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gear ratios?

Discussion in 'The Garage' started by 88-3/4t-bad boy, Aug 16, 2006.

  1. 88-3/4t-bad boy

    88-3/4t-bad boy 1/2 ton status

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    well i was looking at 4 wheel parts gear ration chart. it says that for best fuel economy and highway driving (which i mostly do bc i lve out in the country) i should go with 4.88. but is that the best possible gear for it. or is 5.13?
     
  2. smokkey1

    smokkey1 1/2 ton status

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    what tranny? and what size tires do u have?
     
  3. 88-3/4t-bad boy

    88-3/4t-bad boy 1/2 ton status

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    oh. um i dont know the tranny. its a 3-speed with a low gear. and its a 3/4 ton sub if that helps? im going to go with 41" iroks.
     
  4. b454rat

    b454rat 1/2 ton status Premium Member

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    Divide 41 by your current sneaker size, then multiply by your current gear ratio. If you like you current gears, this will give you the eqvuilant with the 41s.
     
  5. 88-3/4t-bad boy

    88-3/4t-bad boy 1/2 ton status

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    yeah. how do you find out your current gear ratio? im a noob and i just started working on the truck.
     
  6. broncoman6524

    broncoman6524 1/2 ton status

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    alright if youve got an open or limited slip rear end. jack up on side tire, so its off the ground. chock a front tire. put th t-case and tranny into N. mark the tire position on the ground and tire and also mark on the pinion thingy on the axe (driveshaft enter place) rotate the driveshaft and count the number of times it take to, rotate the tire one entire rev. EX for every 1 time you rotate the tire your driveshaft spins a litte bit more than 3xs. that would be 3.08ish gears.

    what axle do you have this will make a huge difference in finding out your current gears. for you tranny you prob have a th400 or th350.
     
  7. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Pull the covers, the numbers are on the edge of the ring gear.

    Also, if you're planning on tires over 36" or so you should look into upgrading your diff's before you bother swapping in new gears. An 88 3/4 ton Sub would have a 10 bolt front and a 14 bolt semi floater. The 14SF should be fine up to 38's or so, but the front 10 bolt isn't gonna live if you wheel it.

    Anyways, for that tire size with an SM 465 I'd run 4.88's or 5.13's. Use one of the hundreds of gear calculators out there to find your rpms...

    Rene
     
  8. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    A "3 speed with a low gear" is a SM 465...

    Rene
     
  9. broncoman6524

    broncoman6524 1/2 ton status

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    :doah: im a tard...i thought i read auto somewhere in there...:o
     
  10. K5er4Life

    K5er4Life 1/2 ton status

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    How much streeet vs. offroad driving do you plan on doing. To me for any rig that sees mostly dirt there is only one ratio....5.13, or lower if you dont have a 14 bolt because you cant get any (numercially higher) gear sets for the 14 bolt. But if your truck will be doing alot of road driving then go with the 4.88's. Either way it doesnt really matter a whole lot really, your only talking a few hundred rpms either way. It works out to be like 2700 rpms at 65mph with 5.13 and 2500 rpms at 65 with 4.88's. One can never go wrong with 5.13's and a detroit......mmmmm.....say it now, detroit.

    oh by the way, I know theres lower gears for the 14 bolt ff, Randys ring and pinion does carry 5.38's now. But whatever, do what you think will suit your driving style best.
     
  11. 88-3/4t-bad boy

    88-3/4t-bad boy 1/2 ton status

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    yeah. i was thinkin 4.88's anyways. im getting a locker in a couple of months. but i was reading off road mag. or whichever one has the top truck challenge. anyways. trustyk5 said that 38's should be around it for the 14 bolt. but most of the guys in top truck challenge have 14 bolt gm axles on their rigs and 44's to 49's. and they wheel the hell out of their rigs. just wondering why you should only be fine up to 38's im trying to get the biggest yet decent tire for my wheels. they are outlawII's they came with the truck. havent checked but im pretty sure the are 16x8's. and so the 41" iroks looked like some scrumptious meat. wait... that didnt sound right. :blush:
     
  12. broncoman6524

    broncoman6524 1/2 ton status

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    you have a SF14b they run FF14b diffeence is yours is 3/4 ton and theirs is 1ton. IE theres is stronger and more beastly.
     
  13. muddybuddy

    muddybuddy 3/4 ton status

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    yep they are running full floats, youve got a semi-float....big difference

    i love my iroks, for the street they are awesome i didnt even have to balance mine and ive got bias. trails they are great, mud could be better but you gatta make compromises
     
  14. 88-3/4t-bad boy

    88-3/4t-bad boy 1/2 ton status

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    oh. ok. yeah. i knew the whole ff thing. but the fourwheeler mag didnt say that. just said 14 bolt gm. kinda skipped my mind. happens to often. yeah. im going to order some radial iroks very soon and im mostly on the highway more than off-road and i heard how good they were on road so i thought wth
     
    Last edited: Aug 18, 2006

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