be bad for extended periods of time with an old high mileage 70's 350 ?

    thanks
     
  4. txfiremank5

    txfiremank5 1/2 ton status

    Joined:
    Jul 6, 2004
    Posts:
    3,105
    Likes Received:
    0
    Location:
    San Antonio, TX.
    Yeah, that's a bit much in my opinion.

    I'm going to see if I can post this table directly. If I can, it's for a 1:1 ratio. Higher RPM's for autos, and lower for auto's w/ OD.

    ratio-table.JPG
     
  5. R72K5

    R72K5 Banned

    Joined:
    Mar 5, 2001
    Posts:
    8,905
    Likes Received:
    0
    Location:
    central IL

    yep it shows thanks im saving that one :D

    also manual trans be lower RPM too,- than autos anyways(of identical range ratio)


    thanks :thumb:
     
  6. sandawgk5

    sandawgk5 3/4 ton status

    Joined:
    Oct 28, 2003
    Posts:
    6,881
    Likes Received:
    1
    Location:
    Kitsap County PACNORWEST
    This is the best RPM calculator I have found and it is pretty darn accurate also.

    RPM Calculator
     
  7. R72K5

    R72K5 Banned

    Joined:
    Mar 5, 2001
    Posts:
    8,905
    Likes Received:
    0
    Location:
    central IL
    thanks :D
     
  8. R72K5

    R72K5 Banned

    Joined:
    Mar 5, 2001
    Posts:
    8,905
    Likes Received:
    0
    Location:
    central IL
    2700 and 3200 rpm, 55 and 65mpg with the 4.57 and the 31" tires

    looks like i need to dump the 4.57 junk and find a 4.10 third member for this eaton axle

    or just 14 FF it, 3.73 or 4.10

    i cant be running those RPM's with an old 350 like this, it wont last



    thanks :D
     
  9. txfiremank5

    txfiremank5 1/2 ton status

    Joined:
    Jul 6, 2004
    Posts:
    3,105
    Likes Received:
    0
    Location:
    San Antonio, TX.
    It, and others can be found here at:

    4lo.com

    They are on the left side in the menu.
     
  10. divorced

    divorced 3/4 ton status

    Joined:
    Jul 20, 2004
    Posts:
    5,115
    Likes Received:
    0
    Location:
    .

Share This Page