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What should I do (rear rebuild question)

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by bigcat44, Feb 21, 2005.

  1. bigcat44

    bigcat44 Registered Member

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    My 89 Jimmy is needing a rear diff rebuild and would like some suggestions as to what I should do. I currently have all stock 350 engine, 10blt frt and rear stock gearing, np241 transfer, 6" lift and 33" tires (soon to be 35). My rig is preety much used as a daily driver and would be used for the occasional weekend light mud/dirt off road excursions. This will not be used to rock climb :D . What should I do??? Thanks in advance for any and all suggestions.
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    With 35's on the horizon you might want to upgrade the diff's a little, and it'll likely be about the same money as rebuilding a fairly weak rear 10 bolt. A semi-floating 14 bolt rear will be a lot stronger with not much loss in ground clearance. I'd personally look for a matched set of 3/4 ton diffs and swap them in...the majority have 4.10's which should be better than any factory 10 bolt gearing as well.

    Rene
     
  3. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    You would definitely like the lower gearing, especially if you have overdrive. And especially if you go up to 35s. I swapped in axles for lower gears and I wish I would have done it sooner.

    So I would second what Rene said. Look for a different set of axles to get lower gearing.

    If you stick with the 10bolts and you want some security against breakage, look at installing some Superior Gear alloy axle shafts. Offroad Design has them for $101 per side.
     
    Last edited: Feb 21, 2005
  4. Jonny-K5

    Jonny-K5 1/2 ton status

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    with 33-35" tires and a 700, i personally like 4.56 gears. i've got 4.56 w/ 33's and its perfect, with 35's it would be adequate. with 4.10's/35's your gonna have to be going pretty fast to need the OD. 4.10s will be better than what you got now, but not ideal.

    a good find would be the 6 lug 14b semi floater. pretty hard to find but a good uprgade and will be you keep your current rims. if you go 8 lug, you might as well get a full floating axle. i think they are easier to find, much stronger,parts are cheaper,and you'll never have to worry about it for the type of wheeling you do. another plus is that the military used them with 4.56 gears and a detroit locker. this would be ideal, then just regear the front and do an 8 lug conversion.

    alot depends on how much your willing to spend.

    cheapest would probly find a pair of 3/4 ton axles with 4.10's, buy 8 lug rims and your done. but like i said, 4.10 is not ideal.

    second cheapest would likely be finding a 14b military rear, regearing front +rims.

    what will eat up the most cash is if you have to buy an axle, then rebuild/regear it, on top of doing the front + rims.

    whatever you decide make sure you think it over completly. it would be a shame to have to do it all over again causs the axle broke, gears arent deep enough,or you want to go bigger tires.


    .02
     
  5. Jonny-K5

    Jonny-K5 1/2 ton status

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    good point. i have alloy shafts in my 10b, and i feel this setup will hold up to 35's with mild wheeling. the only down side is the cost of regearing. i'd be money you've got a gov-lock in that rear as well, in that case you'd need a new carrier. plus regearing the front, it gets pretty expensive and you still have 10b's. if you get the bug for bigger tires like most of us do, your axles simply wont be strong enough.
     
  6. bigcat44

    bigcat44 Registered Member

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    Yeah right now I am looking for the cheapest method. I just replaced both rear axles and seals and looking for something with long term benefit (So I don't have to fix them again!!). Thanks for all the replys and info. I'll start looking for some 14sf around here and San Antonio (moving there in June). Yes I have the TH700R4 w/od, sorry I didn't put that in the post.
     
  7. bigcat44

    bigcat44 Registered Member

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    Quick question, what is my current stock gear ratio right now? is it 3.73?
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    What are the codes starting with "G" in the glove box? G80 will be the gov-lock, another G code should be ratio.
     
  9. bigcat44

    bigcat44 Registered Member

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    Just looked at the codes on the service part sticker in the Glove box. There is no G80 code, there is only one "G" code that is GT4 does this say anything?
     
  10. bigcat44

    bigcat44 Registered Member

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    OK I found a good page with all the RPO codes here: http://www.chuckschevytruckpages.com/rpo_codes_1973-87.html

    so what this tells me is that I have a 3.73 rear but no Gov lock? Is this a good thing or a bad thing? I am planning on doing the rebuild and a locker for now staying with the stock gearing for now. I will do the axle swap down the road but for now I just need something to use it as a daily work truck.
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    Yes no gov-lock, that is a good thing.
     
  12. MarcS

    MarcS 1/2 ton status

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    If your only going to do light wheeling and not go bigger than 35"s, I would just regear the axles you have. An install kit is pretty cheap and has all the new bearings and seals. The axle will be good to go. You could then upgrade it as you can afford it with shafts/posi/locker etc... If you get another axle, there is no guarentee what condition its in and you may have to refresh it on top of buying the axle.

    I have a 700/208/35" with 4:11s. Its OK. But next time I would go with 4:88s with the 700r4.

    Just my .02 Good luck.
     
  13. bigcat44

    bigcat44 Registered Member

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    Great, thanks for all the help. Marc, that is what I was thinking. I found a few different axles at local salvage yards but outside of tearing into them and seeing for myself, I could just be buying something I would have to rebuild. I am going through Desert Rat as they have a local shop and have been great to deal with. Though I may consider going with the 4.11 frt and rear depending on costs with the current stock 10blts I have now. I'll call them tomorrow for a price quote.
     
  14. MarcS

    MarcS 1/2 ton status

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    With my 4:11s Im turning about 1600 RPM in OD (WAY to low 4 me) at 60 MPH and in 3rd about 2300 RPM. Thats why Ill go lower gearing next time around.
    I would prefer to be around 2300 around 65/70 MPH.
    I leave it in 3rd around town and the performance isnt that bad. If my engine was fresher Im sure it would be even better.
     
  15. Jonny-K5

    Jonny-K5 1/2 ton status

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    if your going to regear both axles, go with 4.56. trust me, 4.10 isnt enough. i would go with a trutrac limited slip. its stronger than your stock diff, provides better traction, and wont break parts as easy as a full locker would. as long as your not climbing rocks the TT would be a great choice. i had one in the back of my truck before i swapped gears. i really liked it for mild wheeling.
     
  16. Nicks 72

    Nicks 72 Registered Member

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    I dont have a lot of expierience on the weaknesses of a 10 bolt for wheelin(other then the obvious smaller size of the unit compared to a 14 bolt) I did break two out in the Pismo dunes jumpin but that was a given. I do have a lot of expierience in what goes out on street trucks with bigger tires and/or a lot of miles and 9 out of ten its that damn GOV LOCK. In my opinion they are a time bomb ready to blow. I have replaced so many of these in every aplication they come in from old to silverados. Your better off having an open in my opinion then a GOV-LOCK.
     

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