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rear end gone

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by tecton, Feb 4, 2004.

  1. tecton

    tecton 1/2 ton status

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    started lockin goin around turns today quite a bit...then pulling out of a subdivision i give it some gas and it just stops going and grinds...i idle off the road...

    so...rear is trash.

    think i should just have them throw in a 3.42, or would id be fuel effecient to step up to 4.10 (might as well, wanted to for a while)?

    ive got 33's
    700r
    350
     
  2. Me89'Jimmy

    Me89'Jimmy 1/2 ton status

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    i assume youve got 10 bolt axles front and rear, odds are youve got one of the many many many factory gov locks that has crapped out. go for the 4.10s and if your in the mood for it throw in a posi, you'll thank yourself down the line, eaton sells an affordable upgrade of the gov lock, only difference is this one actually works /forums/images/graemlins/thumb.gif
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    With your 700 and 33's, I don't think 4.10's will be an issue.

    I've got 3.42's with 33's in my truck, and like them, but I don't have OD. I bet you rarely used it with your 3.42's.

    Toss up as to whether it will hurt or help economy. In town I doubt you will see much more than +/- 1MPG, but freeway might be different. Just depends where the motor is comfortable, and where you'd end up with 4.10's and OD.

    My setup turned about 2250RPM at 60MPH, and I got 18MPG, so I would imagine anything in that vicinity would net similar results, of course barring every other difference our two trucks have, and our driving style differences.

    From driving my truck with that setup though, compared to my 700/3.08/31" combo, 2250RPM's at 60 really seems to be perfect. Not too much throttle to gain speed if you need to pass, plenty of power left in the same gear to climb hills (could climb mountain passes in 4th at 70MPH) and good economy. 4.10's would be much more enojoyable with the auto in the city though.
     
  4. tecton

    tecton 1/2 ton status

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    i seem to remember doing something like 1700 in the 65mph range

    and in OD i have no power, OD for me is basically a rolling down hill gear
     
  5. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    4.56

    You'll be turning 2145 RPM in OD with the convertor locked at 65mph. That IMO is a good RPM to be at on the freeway. See Dorian's post above.

    John
     
  6. Z3PR

    Z3PR Banned

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    [ QUOTE ]
    4.56

    You'll be turning 2145 RPM in OD with the convertor locked at 65mph. That IMO is a good RPM to be at on the freeway. See Dorian's post above.

    John

    [/ QUOTE ]But what would the RPM's be at 75/80mph ??? I don't know about y'all, but I run my truck out on the big road every now and then with the 75mph speed limit. But ofcorse I'll be running 36's and no overdrive.
     
  7. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    [ QUOTE ]
    [ QUOTE ]
    4.56

    You'll be turning 2145 RPM in OD with the convertor locked at 65mph. That IMO is a good RPM to be at on the freeway. See Dorian's post above.

    John

    [/ QUOTE ]But what would the RPM's be at 75/80mph ??? I don't know about y'all, but I run my truck out on the big road every now and then with the 75mph speed limit. But ofcorse I'll be running 36's and no overdrive.

    [/ QUOTE ]

    At 80 MPH 2640rpm

    At 75 MPH 2475rpm

    Which I still think is fine. My 89 GMC with a TH400 and 30" tires with 3.73's turns 2925rpm at 70mph. And that is from the factory.

    I read a long time ago on here, and in other reliable sources, that a SBC can turn 2800rpm all day long and still live a long healthy life. Now Im not saying its good for gas mileage, but I still get 14ish on the highway with the GMC, (vortec crate 330HP)


    Also to Patrick (tecton), at the risk of sounding like an ass, you do know that you have to change the gearsets from and rear to be able to use 4wd? Mismatching is bad. /forums/images/graemlins/waytogo.gif Some people forget that sometimes, I was mearly trying to help.
    John
     
  8. tecton

    tecton 1/2 ton status

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    yeah i know

    im thinking that since its so hard to get any power in OD i would want a lower gear (no way im getting smaller tires)

    probably try 4.10's to be safe...cause i do drive highway alot
     
  9. 1989blazer

    1989blazer Registered Member

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    My truck's got 33's, a th700r4, and new 4.10's. Seems like a good combo. I still take it out of OD around town, though. I think my tranny needs work.
     
