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What gear ratio?

Discussion in 'The Garage' started by kgblazerfive, Feb 21, 2006.

?

What gear ratio

Poll closed Mar 3, 2006.
  1. 4:10

    12 vote(s)
    17.4%
  2. 4:56

    39 vote(s)
    56.5%
  3. 5:13

    15 vote(s)
    21.7%
  4. drive neked who cares about gear ratio

    3 vote(s)
    4.3%
  1. kgblazerfive

    kgblazerfive keymaster Premium Member GMOTM Winner

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    I have a 60/60 combo, 350/700r4/203/205 drive train, looking at running 35 to 37 or so tires. Opinions on gears cause the rears have 3:54 in them now and I don't think that will work. Daily driver with some offroad use not to much hard core just want the ability to if I need too. Like to keep some gas milage.
     
  2. KingDuramax

    KingDuramax 1/2 ton status

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  3. Blazenkiwi

    Blazenkiwi 1/2 ton status

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    Yo dude, I am doing the very same thing as you at the moment, have just lifted the truck (85 K5) 4 inches and have MT 36" in Baja Claws, mine is a turbod 6.2 diesel/ R700 trans and have the 3.42 ratio, I tried it after fitting and it was useless, the engine was barely turning at about 40 mph in OD and converter lock up on.
    I am now importing a set of 4.56 from randys ring and pinion (you guys have got it sweet over there in the States, we pay through the nose to get bits sent down here) as a friend had done the same thing here and used the 4.56 ratio which makes it ok for wheeling and pretty good on the highway.

    Good luck with everything dude hope it works out for ya
     
  4. BranndonC

    BranndonC 3/4 ton status

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    i say put it in 4:1 low and see how you like it now. with that doubler you dont need the gears you may think in the axles, and you can keep freeway speeds with higher gears
     
  5. trailblazr81

    trailblazr81 1/2 ton status

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    Go with 4.56's. With the OD it will be great for a DD. With 35's Its only a couple hundred over stock gears n stock tires. Ive run 4.56's with 35's using a th350 and 700r4. Its a good combo. But if you plan 37's and maybe down the road 38"+ you may want to look at 4.88's or 5.13. How much highway do you see??
     
  6. kgblazerfive

    kgblazerfive keymaster Premium Member GMOTM Winner

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    Alot of it is going to be around town and highway and stuff. I'm trying to condense my fleet so my Burb will be a DD/Tow truck /family camp vehicle. Thats why the 35-37 inch tires so I can still tow.
     
  7. trailblazr81

    trailblazr81 1/2 ton status

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    Then the 4.56's. They should give a close to stock cruising RPM. Thats hardcore when you have a doubler in your DD/tow vehicle. I would stay 4" with 35's. Thats what Im running and its a PIA loading a keg in the bed!! :D :haha: I keep cold beer on tap at home and do alot of hauling with my truck so I wouldnt go much taller.
     
  8. seschev3

    seschev3 1/2 ton status

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    Go with 4.88's. It will help with towing and you have od, so no problem.
     
  9. Jonny-K5

    Jonny-K5 1/2 ton status

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    how fast to you drive on the freeway? ive got 4.56,35's and a 700r4, my truck is happiest at 75. any lower and its under the torque band. i iwsh i went with 4.88. with a heavier burb, plus possibly having 37's, i'd go 5.13's.
     
  10. muddybuddy

    muddybuddy 3/4 ton status

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    i vote for 5.13s gear once, not twice if u plan on bigger later

    i was originally going to do 35's and was looking into 4.56's. in the end i said screw it and went with the 5.13s. before i got the truck running again i found myself with some 42's in my hands. i would have shot myself in the foot if i had gotten 4.56's
     
  11. trailblazr81

    trailblazr81 1/2 ton status

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    I just think 5.13's with a 35-37" tire that is a DD is too much. Too high RPM on freeway. The guy already has a trail rig.
     
  12. muddybuddy

    muddybuddy 3/4 ton status

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    mines a dd :p:

    if hes goin to go 37's i think 4.88s would be a good compromise. he is going to be towing
     
  13. Jonny-K5

    Jonny-K5 1/2 ton status

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    too much if you dont have overdrive. you'll still be under 3000rpm cruising 70-80 mph with 35-37's and 5.13
     
  14. jk3078

    jk3078 1/2 ton status

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    I voted 5.13's. The extra power for towing will be nice and there is still o/d for the freeway. I have been running 37's on 4.10's for a couple of years now and it sucks on the highway, but I do have a dog motor.
     
  15. skidpan

    skidpan 1/2 ton status

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    not to hijack the thread, but I am going to be running a mild sbc, with a sm465, 205, and 38 inch tires.. what should i look into for gears?
     
  16. trailblazr81

    trailblazr81 1/2 ton status

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    Maybe. But I have run 35's with 4.56's with a 700R4 and it felt like it was stock. So I dunno if I would want to bump that up by 500 RPM if I did alot of freeway. But its doable. If it didnt see alot of freeway 5.13's all the way. I do 3000 RPM blasts on the freeway weekly 50 miles one way. Both in my truck and my Mustang that has 4.10's.
     
  17. kgblazerfive

    kgblazerfive keymaster Premium Member GMOTM Winner

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    I would like to keep the rpm's in the mid two's either way I'm looking at new carriers also but I'm thinking 4:88 might be what I need
     
  18. 6.2Blazer

    6.2Blazer 1/2 ton status

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    The 700r4 with the OD top gears is the key to the decision.

    4.10's with 35" tires would be marginal on the highway as you simply would not have much, if any, power when in OD. Your gears would be 4.10 x 0.70 = 2.87 equivalent in OD. With 37's OD would most likely be useless. Nobody will ever tell you that 2.87 gears are ideal for the street with this size tire, so why waste your time? My last two trucks have had factory 4.10's and about 31-32" tires with an OD trans and I drove both of them to work on the freeway at 70+mph each day at around 2,500 rpm.

    You could live with 4.56's but it would be marginal, not much better than the 4.10's. The equivalent ratio in OD would be about 3.20.

    With 5.13 axle gears it would be equivalent to about 3.60 while in OD on the highway, or pretty darn close to your current gearing. If possible get the truck running with the current gears with the bigger tires and cruise down the highway with the trans in 3rd gear (or D....just not in OD) and it would be about the same as the 5.13's with OD. Again, I doubt anybody will tell you that 3.60 axle gears are ideal for 35-37" tires if you had a non-OD trans, or that your highway rpm would be too high.
     
  19. trailblazr81

    trailblazr81 1/2 ton status

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    yes this all works and makes sense, but you usually want you OD gear to be the low RPM cruisin gear to provide better mileage. Thats why its usually at 1900-2200 RPM in OD, to try n get some decent mileage while on the freeway. 2400-2800 RPM is more into the powerband but could be costing mileage. And odds are you will be downshifting at any hill anyways. So I guess it all comes down to what mileage you are looking for and engine output. If I was doing alot of freeway miles in a DD with small block I would want to stay at 2000-2200 on the freeway. If I just did short jaunts then 2500-2700 would be OK.
     
  20. jekbrown

    jekbrown I am CK5 Premium Member GMOTM Winner Author

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    I have 4.56s and a 700R4 and hardly ever use OD with 35s... go 5.13s. You're going to want them eventually anyway. Trust me.

    j
     

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