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Gear ratio

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by mountainexplorer, Dec 1, 2002.

  1. mountainexplorer

    mountainexplorer 1/2 ton status

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    Ok, I know, the truck's one year too old to be asking this question here, but I have a 1968 Chevy 3/4 ton 2wd with a 307 and a 4 spd. We've had this truck for 22 years, it's sat for 8 years, and just last week, I got it on the road again.

    I had never driven it myself on the highway before, since last time it was licensed was 1994 when I was 13. It felt extremely low geared. I take it 4.10 and 4.56 gears were probably the two most common gear ratios of that era/year?
     
  2. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    3:73's and 4:10's were most common 4:56 were very rare/forums/images/graemlins/shocked.gif
     
  3. R72K5

    R72K5 Banned

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    nope, 4.56 is actually most common because it was std equipment in 3/4 and 1 tons of this era
    and are lots of dana 60 rears and eaton ho52 and ho72 rears out there with this 4.56
    and 4.10 was optionally available
    and 3.54 dana 60 came under the 396/402 trucks of this era

    check out the GM specs sheets for these years for the info

    4 speed usually got you 4.10, if its a dana 60 rear thne it will have a tag on a cover bolt, if its leaf spring rear then it is most likely a dana 60
     
  4. mountainexplorer

    mountainexplorer 1/2 ton status

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    It's the Eaton ho72 I'm pretty sure, and it's coil sprung. Seemed low geared to me, of course it has 9.50R16.5 tires (about equivilent to a rated 31" tire).

    When I was little, my mom, dad, grandpa and I all went on a trip down through California to San Diego, then back up home here to Spokane in this truck, back when it was our only truck in the mid '80's. At that time, it had 7.00-15 Cooper Bias ply tires on 15" split rims, which stood the same height or a little shorter than the 16.5's. Now, I can't imagine taking it on that long of a trip in it...at least not going over 55 mph.

    I would guess it has 4.10's, but when I eventually check to find out, if it has 4.56's, I wont be too surprised.
     
  5. R72K5

    R72K5 Banned

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    if you tell me original drivetrain that was instaleld in it from factory and all the M-codes and all the L-codes off the SPID lable of the govebox lid and the year and model of the truck then i can find out what was originally correct for that drivetrain and year and truck i have all the GM original specs sheets for 67-72 years blazers burbs pickups chassis-cabs stake-bed windshield-cowl 5-30 series models

    if its really a 3/4 ton- in which no K30 were built until 73, thne its got the 5200lb axle which is the H052 not the h072, there are no differences other than brakes between the two they are same, just like the difference of a regular 12 bolt rear to a big 10 12 bolt rear, just the brake is the difference,.

    now the H110 11,000lbs axle is a whole different animal and was optionally available on 67-72 30 series trucks but very uncommon/rare and have i think wierd 10 lug hubs and do have the parking brake drum on the end of the tranny like in the big 1/5 and 2 ton two speed rear axle grain trucks 40-60 series

    good luck
     
  6. mountainexplorer

    mountainexplorer 1/2 ton status

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    It's a 1968 3/4 ton 2wd. 307 V8, 4 speed.

    Heres some info I took off the truck.

    MODEL# CE20934
    04F51BA FRT&REAR SHOCK ABS
    04G50CA HD REAR SPRING
    04M20DC 4 SPD TRANSMISSION

    MAX GVW RATING 7500
     
  7. Chris_T

    Chris_T 1/2 ton status

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    Can't speak to the 4 speed, but if I recall, 3.73's were standard with the 307/TH350 combo in the 4x4s
     
  8. R72K5

    R72K5 Banned

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    and 350/th350/th400 combo and those engines with 4 speed too

    most the 6 cyl and the 307 with 3 on tree was 3.73

    big block was complicated and in 2wd only anyways til 73

    certain BBC/4 speed was 3.07 and some others were 3.54 and auto- I'd have to look up in specs
     
  9. u2slow

    u2slow 1/2 ton status

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    Here's a few I wrecked out:

    '60 1-ton had 235/4-spd and 5.12's in the Eaton.

    '62 3/4-ton had 283/4-spd and 4.56's in the Eaton.

    '66 1/2-ton had 292/4-spd and 3.73's in the 12-bolt.

    '69 3/4-ton had 250/4-spd and 4.56's in the Eaton.

    '68 3/4-ton had 327/4-spd and 4.10's in the Eaton.

    '72 3/4-ton (Longhorn) had 350/TH350 and 4.10's in the Dana 60.

    I think the Dana 60 was used when the Power-Lok was optioned, or lazier gears were desired - but not always /forums/images/graemlins/confused.gif

    The Eaton - H054 for SRW, and H072 for DRW - came with *only* 4.10, 4.56, 4.88, or 5.12. Some had the Detroit No-Spin (aka Detroit Locker).
     

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