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3.08 to 4.11

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 85k5blzr, Mar 21, 2001.

  1. 85k5blzr

    85k5blzr 1/2 ton status

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    I was wondering how much lighter the wallet is going to be after having new gears installed. I am running 32s and want to upgrade to 4.11s from my 3.08s with a posi in the rear. I was also wondering what the damage to my gas mileage would be? I currently get about 8 miles to the gallon city, 11 highway.

    85 k5 blazer with an old 305....must have more power! [​IMG]
     
  2. HispanicPanic

    HispanicPanic 1/2 ton status

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    ok here it goes i had 3.08 and went to 4.10 your city milage will get alote better but your highway milage will get worse and i run 33inch tire before and after you will love your top end and first gear price 500.00 for gears front and rear with master install kit posi is about 350.00 install should be about 350.00 if you plan on going 35's and are conserned about milage stick with 4.10 cuz thats what im gonna do but i have a th350 trannny i dont know what you have if you have overdrive go 4.56 hope the HispanicPanic helped you out check my jimmy out at jimjim.coloradok5.com its the orange one you cant miss it
     
  3. lowlevell

    lowlevell 1/2 ton status

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    I went from 3.42 to 4.10 with 31" tires (for now) and the 700r tranny. I noticed an imediate change, especially at low. BUT, it wasnt as much as i thought it would be. You should shop around for the gears and try to find a mechanic that will do this for you on the "side". I didnt regear, i re-axled :).

    One From None
     
  4. CaptCrunch

    CaptCrunch 1/2 ton status

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    yeah, if you don't have the knowledge and tools to do it yourself it will be cheaper to find some new axles... I'd say go 3.73's unless you are going to step up to 35's... 32 or 33's w/ 3.73's seem to give terrific gas milage... probably much better then you 3.08's...ick. W/ OD (assume w/ an 85 you do) it should be excellent off the line because the 700R4 already has a steep first gear and the OD on the freeway should send the rpm's down towards the 2100 powerbands range. Heck I upgraded to a Dana 44 and 12b w/ 4.10's for $500... once I get the brakes, seals and one shock mount fixed up will be about $650 total...[​IMG]. If you don't mind 10B's and don't beat on them you can find 3.73 sets for aslo as $250!

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     
  5. Wheels

    Wheels 1/2 ton status

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    Just did the 3.08 to 4.10 gear swap. $500 for the gears and master install kit from Drivetrain Direct. Did the install myself. Priced around and the rear was $250 and the front was $350 (more parts on the front to disassemble) to install. The install of the posi will not make a difference in price except the cost of purchasing the unit. They have to tear down the carrier to put the new gears on anyway. All totaled, about $1200 to $1300 for a complete gear swap (includes consumables like gear lube, gaskets, etc). With 33" tires, i was turning 2550 RPM at 70 MPH. After the swap, I'm turning 3200 RPM at 70 MPH. I'm just about done with a TH350/NP203 to 700R4/NP205 swap. This will drop the RPM down to 2200 at 70. I have a 25 mile commute everyday to work and some of the places I go wheeling is from 110 to 600 to 1400 miles away (need the overdrive). If you dont plan on swapping out the TH350, I would go with 3.73 as a good medium.
     
  6. 85k5blzr

    85k5blzr 1/2 ton status

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    I have a 700R4 tranny and a friend of mine who is a mechanic kept telling me that it would cut my gas mileage by 1/4. I don't plan on going over 33"s and was trying to keep the cost down as much as possible because i don't really trust myself to do it and being in school, having a limited income.

    85 k5 blazer with an old 305....must have more power! [​IMG]
     
  7. 85k5blzr

    85k5blzr 1/2 ton status

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    thanks for all the help

    85 k5 blazer with an old 305....must have more power! [​IMG]
     
  8. RESTORE89

    RESTORE89 1/2 ton status

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    about 2 weeks ago i had new gears installed in my 89 350 tbi 700r4, and i was getting about 13-14 mpg on the highway, with 33-12.50's. My ratio in the rear was so high i could not use overdrive and cruise at the same time, now with the 4.11's i am getting almost 17 mpg on the highway at 70+mph. i notice a big inprovement in the low end torque. i bought my gears from randys ring and pinion, gear app 150 a set US GEAR sets, 60 a set for the install kit, 300 for a lockright, that i had installed in the front. labor here is about 400 per axle. i have aboout 1500 in mine. i own 5 trucks, for my company, and i do most of my own work, and have a friend who is a life long mechanic, and i would not even do my own gear sets. it is wise to leave that to the guys who know best. after looking back, i wish i would have spent that money on a whole axle swap to a 12 or 14 bolt set up. live and learn
    good luck
    chris
     

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