1. Welcome to PlowSite. Notice a fresh look and new features? It’s now easier to share photos and videos, find popular topics fast, and enjoy expanded user profiles. If you have any questions, click HELP at the top or bottom of any page, or send an email to help@plowsite.com. We welcome your feedback.

    Dismiss Notice

gears

Discussion in 'Chevy Trucks' started by mikes plowing, Mar 3, 2008.

  1. mikes plowing

    mikes plowing Member
    from cent pa
    Messages: 77

    Any one tell me a easy way to find out what gears I have. Don't want to rip it a part if I don't have to. 87 blazer fullsize
     
  2. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    The easiest way is to look on the option tag in the glove box. If it's long gone or no longer legible, the second easiest way is:


    1) Jack up ONE rear tire until it's off the ground.

    2) Place two reference marks, one on the yoke and one directly in line with it on the axle housing with a paint pen or chalk.

    3) Place another reference mark on the tire. Either straight up or straight down.

    4) Place truck in neutral.

    5) Using your ref mark on the tire, turn the tire by hand TWO complete revolutions while counting the drive shaft revolutions (by your reference marks) as you go.


    How many times did the drive shaft turn?

    Slightly over 3 turns would be 3.08's

    Real close to 3 1/2 turns would be 3.42's

    3 3/4 turns would be 3.73's
     
  3. AbsoluteH&L

    AbsoluteH&L Senior Member
    Messages: 573

    Hope he doesn't have posi. :jester: JK
     
  4. ahoron

    ahoron Senior Member
    from here
    Messages: 422

    Option tag codes Gu2=2.73 gu4=3.08 gu6=3.42 gt4=3.73
     
  5. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Even if it did it would be a Gov-Loc if it's the original unit, which would still be able to turn at slow speed by hand.


    And if it has an actual clutch or cone style limited slip in it (aftermarket), you simply turn the tire ONCE instead of twice.


    Still easy..:)
     
  6. Duncan90si

    Duncan90si Senior Member
    Messages: 602

    Here is a complete list for those who are interested.

    Rear End Ratio RPO Codes
    GQ1 -- AXLE REAR, STD RATIO
    GT4 -- AXLE REAR, 3.73 RATIO
    GT5 -- AXLE REAR, 4.10 RATIO
    GU4 -- AXLE REAR, 3.08 RATIO
    GU5 -- AXLE REAR, 3.23 RATIO
    GU6 -- AXLE REAR, 3.42 RATIO
    G80 -- AXLE REAR, LIMITED SLIP (POSITRACTION)

    HC4 -- AXLE REAR, 4.56 RATIO
     
  7. mikes plowing

    mikes plowing Member
    from cent pa
    Messages: 77

    the only thing in the glove box is a tag with a hole list of # . Have to try the tire this week end thanks. What is the best gears to go with 33s
     
    Last edited: Mar 3, 2008
  8. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Depends on what engine and trans combo you have as well as the intended purpose you use the truck for the majority of the time in order to choose the ratio thats best for your specific application.

    305 or 350?
    Any engine upgrades?
    700R4?
    All purpose truck? ie: hiway driving as well as plowing.
    Or plowing only.
     
  9. mikes plowing

    mikes plowing Member
    from cent pa
    Messages: 77

    It has a 305, I changed the 700r4 for a 350 turbo. all kinds of driving. It's my only truck.
     
  10. mikes plowing

    mikes plowing Member
    from cent pa
    Messages: 77

    I checked and I have 308s in it. What can i go with.
     
  11. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    With a T-350 trans (no overdrive) and running 33's, 3:73's would be a good all around gear.
     
  12. mikes plowing

    mikes plowing Member
    from cent pa
    Messages: 77

    Thanks I wont to try and get them in this summer. Checked and it's going to run me $300.00 a axle to have them done.
     
  13. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    $300 each is a good price if your talking new gear sets and the usual seals...especially the front since the labor time is a bit more for disassembly.
     
  14. cjasonbr

    cjasonbr Senior Member
    from Mass
    Messages: 635

    axle code 31
     
  15. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    Do what I did, find a parts truck K20 with 8 lug 3:73 axles and swap the whole axles in. Then you won't have to worry about breaking those little axles and studs.
     
  16. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Nothing wrong with that of course but unfortunately 3/4 tonners don't help in the strength department enough in the front, since there's very little difference in front axles between the 1/2's and 3/4's.

    Would help with a gear change by making it more of a "bolt and go", but don't expect the front driveline to be substantially stronger.
     
  17. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    Well, the 3/4 axle stubs have a bit more beef than a 1/2. Not a lot more like a Dana 60, but I ran 35 and 36 inch tires on 3/4 corporates without any breakage. I've lined them up on the floor for comparison, the 3/4 is a tad thicker. Oughta be strong enough for 33s on a Blazer, without spending what it would cost to hang a D60 under there. And a full floating rear would help a lot more, that's where a good portion of the work get's done. And I don't have as much faith in six itty bitty 1/2 inch lug studs compared to eight big 9/16 studs. Not to mention bolt on drums, bolt in axles, bigger brakes, more unsprung weight keeping it rightside up.
    So to me, it's a very worthwhile conversion. Not to discount what you're saying, other than the outer spindles the axles are essentially the same. And as long as he never goes up over 33s the 1/2 ton ought to do fine.

    I put 36s on a 3:08 6 lug fulltime 4wd Chevy, took about a week to grenade the front diff.

    As to the bolt and go, that would be the biggest plus for me. I could swap out the whole axles faster than I could rebuild the gearsets.

    And lastly, 33s with a 3 speed are not going to be happy with 3:08s. 3:73s at a minimum. I've had 3:73s with 35s and wasn't happy, then 4:10s were all around perfect. I'd rather have the 700r4, you get a lower 1st gear and OD. My current truck has 4:10s and 33s, and a 4l80e, I've actually lost a noticeable amount of power, but I don't dare go to 4:56s.
     
    Last edited: Nov 9, 2008
  18. cjasonbr

    cjasonbr Senior Member
    from Mass
    Messages: 635

    by accident i posted that post. I was searching for info about my rear axle and didn't want to forget what the code was... i guess somehow i also pressed enter... oooops. Sorry.

    Pretty interesting stuff though.... swapping axles.
     
  19. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    That isn't a difference between a 1/2 and 3/4 ton...it's simply a diameter variation throughout the years the axles were used. Otherwise they're the same...same 297X U-joint, same 28 (10 bolt) or 30 spline (Dana 44) inner splines...as well as the very same 19 spline on the outer stubs, so they're is no actual increase in strength. All your gaining on the front is larger brakes and bigger/more wheel studs (as you mentioned) ...nothing more.

    And the slight diam difference on the stub isn't worth a strength advantage regardless. They'll break at the U-joint ears or at the necked down portion on the inner axle first. They always do.. :D
     
  20. IMAGE

    IMAGE Sponsor
    Messages: 1,741

    you know the front axles are the SAME from a k10-k20 right? The only difference is the outer part has 8 studs. The actual strength is the same because they use the same shafts and housing.

    Yes the 14 bolt rear is much stronger though then the 10 bolt.

    I've got a 14 bolt with 4:11's and a detroit locker sitting in the barn if anyone needs one...