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4wd- Gear mismatch?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Pookster, Mar 5, 2001.

  1. Pookster

    Pookster 1/2 ton status

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    I have a question for you guys; I am uncertain why this is happening to my truck, but since I bought it... when I try to drive it in 4wd, the front wheel seems to lockup on every revolution or so..which leads me to believe its gear mismatch. I havent acutally jacked up the car to count the revolutions... but, it only skips by about 1 inch. I know that the tire which skips the most is the right front side... could it simply be that tire wear is the issue? The right front tire has about 60-75% more tread wear (oldest tire on the truck). The two rear ones are virtually brand new. Coudl this cause it?
     
  2. californiak5

    californiak5 1/2 ton status

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    I highly doubt that the tire wear is doing that. I would NOT put your truck in four wheel drive untill you verify that the gearing in the front end and the rear end are in fact the same. If they are not the same you are taking a very big risk at possibly screwing something up bad everytime it is four wheel drive. Just my $.02

    See Ya,
    Keith

    [​IMG] Born to Drive My K5 [​IMG]
     
  3. Mine does the same thing! I really need to get under there and look, how do I tell if they are different?

    '84 K5

    Chevy in my blood.
     
  4. ftn96

    ftn96 1/2 ton status

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    Well, you need to get into the diffs to check the number of teeth to absolutly verify what gears you have. You need to get in ther anyway. As most people unlike most of us addicts, when they buy a 4 wheel drive or 2 wheel drive for that matter, seem to forget that there is fluid in those "things" under the rear end adn it needs to be changed every so often. Chances are you need to change your fluid as well, unless you have already done so. Not to mention its good to inspect you diffs every once in a while to see how things are holding up.

    Get in there, count the teeth on the pinion and the teeth on the ring gear. Verify that they are the same. If so make sure they are all good without chuncks of metal every where then replace the gasket adn refill the diff with some good 80w90 gear lube. NOTE: You will notice some very small pieces of metal. I mean very very small. This is normal for high miles. But make sure you look at those spider gears. They will most likely look pretty ruff. Then you can consider replacing them or just get some brake cleaner and flush the inside out real good. And refill it and wait till they break.



    Will work for beer, parts and tools.
    90 Jimmy 350TBI-700R4-241-33" BFGs-10 bolts w/4.10's
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  5. Pookster

    Pookster 1/2 ton status

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    Yeah, Problem is, I was new to 4wd when I bought the truck. I know the rear end was replaced before, they must have used the wrong gear set. I did change the fluids in the rear to Mobil 1, and added a bottle of friction additive.

    The gears looked fine, no chunks. of cours,e I didnt bother to acutally count the gears, cause I didnt realize there was a problem. Any ideas on how much this will cost?
     
  6. ftn96

    ftn96 1/2 ton status

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    To have them re-geared? Bout 250-350 in labor and 250 in parts. Now the question is, which one to rebuild? Find out what gears are in the front and then in the back. Then figure out what size tires you plan on running and go from there. But if the back has already been done, I'd do the front to match. Friction juice??? You got Limited Slip I take it?

    Will work for beer, parts and tools.
    90 Jimmy 350TBI-700R4-241-33" BFGs-10 bolts w/4.10's
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  7. Pookster

    Pookster 1/2 ton status

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    Yeah, I figured that was the route. Its a Posi rear (I thought it came standard on all the 87' K5's) and 3.73 gears. It seems they must have replaced the rear with something with a lower numerical ratio because it seems that the front cant spin as fast as the rear.
     

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