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axles and ring and pinions

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by rphenry250, Sep 11, 2002.

  1. rphenry250

    rphenry250 Registered Member

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    hey ive gotta 83 k5, with a sm465 tranny and a np205 tcase. its got 10bolts on it with 2.82 gears in it. i want to run like 3.73 gears or 3.90 gears. should i go ahead with this axle or go hunt down some 12bolts?
     
  2. heavy4x4

    heavy4x4 1/2 ton status

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    Personally, I'd go find a 3/4 ton donor truck and take the front and rear axles. Depending on what truck you choose, you'll end up with the proper size 14 bolt ff rear, and a 3/4 ton 10 bolt or Dana 44. Both will be 8 lug, so new wheels will be necessary. But, all of the before mentioned items could be found for less than $500 - if you do some shopping around. Also, you may luck out and get the 3.73 ratio you want.
    You might want to crunch some numbers on 4lo.com's calculators to find a good rearend ratio because they wouldn't put 2.82's (if that's really what it has) in a truck if that weren't ideal (for gas mileage, proper cruising rpm/power)
     
  3. rphenry250

    rphenry250 Registered Member

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    the axle has 2.82's in it b/c the truck originally was a 700r4/np208 combo as stock, then it was a th350/np203 combo when i bought it, now it is a SM465/np205. i did the auto to manual swap myself.
     
  4. rphenry250

    rphenry250 Registered Member

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    oh yeah i got another question im runnin about 1800 RPM @ 60mph right now,,, if i was running 2500 rpm @ 60, which would get better gas mileage?
     
  5. heavy4x4

    heavy4x4 1/2 ton status

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    It kind of depends. More fuel will be dumping in at higher rpms to keep the engine spinning that fast, but if the engine bogs down and is struggling to push you along at 1800rpms your gas mileage will suffer too. Typically a good number to shoot for is 2200-2300 rpm at 65mph.
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    Not to be anal, but you've got 2.73's if someone didn't put something else in there. (and I've never heard of 2.82 aftermarket gears) http://www.slosh.com/cars/brochures/

    If you don't have intentions of running bigger tires of off roading a lot, just find a set of ten bolts or D44/12 bolt. 3.73's for me are WAY too much with 31's and no OD for freeway speeds, I'd go no higher than 3.42, and maybe even 3.08 for your setup. (both very common)

    3.23 would probably be ideal for your truck as it is now, but you couldn't get those in a 10 bolt, or AFAIK, 12 bolts either.

    Either way, no matter what gears you are thinking of, if you plan on making tire sizechanges later on, don't waste time/money on a numerically low set of axles now.
     
  7. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    </font><blockquote><font class="small">In reply to:</font><hr />
    3.23 would probably be ideal for your truck as it is now, but you couldn't get those in a 10 bolt, or AFAIK, 12 bolts either

    [/ QUOTE ]

    Dorian is correct about the 12 bolts AFAIK, but you can get them for 10 bolts (try www.drivetraindirect.com/html2/dtdframehome3.html )

    Click on Ring and Pinions (applications)

    3.23 Richmond 49-0019-1


    I actually have a set I was going to sell to Dorian if I can find them. They matched the 3.23's that were in my 14FF from the factory (still have pics with part numbers) 1980 K20.

    I will say this though, they are few and far between stock in fullsize rigs (not sure about cars). One other guy says he had them in a rig, but mine are the only one's I've actually seen with my own eyes.
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    I meant you couldn't get them stock....but I guess you are right, 1980 was a 10 bolt front eh?

    I wonder what the truck dealer brochures show for axle ratio options? The Blazer/Suburban ones that are online show basically only 4 different ratios, 3.42 IIRC only being available in Suburbans.

    Wonder how many different ratios say an '83 K20 could have come with...probably about 6?
     
  9. MNorby

    MNorby 3/4 ton status Premium Member GMOTM Winner

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    my truck came stck with 3.23 gears. It was originally an '86 we think.
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    yeah, wonder if anyone has a dealer brochure for the trucks? I'm curious as to how many they had...K5's weren't so lucky I'm sure : )
     
  11. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    </font><blockquote><font class="small">In reply to:</font><hr />
    1980 was a 10 bolt front eh?

    [/ QUOTE ]

    Yes it was a 10 bolt front (K20).

    I don't know if the dealer has that info or not in their sales brochure (or in any brochure for that matter) after all this time. Somebody MAY have it as it was a factory option (although it doesn't seem to be a popular one). I have even been told by "GM experts" that my truck could not have come with 3.23's especially in a 14FF. They just about $hit when I showed them the ring and pinion with the GM stampings on it, and the R&amp;P was easily identified as being from a 14FF. I have had to eat crow for some of the things I have said, it was nice to have others eat it for a change /forums/images/icons/tongue.gif /forums/images/icons/grin.gif
     

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