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Ratio?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Sammy, Jan 8, 2001.

  1. Sammy

    Sammy 1/2 ton status

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    How do I find out what kind of an axle I got. (Dana60 Danna44 .....???) And what about the ratio, can it be checked without taking it appart. I'm about to swap the 31" tires for 35" ones, and I want to know if I need to regear them. About regearing. what is advised for 35" tires.



    "K5 Grand GT in the Netherlands."
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Hey Sammy, first off have you checked the tech section on this site? There is a good visual aid for axle identification. Your profile doesn't say what year your K5 is but pretty common axles for 78 and newer were the 10 bolts front and rear. For the rear there were only 2 possible diffs, the 10 bolt and the 12 bolt. Count the bolts on the cover, thats what'll tell what you have. For the front again there were 2 diffs, the 10 bolt front and the Dana 44. Both have 10 bolts holding the cover but the 10 bolt has a much rounder cover.
    There are glove box codes for axle ratio's, but the best way to verify you ratio is to pull the cover off. Either count the teeth or look for a stamping on the edge of the ring gear. Mine for example has the numbers 41/11 stamped on it. Divide the numbers and you get the ratio, in my case 3.73:1. This method also gives you the oppotunity to inspect the diff and clean and replace the fluid, something often neglected by most people.
    Common ratio's that work with 35" tires are 4.11's or 4.56's. A lot depends on what kind of wheeling you do, transmission type, and what kind of driving you do. I use 3.73's to turn my 35's but I have a 4 speed standard with a very low first gear. My trucks spins at 2400 RPM cruising on the highway and this set-up works for me. I am on the edge of needing a gear change though and I might be doing this if I increase my tire size (37's maybe)

    Rene

    [​IMG]
     
  3. Sammy

    Sammy 1/2 ton status

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    It is a 1988 Grand GT K5. The rear diff has new satalites put in about 8 months ago and I only heard that it was an autolocking version. (Spare Diff). I'm a bit scared that it might be something like 3.07.

    "K5 Grand GT in the Netherlands."
     
  4. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Well an 88 would almost certainly have 10 bolts. If you have overdrive you probably have something numerically lower than 3.07's. 3.42's and 3.73's are also common.
    Stiil the best way to find out is pull the cover off, it'll satisfy your curiousity and get some maintenance done at the same time. "sattelites"? Do you mean "spider gears"? Autolocking? Are you talking about a front diff? Or a rear? I suspect you mean it has a "gov-lock", but I'm guessing. They are pretty common, especially in the newer K-5's.

    Rene
    Check the post "Dana 44 questions" I just posted some pics from the tech section there.



    [​IMG]
     
  5. Sammy

    Sammy 1/2 ton status

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    I'm talking about the rear axle. Never even looked at the front one, I only have my Blazer for a year now.

    They called it sattelites. They are the 4 little gears that do the actual differential work. They are new in mine. The locking system is as follows. A small flywheel rotates if the axles rotate in different rpm's. It opens up if it rotates faster and then pushes a brake into one of the gears. The diff then locks up. The actual locking is done by a set of plates. I'm not sure if I have stock axles, but if I have 3.07's, will that be a problem when off-roading with 35"? I have a 4 speed automatic Tranny.

    If any of this is not clear, I have a good excuse. I live in the Netherlands. lol.



    "K5 Grand GT in the Netherlands."
     
  6. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Yeah, those are the spider gears. Also you have a Gov-lock.

    3.07's and 35's with 10 bolts and a 4speed overdrive auto is a recipe for broken parts [​IMG]
    The 700R4 transmission you have will burn up if you have 3.07's and choose to go with 35's and no gear change. I would recommend 4.56's if you want 35's. The rear 10 bolt may not live with 35's either, it depends on how it is driven and wheeled. If it sees mostly pavement you may be alright.

    Rene

    [​IMG]
     
  7. Sammy

    Sammy 1/2 ton status

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    what about a 10-bolt with 4.56 ratio or a 12-bolt with 4.56 ratio. I heard a 14-bolt has to have 8 hole rims. I have 2 sets of 6 hole rims.



    "K5 Grand GT in the Netherlands."
     
  8. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    If you want 35's and have access to a 12 bolt I would use it, it is a little stronger than the 10 bolt, the 10 bolt front would probably be OK as well, as long as you get the gears needed to turn the 35's. Your tranny will thank you.

