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K5 rear driveshaft problem

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by jdemaris, Apr 10, 2001.

  1. jdemaris

    jdemaris Registered Member

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    I have two diesel K5s, an '83 and an '86 - not that the diesel makes any difference with
    this problem. I burn up rear u-joints all the time. My’87 Suburban, with the same joint,
    gets over 100K on the rear -joint (longer wheelbase - less angle). I've tried the usual
    attempts to remedy including various u-joint brands and grease, lowering the transfer
    case to make the angle less severe, bleeding the newly installed u-joint of air when first
    greasing, etc. etc. Lowering the transfer case by relocating the factory bushings required
    lowers the [censored]-linkage bracket. It didn't make the joint last any longer, though. I also
    had one bad episode with NAPA. They had some u-joint retainer straps that were a few
    thousandths too big. My driveshaft flew off and blew my transfer case to pieces. The
    most alarming thing to me is these joints go with little warning, i.e. they don't start
    making noise gradually or vibrate. I had one occasion where I just came home from a
    200 mile trip at 75 m.p.h. speeds - all very smooth. Parked in my driveway for minute,
    then tried to back out - and my driveshaft fell right off. The joint goes bad, wobbles a
    bid, gets loose in the straps, and the caps fall off. Seem, if it could be converted to a
    u-bolt retaining system, with a drive-flange with ears (that prevent cap fly-way) things
    would be much better. Some K5 Blazers with standard shift have this setup. Has anyone
    tried changing the angle of the rear-axle, i.e bringing the drive-flange up and thus
    reducing the driveline angle? It appears this would do more than lowering the transfer
    case. I have an '86 S10 Blazer and I've gotten over 100K from the rear u-joint - and the
    angles are very slight.
     
  2. Wheels

    Wheels 1/2 ton status

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    Get with Jesse (drivelineman) he's the guru on driveline angles. Use an angle finder to determine if the rear pinion yoke and the t-case output shaft are operating at the same angles from 90 degrees.
     
  3. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    You might need to shim the diff a bit to get the angles a little better. You didn't mention if the truck was lifted or not, obviously the more lift the worse life gets for the u-joints. Although I wouldn't ever expect 100K out of a u-joint in a K5. Mine has the 4 speed manual, and I usually get a slight vibration that steadily gets worse when a u-joint is going. The last U-joint that went on my truck did so just North of San Francisco. We were coming home from Disneyland and towing a 5500 lb trailer. I felt the vibration but had no clue what it was, so we continued driving and just took it easy all the way up the coast. Arrived home no problem and finally took the time to try and find this vibration. There wasn't too much left of the U-joint by then but we had driven almost 1000 miles since the vibration started...[​IMG]
    I seem to get about 2-3 years out of my rear u-joints.

    Rene

    [​IMG]<A target="_blank" HREF=http://jules.coloradok5.com>http://jules.coloradok5.com</A>
     
  4. jdemaris

    jdemaris Registered Member

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    I am not sure of your set-up but most K5s with standard shift use a different universal joint with outside lock rings instead of the inside clips used with automatics. The former setup would not be prone to the cap-fly off problem. Both of my k5s are standard height.
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    I'm gonna go out on a limb and say that the u-joints/yoke/attachment methods are all going to be the same on the same year Blazer, no matter transmission, etc. Later on, GM went to straps, as opposed to U-bolts. I'm sure it was cheaper/easier to make that way.

    Have you inspected the yoke for wear? I had a bad yoke without knowing it, replaced the u-joint, and 3 miles down the road got the vibration back, right around 35mph. Finally looked very closely, and noticed that some PO had installed the C-clip's on the u-joint UNDER the strap at one point, and with the resulting wear of the u-joint, it managed to ruin the yoke. With a new yoke, and care of how the u-joint was reinstalled (c-clip inside the strap, and the "C" part of the clip up against the yoke, not the inside edge of the strap, I never had a problem again.

    My friend also was chewing up u-joints, and it was because when he installed lift blocks, the pin on the spring had dropped into the hollow cavity of the block, not the center hole, and the rear axle was out of alignment.

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  6. jdemaris

    jdemaris Registered Member

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    Thanks for the reply, but I don't agree about the u-jonts being the same. I've worked on several 1/2 Suburbans and K5 Blazers - and most if not all with a standard trans. used a u-joint with outside lock-rings (NAPA #371 or 377) whereas the same types of vehicles with automatics have the u-jonts with the inside snap-rings (NAPA #534G or 235). I've seen this on vehicles from 1982 to 1997. As far as yoke wear goes, mine are fine. I've got two K5s, both automatic, one 1983 diesel with a TH400 and the other a 1986 diesel with 700R4. They both have had the u-joint problem ever since I've owned them (over 10 years). I am curious if they had the problem when new. My 87 diesel Suburban with T400 trans. had 125K before the first rear u-joint went. The immediate cause when the joint fails is no lubrication - I always find it dry when it goes. This makes me think that the seals in the replacement joints don't hold up to the excess movement due to the excessive angle. I got to a point that I would grease them every month, but they still go. One thing I have not tried is getting an O.E.M. joint that is not greasable. Maybe it has better seals? In contrast, I just put a u-joint in the rear driveshaft of my 1987 Subaru wagon - the first lasted 187K miles and it wasn't greasable. I'd be happy to get 50K with the Blazer. I've been thinking of welding straps across the outside of the pinion yoke that would prevent the u-joint caps from flying off when the joint goes bad - this would save my transfer-case from blowing apart (hopefully). Seems silly, to carry an extra driveshaft around all the time, but I do.
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    All you have to do is call the dealer and see how many different styles of "yokes" they list for your respective year of K5. I'm seriously betting there is one. I can't guarantee it, I don't have my parts book for '85/'86 in front of me, but i bet GM can tell you. There very well may have been "substitute" yokes, depending on where and when the truck was made,which is entirely possible. However, they all used the injection molded plastic to retain them originally if I'm not mistaken, so GM could really have cared less whether inner or outer snap rings..except for servicing the vehicle. RWD cars of the same vintage did. Ued to be that the replacement u-joints would have both styles of clips in the box...the ones I just bought did not..1976 K5, external snap rings.

    The earlier (mines a 70's vintage) yokes had (or some did) a small "bump" to do exactly as you mentioned, keep the caps from coming off. Bolted right up to my 10 bolt..i was told this yoke came off a mid 70's Camaro...having problems geting the seal to seal, hopefully when I replace the seal, the problem goes away. Maybe, like me, if you can't get the problem solved, you are contemplating throwing the whole damn axle away and getting another one!



    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  8. drivelineman

    drivelineman 1/2 ton status

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    i'd make it one ton on the joint your eating up - they hold up well - 530-872-5725
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    Checked the GM parts catalog last night for 1985 and 1986 1/2 ton (8.5") rear axles..all use the same part number yoke. HTH.


    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     

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