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4.10 or 4.56 ???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by bigjbear, Jul 17, 2000.

  1. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    Next weekend will be three in a row so I have just about enough cash saved up for my next project: gears and lockers. Thanks again to all who answered the locker post... Now for the next decision, 4.10s or 4.56s. Let me know what you've got and how you like it on the trail and the road. Here are my specs so we can compare apples to apples: 350/TH350C/NP205, 10 BLT/12 BLT, & 35x12.50-15 BFG M/Ts (they measure just under 34" mounted on my truck). Jim.

    BigJBear '80 GMC
    http://www.bigjbear.coloradok5.com
     
  2. Shawn

    Shawn 1/2 ton status Premium Member Author

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    With that t-case and tranny, I'd strongly recommend 4.56.

    Shawn
    87 K5
     
  3. Depdog

    Depdog 1/2 ton status Author

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    Hey you did not give him the (chanting 4.56) gear in the back ground. Yep, go with 4.56, I have never looked back or been unhappy. Well gas milage did not improve, did not really expect it to though.

    Depdog

    <font color=blue>"Lead, Follow, or BECOME the Trail"</font color=blue>

    http://depdogsk5.coloradok5.com
     
  4. Shawn

    Shawn 1/2 ton status Premium Member Author

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    I was afraid if I did the chanting, it might scare him off and he'd opt for the 4.10's instead...

    BTW- Do the gear calculator and you can see there's not much difference between the two ratios. On the highway, it's only a difference of 300.

    55mph:
    4.10= 2619 rpm
    4.56= 2913 rpm

    http://www.off-road.com/chevy/calc.html

    Shawn
    (chanting 4.56, 4.56, 4.56...)
     
  5. realsquash

    realsquash 1/2 ton status

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    You should look into the ORD doubler before you drop all your cash on gears. Obviously the doubler doesn't replace lockers, but you can run 3.73 axle gears and still get a good crawl ratio with the doubler engaged...

    Squash
    http://www.trailrunners4x4.org/users/realsquash
     
  6. loudandproud

    loudandproud 1/2 ton status

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    What do the different size gears do?
     
  7. Shawn

    Shawn 1/2 ton status Premium Member Author

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    No offense realsquash but I'd still rather have a desired gear ratio before the Doubler. Just driving around town here in Denver (mile high power robbing altitude) and heading up the Mountain highways is a pain with anything less than 4.10 and my 36" tires. Even with my big block, it struggles a little with the 4.10's but 4.56 would be more ideal. After shelling the cash for Doubler adapter, you still have to find a NP203 and get both shafts lengthened/shortened so it can a little expensive compared to gears. Don't get me wrong, I'd love to have a doubler but I think for driving around town and steep highways, gears are essential.

    Loudandproud- By changing the gear ratio, you can get better performance from your vehicle. For example, a drag car would want 4.56 or more since he wants to get the fastest time in the 1/4 where as if your trying to set a land speed record, then you'd want 2.73 or lower since your trying to achieve maximum mph. When it comes to a 4x4, you just want a ratio that matches your tires so the engine is running in the proper power band. If you install 44" tires and have 3.08 gears, your engine and transmission is going to have a hard time starting out from a dead stop let alone a steep trail. A 44" tire would require around 5.13 gears to match the factory gears that were designed for a 29" tire. Does this make any sense???

    Shawn
    87 K5
     
  8. loudandproud

    loudandproud 1/2 ton status

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    Bigger gear, better acceleration? Kind of on a 10 speed bike? Well what tire sizes and gear sizes go together? I think I am getting it.
     
  9. Shawn

    Shawn 1/2 ton status Premium Member Author

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    Yep, just like a bike just more expen$ive. It depends on what RPM you want your engine to run at and if you'll be on the highway or off-road. Here's my desired ratios for the tires but this is just my opinion:

    3.73 = 31"
    4.10 = 33"
    4.56 = 35" or 36"
    4.88 = 38" or 40"
    5.13 = 40" or 44"



    Shawn
    87 K5
     
  10. Cornfed-90K5

    Cornfed-90K5 Registered Member

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    go with the 4.56's they will bring your truck back to stock cruise rpm


    Cornfed-90K5
    1990 K5 Blazer
    1977 Jeep CJ5
     
  11. Moose

    Moose 1/2 ton status

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    I've been told to run 4.10 with my 383/sm465/205 tcase. 12 bolt rear. What do you guys think,
     
  12. Shawn

    Shawn 1/2 ton status Premium Member Author

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    Depends on your tires. I have a 454/465/205 combo with 36" tires and my big block struggles just a little going up steep hills at 55mph witht he 4.10 gears. 4.56 gears would put the RPM's in the proper power band.

    Shawn
    87 K5
     
  13. realsquash

    realsquash 1/2 ton status

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    Shawn, I agree with you on the gears, but I was just making sure that all options are explored. In my case, I have 4.10s/454/465/205 with 35" boggers (read: very heavy tires) and it cruises fine with 4.10's. But off-road I can engage super-low-low for crawling past the jeeps.

    I happen to know a lot of people around here that would almost give you the np203 with th350 adaptors! ORD shaft and plate would be required then.

    Ciao!


    Squash
    http://www.trailrunners4x4.org/users/realsquash
     
  14. loudandproud

    loudandproud 1/2 ton status

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    What do the numbers 454/465/205 mean? I am pretty sure the 454 is your engine, but what are the other two numbers?

    Thanks
     
  15. Shawn

    Shawn 1/2 ton status Premium Member Author

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    454 = engine
    465 = Muncie 465 4spd transmission
    205 = New Process 205 tranfercase

    Almost all transmissions and t-cases are geared a little different.

    Shawn
     
  16. ggallin13

    ggallin13 1/2 ton status

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    454 is the motor in cubic inches, the 465 refers to an sm465 which is a manual 4-speed tranny, and the 205 refers to the transfer case. All of these components work together and inter-relate, so with one set-up 4.10 gears might be better (like above) but in another 4.56 gears are desirable (overdrive tranny, for example).

    Consider where you do most of your driving when you go for gears. 4.56 gears give you stock performance with 35s, so if you do a lot of road driving that is the way to go. If you have the manual, you may want to go with 4.10s if you are on the highway a lot, as you have lower RPMs at cruising speed (overdrive helps this, hence 4.56s being better in that application). Of course, if there are lots of hills where you live, 4.10s may be too high and you may still want to go with 4.56s.

    On the other hand, if you wheel a lot (and I mean A LOT) then you can go with 4.88s and get an ultra-low crawl ratio, as well as amazing performance off the line at stoplights! [​IMG]

    The higher the number (that is, the lower the gears) the weaker they are, by the way. But if you want 4.88s or lower you are a crawl junkie and have 1-ton axles already probably[​IMG].
     
  17. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    Thanks guys, I think the chanting put me over the top. Well, that and seeing Dep's truck work the way it did. I just needed that extra push to go lower. It seems most people who have 4.56's are happy. Most of my driving is around town, about the only time I get on the Interstate is to get to the trails. Anyone else want to comment? Jim.

    BigJBear '80 GMC
    http://www.bigjbear.coloradok5.com
     
  18. i_4x4

    i_4x4 1/2 ton status

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    4.56's a MUST!!! I just put 56's in mine, and I have 305/th350/208. The R's are a little high do to that I'm only running 33's. But sure help's that little 305 alot.

    LET'S ROCK
    Don't follow me you will get STUCK!!
     

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