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.

Gearing...

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by Topdown, Dec 15, 2002.

  1. Topdown

    Topdown 1/2 ton status

    Joined:
    Nov 26, 2002
    Posts:
    2,598
    Likes Received:
    0
    Location:
    Vancouver, Washington, U.S.A
    Ok... I finally got the tach installed in topdown. When I bought him the tweak I got him from had a butt-load of extra stuff for the blazer that he "never got around to putting in/on". Needless to say I had to throw 95% of it out, most of it was useless, rusty, or just plain crap.

    Anyway... the point here is that I found 2 sun supertach II's in the pile of refuse that he gave me and told myself "one of these has to work". Wrong. Neither worked. However, when I took them both apart and put the pieces of both together I got one working and finally installed it!!

    Here is the good/bad/question part. The first thing I did was start running some tests to find out what gears I am running. With the 32" tires I run 2000 rpm @ 50 mph... calculated out comes to 3.08 gears. So, when I replace the gearing... should I go with a 3.44 or a 3.73? I use this as a daily driver and do make some long freeway trips in it. I am not going to go any larger than a 33" tire (when my new 32's wear out). Off-road I usually run 4-Hi and dont typically do much rock crawling. Beach/sand is common as are deep ruts and decent amounts of mud and water...

    So... now that I have put everyone to sleep... anyone have any thoughts?

    Thanks!
    -Ryan /forums/images/graemlins/k5.gif
     
  2. Muddytazz

    Muddytazz 1 ton status

    Joined:
    Jun 30, 2002
    Posts:
    20,073
    Likes Received:
    0
    Location:
    Salem, Or.
    IMO, if your planning to eventually go with 33's, I'd go with 3.73's
     
  3. naranja72

    naranja72 1/2 ton status

    Joined:
    Jan 6, 2002
    Posts:
    110
    Likes Received:
    0
    Location:
    vancouver, bc, canada
    here's a link to try out: web page

    hope this helps,

    Marc
     
  4. Topdown

    Topdown 1/2 ton status

    Joined:
    Nov 26, 2002
    Posts:
    2,598
    Likes Received:
    0
    Location:
    Vancouver, Washington, U.S.A
    Thank you both for the input... I was leaning toward a set of 3.73's but wasnt sure.

    Thanks!
    -Ryan /forums/images/graemlins/k5.gif
     
  5. topjimmy

    topjimmy Registered Member

    Joined:
    Feb 20, 2003
    Posts:
    9
    Likes Received:
    0
    Location:
    Glen Burnie, MD
    Hey, i'm planning a gear swap as well...i was leaning toward 4.10's. i have 35's, don't do serious wheelin'...the chart just confirmed my choice...THX!!! /forums/images/graemlins/cool.gif <font color="blue"> </font> /forums/images/graemlins/thumb.gif /forums/images/graemlins/k5.gif
     
  6. Topdown

    Topdown 1/2 ton status

    Joined:
    Nov 26, 2002
    Posts:
    2,598
    Likes Received:
    0
    Location:
    Vancouver, Washington, U.S.A
    after much debate and thought, I believe I will be going with the 4.10's (can someone tell me the real difference between a 4.10 &amp; 4.11? I see them both used regularly)

    Thanks for all your help everyone!
    -Ryan /forums/images/graemlins/k5.gif
     
  7. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

    Joined:
    Mar 5, 2001
    Posts:
    15,680
    Likes Received:
    1,391
    Location:
    642 Days to BB2018
    Ryan,

    I wouldn't trust the tach to help you determine your axle gears!! ......you aren't doing that are you?

    HEI and AT tranny slippage can make the numbers less than accurate when comparing a chart of RPMs to actual measured RPMs

    You should really be safe and pull one of the diff covers and look at the ring stamping to get the correct tooth counts so you know FOR SURE that you have 3.08s or whatever....
     
  8. R72K5

    R72K5 Banned

    Joined:
    Mar 5, 2001
    Posts:
    8,905
    Likes Received:
    0
    Location:
    central IL
    [ QUOTE ]
    after much debate and thought, I believe I will be going with the 4.10's (can someone tell me the real difference between a 4.10 &amp; 4.11? I see them both used regularly)

    Thanks for all your help everyone!
    -Ryan /forums/images/graemlins/k5.gif

    [/ QUOTE ]

    different tooth count on the gears, 4.11 typically seen in gm corp 12 bolts and 4.10 typically seen in 3/4 and 1 ton eaton/gm corp axles

    same deal with 3.07 vs. 3.08 ratios- 3.07 usually only seen in the 8.5" 10 bolts and 3.08 usually seen in the 7.5" 10 bolts, tooth count on gears differ between the two ratios
     
  9. Steve_Chin

    Steve_Chin 1/2 ton status

    Joined:
    Mar 6, 2001
    Posts:
    1,126
    Likes Received:
    0
    Location:
    Foster City, CA, USA
    A 4.10:1 ring and pinion setup will have 41 ring gear teeth and 10 pinion gear teeth. A 4.11:1 setup will have 37 ring gear teeth and 9 pinion gear teeth (technically, 4.1111...:1). The gear you'll find in the 12-bolt truck rear would be a 41:10 setup. Most aftermarket suppliers also make 41:10 setups in lieu of 37:9 setups.
     
  10. chulisohombre

    chulisohombre 1/2 ton status

    Joined:
    Apr 11, 2002
    Posts:
    4,137
    Likes Received:
    14
    Location:
    Bangor,Pa
    stock gearing on early 5k's was 3.73:1 wasnt it?i always thought thats what all first gens had.i've had 3 different 12 bolts from 72 blazers.and they all had 3.73 gearing.
     
  11. LKJR

    LKJR 1/2 ton status

    Joined:
    Apr 18, 2000
    Posts:
    2,116
    Likes Received:
    0
    Location:
    Lubbock, Tx
    most likely if your running stock you probably have 3.08's in that 10/12 combo.
     
  12. Chris_T

    Chris_T 1/2 ton status

    Joined:
    Mar 17, 2001
    Posts:
    718
    Likes Received:
    0
    Location:
    Saskatoon, SK
    In a first gen it's a Dana 44 and a 12 bolt, not a 10 and my stock geras were 3.73 (with a 307ci and TH350)
     
  13. Steve_Chin

    Steve_Chin 1/2 ton status

    Joined:
    Mar 6, 2001
    Posts:
    1,126
    Likes Received:
    0
    Location:
    Foster City, CA, USA
    chulisohombre, it depends on the original engine configuration. 350 trucks got 3.07:1 axle setups as base (3.73:1 optional). 307 trucks got 3.73:1 axle setups as base. GM deemed the switch to 3.07:1 for the 350 as acceptable because of the additional torque the 350 has over the 307 (and, in doing so, they raised the CAFE ever so slightly).
     

Share This Page