    Rene

    [​IMG]
     
  9. shaggyk5

    shaggyk5 1/2 ton status

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    remember, you need the same ratio front and rear as well.

    --matt
    shaggyk5: 85 Blazer, 6" lift coming soon!

    aint nuthin in the world like a heavy chevy!!
     
  10. Sammy

    Sammy 1/2 ton status

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    Ok I checked last night and I seem to have a 10-bolt in the back and 10-bolt or a dana44 in the front. I'm planning to mount 35x14x15 Thornbirds I already have. If I re-gear both to something closing in to 5:1. Wil it last? (I'm no rock crawler you know, just woods, beach, hills.)

    "K5 Grand GT in the Netherlands."
     
  11. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I'd go with the 4.56's, and maybe upgrade to stronger axle shafts.

    Rene

    [​IMG]
     
  12. Sammy

    Sammy 1/2 ton status

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    just the shafts? Is that all? :)

    "K5 Grand GT in the Netherlands."
     
  13. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    The lower gears will apply more torque to the axle shafts, so a stronger shaft may be needed. You might also consider the fusible hub things (thats the technical term there [​IMG]) that warn makes, they are designed to fail before your front axle u-joints let go. I think they are about $12 and are easy to change. I would also lose the gov-lock in favor of just about anything else (just my personal opinion)
    Also look into getting the biggest tranny cooler you can find, turning those 35's is bound to generate some extra heat, which will drastically shorten a 700R-4's life.
    Manual hubs up front would also be a good idea. Not too expensive but definitely stronger than auto hubs.

    Rene

    [​IMG]
     
  14. Sammy

    Sammy 1/2 ton status

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    What damage can the gov-lock do? Lock up and break the axle? Btw. I don't know if I have one too in the front.



    "K5 Grand GT in the Netherlands."
     
  15. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Your front is open unless someone else added a traction aiding device before you bought the truck.
    Some people swear by Gov-locks, some people swear at them. I fall into the latter category. I haven't had one that worked well yet. They are not the strongest or most reliable unit around. Their best feature is that they behave like an open diff for the most part, their worst feature is that they also seem to behave like an open diff off-road as well [​IMG]

    Rene

    [​IMG]
     
  16. azjimmy

    azjimmy Registered Member

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    I agree with tRusty on the 4.56's, but I would'nt rule out 4.88's. I currently have 4.88's w/35's on my '76, I'm running a TH350 and it's a little buzzy on the freeway, but I'm sure if I had a 700R4 it would be perfect! Just a thought. Pat

    <font color=red>Don't sweat the small stuff, and it's all small stuff!</font color=red>[​IMG]
    '76 Jimmy, 6" w/35's 4.88's and all locked up
     
  17. TX Mudder

    TX Mudder 1/2 ton status

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    Well, I broke a 12bolt rear withh 33's, so I would guess the 12 bolt is only marginally stronger, maybe 15%?
    -- Mike
     
  18. bablazer73

    bablazer73 1/2 ton status

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    the 12 bolt is only slightly stronger that the 10 bolt. The pinion bearing is a little bigger and the ring gear is a little bigger. the drawback was getting parts. "In my opinion" a 10 bolt can be made as strong or stronger than a 12 bolt. There are alot more parts available for these axels. the same center section was used in the camaro/firebirds of the 70's. I used one in a 11 second nitrous feed Z28. Very violant off the line. never broke the axel. I like the 10 bolts. any part is still available, and many upgrade parts are also.but, "in my opinion" . I would consider a quality posi/locker unit and upgraded axels on either axel choice. a full floater kit would be a great investment. I am not a big fan of c-clip axels. I have broken 12 bolts and all my trucks have 14 bolts.

    your right. I don't understand the jeep thing!
     
  19. Sammy

    Sammy 1/2 ton status

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    I live in the Netherlands. 14-bolters are all 8lugs here. I have about 12 6lug rims. Would be a waste. I might go for the upgrades I think. Parts are hard to get here. Importing some axles would go well. But not a whole 14-bolter. Thanks for your help guys! Before I found this site I was considering selling my Grand GT because nobody knew anything about it. Now I know where to come with qeustions.



    "K5 Grand GT in the Netherlands."
     

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