  10. tecton

    tecton 1/2 ton status

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    tranny is fresh rebuilt

    it went south last sept, lol
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    [ QUOTE ]
    But what would the RPM's be at 75/80mph ???

    [/ QUOTE ]

    Thats where driving style comes into play. No 75MPH roads around here, so no chance of ME going that fast in normal driving, so 60MPH is the typical cruise speed for me in this area. The slower you go, the better your economy is going to be, generally. So if you are worried about economy, drive slow. /forums/images/graemlins/smile.gif
     
  12. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    I still say 4.56 /forums/images/graemlins/smile.gif

    John
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    I'd have to agree. If 4.56 puts you in the 2150 range at 60, I say go for it.

    Better acceleration, and better crawl ratio, while still not turning too high or two low RPM's at cruise.

    With an engine putting out a lot of torque at low RPM's (such as a big block) then you can get away with turning lower RPM's, but with a 305 or 350, the lower the RPM's at cruise, the further into the pedal you have to be, which on a 700 means downshifting.

    Side note, wonder if GM/EPA tested economy on the trucks on a dyno/rollers? The 305/700R4/3.08 combo (for instance) was just worthless, especially in an era of 55MPH speed limits! If you can't even use OD, what was the point of installing it? Maybe without wind drag in the formula the OD/numerically low gearsets were worthwhile.
     
  14. tecton

    tecton 1/2 ton status

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    thats the way it is here

    uphill i can barely get over 40mph (in 2nd i can hit 45, but thats at 3200rpm)
     
  15. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    They must not have roller dyno'ed.

    My 88 with a 350tbi, 700R4, and 30.5 inch tires came with 2.73 gears. How in the world they expected to use OD and have it work is beyond me. Without wind resistance, maybe? /forums/images/graemlins/dunno.gif

    John
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    That's my point...without wind resistance, the combos the trucks came with probably work ok...IE at 55MPH, you can probably have a 3.42 truck (or whatever) with stock tires in OD, without a problem.

    You just have to look at NASCAR to see how much HP those cars need to run at 200MPH, where our trucks can get to 100MPH (some of them lol) with 185-200HP. You don't just double HP to go twice as fast. /forums/images/graemlins/smile.gif Wind resistance is a HUGE factor, and not having that factored/present in economy testing is the only reason I can think of that GM came up with the combo's they did.

    Guess I need to do some research, see what I can find on EPA mileage testing requirements. /forums/images/graemlins/smile.gif
     
  17. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    Why don't you take a pic of the internal damage. I will do the same to mine. Sounds like when I broke mine. Could of lost a c-clip, as the crosshaft bolt sheared off, only the fact taht it was stuck in there bent did it not fall out! /forums/images/graemlins/thumb.gif
     
  18. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    I completely agree with you on this one. Finding that info would be a cool find. /forums/images/graemlins/waytogo.gif

    Which somewhat goes to show this; That you cannot buy a new Chevy truck with anything numerically lower than a 3.42 gearset. ( so I have seen )Someone at GM must have seen the light. /forums/images/graemlins/doah.gif

    John
     
  19. tecton

    tecton 1/2 ton status

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    if i can get a ride to the garage ill get some pics when they look at it

    how much $ ya think for a set of 4.10's and a posi rear?
     
  20. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    [ QUOTE ]

    With an engine putting out a lot of torque at low RPM's (such as a big block) then you can get away with turning lower RPM's, but with a 305 or 350, the lower the RPM's at cruise, the further into the pedal you have to be, which on a 700 means downshifting.


    [/ QUOTE ]
    Thats kind of the boat I'm in. I have enough low end torque to cruise at about 1600 to 1800 RPM's with 4.10's and 35's and I get decent mileage on the highway but it drops way off in town. I think 4.56 to 4.88 range would be perfect for me and I bet that 4.10's to 4.56 would be about right for 33's and a stock motor.
    I agree with zz502, I would be looking to go with a 4.56 probably.
     

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