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10-Bolt &Transfer Case Lube

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BlazerGuy, Apr 28, 2000.

  1. BlazerGuy

    BlazerGuy 3/4 ton status

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    I am going to replace my to gear oil in my axle and T-case. What kind and how much gear lube do I put in the 10-Bolt? Also I heard that your suppose to put Dexron III in the T-case, but wouldn't gear lube be better? I have a 84 K-5, th350,NP208. thanks for any suggestions.

    Money-->Blazer
     
  2. jarheadk5

    jarheadk5 1/2 ton status

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    If you do have an NP208, ATF (Dexron III) is the correct lube. As far as the axle goes, 80-90w gear oil is the stuff to use. Of course, now that I've said that, someone will post a reason why we should use 85-140w. But that's the beauty of this site; everyone will learn something!

    [​IMG] Semper Maintenance!
    [​IMG] So many ideas, so little money...
     
  3. NYC K5

    NYC K5 1/2 ton status

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    i like the 80-90w oil for my rear. open the plug on the side and fill the diff until it starts to come out.
     
  4. blazer72

    blazer72 1/2 ton status

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    GM went to ATF in later years for better milage, I run Castrol 75w90 GL4 in every thing the NV4500, 203 ratio box and the 205, The Dana 44 in front has cheap 80W90 in it as it has a bad seal! Since the castrol is $18.00 a bottel from GM and 22.00 from Dodge!!! The Late model 205 from like 80 up have ATF in them. In talking to deffrent Trany shops if you work the truck hard use 80W90 in the t-case, ATF if it used lite. GM and ford also used the same oil in the t-case as was in the trany so if it had 80W90 in the trany in had the same in the t-case.
     
  5. Oil Man

    Oil Man Registered Member

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    Blazer Guy,
    Your NP 208 calls for a Dextron III transmission fluid. The EPA in recent years has made the Auto MFG's get better mileage and thats one way they can get better mileage is to use a thin oil in the T-case. Yes you could use the 80w-90 in the T-case but you will suffer mileage drop. If you want more protection for the T-case then my recommendation would be to use the Lubrication Engineers brand Allison transmission fluid #7500. It far surpasses the Dextron fluid will not hurt your mileage and was made for the BIG trucks fore severe duty service. This fluid will greadtly reduce wear and go longer oil drains. As a result of using the LE 7500 for your T-case you should see smother quiet operation than your used to in the past.

    As for the gear oil for your rear end, I also recommend the LE 607 SAE 90 gear oil. Being a straight 90 wt there is no viscosity modifiers to break down so the oil stays a constant viscosity and protects better. When compared to a synthetic gear oil the LE showed about 33 times less wear. The LE had 12% more EP (extreme pressure) additives plus an extra EP additive that withstands 400,000 lbs that no other oil company uses. It protects better than 85w-140 and flows better at cold temps also. When comparing the 80w-90 to the LE SAE 90 and an 85w-140 the LE SAE 90 is about 25% thicker. However the 85w-140 is about 300% thicker, yet the LE SAE 90 protects better. This means that as you are getting better mileage you are protecting the rear end gears and bearings better also.

    These products can be purchased from a company called Mag-Hytec at 1-818-786-8325 or at their web sight at www.mag-hytec.com

    Sincerely, Kevin
     
  6. Mr Red

    Mr Red 1/2 ton status

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    Does the LE 607 SAE 90 gear oil work on limited slip and posi gears? I'm getting ready to change mine & what you say makes sense and I'm willing to trust opinions of fellow K5'rs.

    <font color=red>David, '86 K5</font color=red>
     
  7. BlazerGuy

    BlazerGuy 3/4 ton status

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    I went to take the fill plug off but the previous owner(i guess) severely rounded it off. It looks like a circle. Now What!?

    Money--&gt;Blazer
     
  8. Blazer79

    Blazer79 1/2 ton status

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    You can weld a new bolt on top of the rounded plug. You'll be able to use it that way or just once for removing it and get a new one.

    <font color=black>//////
    What the heck!...Drive it like gas is $0.50/gal!!!
    </font color=black>[​IMG]
     
  9. BB454

    BB454 1/2 ton status

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    Thanks for your detailed advice Kevin. I also use 80w-90 in my NP208 and I have been wondering what the pro's & con's was (except for not trusting the rear oil seal on my SM465) If mileage is the only concern then I would stay with the 80w-90. Thanks.

    BB454
    IF IT DOES NOT HAVE 8 PISTONS - IT'S BROKEN !
     
  10. Oil Man

    Oil Man Registered Member

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    Mr. Red,
    Yes the 607 will work with posi. But if the rear end takes posi additive then I would add it like the MFG says too.
    Kevin
     
  11. 6.2Blazer

    6.2Blazer 1/2 ton status

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    The 10-bolts take about 2 1/2 quarts of 90 weight or equivalent. I like the synthetics myself.
    For the NP208 transfer case, I would use ATF (Dexron II or III). I would not recommend running anything else because the 208 is specifically designed to run ATF, in terms of tolerances and lubricating efficiency, and running something like 90 weight in it will hurt it more than it would help it.
     

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