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Driveline thuds

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BettyBurb, Dec 14, 2002.

  1. BettyBurb

    BettyBurb Registered Member

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    This morning I took my 1988 Suburban half ton, 4wd with 350 out for a few errands. Went about 5 miles about 50 mph. Had to make a u-turn didnt quite make turn so had to stop go into reverse. At this point I heard a loud thud and jerk in driveline. Went forward and heard and felt rapid thuds seem to come from front. Headed for home thuds went away and cruise home at about 55 mph. Stopped in front of house and stared back up and thuds again. Seems from front end, front end was visibley bouncing. Fairly rapid. Almost sounds like a u-joint.

    Looked at front and rear driveshafts u-joints look good. Noticed that I can turn the front drive shaft by hand nearly a quarter turn with vehicle off and in park. Is quarter turn ok ???

    Other info, replaced rear transfer case seal and driveshaft about 20,000 miles ago - no problems since.

    Also a few days ago took burb on 400 mile round trip. Got bad gas at beginning of trip and about 75 miles into trip started having fuel problems. This was in remote area and speed was reduced to about 35-40 miles an hour for about 75 or 80 miles. Got fuel filter and problem solved. Drove rest of trip with no problems. Could something in driveline such as transmission, transfer case have been damaged ??? I dont see how, but maybe ???

    Any ideas on how to trouble shoot this etc will be appreciated.
     
  2. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    Since your profile is not filled out I will assume your burb is stock. Clunks are normally from u-joins. How did you decide they were good? Also, the straps that hold the joint to the pinion yoke could be streched. A bouncing front sounds like shocks, unrelated unless you were in 4WD. Were you in 4WD?
     
  3. BettyBurb

    BettyBurb Registered Member

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    Yes it is all stock. Not in 4wd. I have had bad u joints on other vehicles and have been able to see that they are bad by trying to turn the shaft. Yes it could be u-joints, but in my experience the u-joints only clunked once or twice on take off , not several times at low speed. This is not really like the clunk of u-joinst that I have experienced, more viloent in nature. The bounce is certainly not shocks. Maybe bounce was poor description, more of a sharp upward jerk. The front end jumped up with each thud, it was rather violent in nature. Sort of a combination of a shudder and a bounce. Or almost like running over a very a square rod about 1" by 1".

    How about the quarter turn of the shaft - is that normal ??

    Also, I can start up and no problem and then stop start no problem. And then the thuds will start up again. Feels like something is going to break.

    Feels like it is coming from the front end driveshaft, axle or wheels.

    How is the best way to determine if it is u-joints ???

    Thanks
     
  4. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    Best way to determine if a u-joint is bad is to remove and inspect. They can also make a squeeking noise if low on grease.
    Front shaft should turn freely in 2WD. From what you decribed you may have front hub hanging up (assuuming auto-hubs) If that is the case replace them w/ a good set of aftermarket manual hubs.
     
  5. reddog64

    reddog64 1/2 ton status

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    did you try turning the back or the front driveline?

    The front should free spin, back should be tight, minus a little play...

    Can you stick your fingers in between the knuckles and turn the front shafts over? /forums/images/graemlins/confused.gif
     
  6. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    She said the front turned a 1/4 turn, that's why I mentoined the hubs.
     
  7. BettyBurb

    BettyBurb Registered Member

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    The rear driveshaft has no play while in Park. The front drive shaft, transfer case in 2-HI will not turn freely - but will turn almost a quarter turn.

    So in 2-HI the front shaft should normally spin freely ??? With auto hubs how do the hubs engage/disengage??? I thought that they were always engaged and that when tranfer case is put into 4-Hi the front shaft simply starts turning. Manual hubs allow the hub to be disengaged when in 2WD, right ???
     
  8. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    I'm with Jim (BigJBear) on this, It sounds like it's in 4wd or the auto hubs are engaged.
    I'm beginning to wonder if the linkages got screwed up when the case was out and that thing is in 4wd. I haven't messed with auto hubs before but I though the front tire need to make one revolution before the hubs would engage. That would take about 3 truns of the front drive shaft before it should stop if I'm right.
    Try this, if you have auto hubs. Get where you can go forward and backwards about 20-30 ft. Put the truck into 4 high and drive forward about 20 ft and stop. Put the case back in 2 high and back up about 20-30 ft. That should make sure the hubs have unlocked. See how much you can turn the drive shaft then.
    See even if the hubs had locked for some reason it should not have done the hopping like it was in 4wd. THe drive shaft would have been free to spin in the case so the front diff should have let it spin without the binding that causes the hoping.
    Your year truck is notorious for busting transfer case mounts. It lets the rear of the drive train move and bounce off the floor and several have had it shift sideways enough to acctually be in 4wd even though the shifter showed it in 2wd. Inspect the case mount. Might take a crow bar and see if you can lift the case by prying up on the bottom of the case off the skid plate and see what happens at the mount. Just be carefull not to put to much pressure on the aluminum housing of the case when your trying to see if the mount is busted.
    Most of us have ZERO respect for those auto hubs. They are unreliable and tear up. Advance Auto parts sells Warn Premiums for a decent price and usually has them in stock. If it were mine I'd loose the auots and replace them with the Warns. Auto Zone carries the Superwench hubs. Not a bad hub for the price either.
     
  9. BettyBurb

    BettyBurb Registered Member

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    Grim Reaper,

    Did as you described "Try this, if you have auto hubs. Get where you can go forward and backwards about 20-30 ft. Put the truck into 4 high and drive forward about 20 ft and stop. Put the case back in 2 high and back up about 20-30 ft. That should make sure the hubs have unlocked. See how much you can turn the drive shaft then."

    In 4Hi front drive shaft will not turn. When back in 2Hi same thing - 3/4 turn. Seems to me that the tranfer case is shifting from 2wd to 4wd ok, but that the problem is in the axle or hubs. What do you think ???

    Drove it aroound in 2wd with no problems for a little while this morning.

    Will check transfer case moount as you said. It has been 20,000 miles since front bearing repack. How often should this be done ???

    Irregardless I will repack bearings and install warn manual hubs.
     
  10. RedBrute

    RedBrute 1/2 ton status

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    I just went out under my '87 blazer, 208 tc with auto hubs. I turned the front drive shaft by hand. at about 1/4 turn I could hear/feel both autohubs clunk softly, at 3/4 turn both hubs clunked and locked so I couldn't turn the shaft. The description of the sound and feel your getting leads me to believe you have a hub going bad. They come out easy, 6 torx screws and one snap ring. Pull them both and inspect them.
     
  11. BettyBurb

    BettyBurb Registered Member

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    Correction - 1/4 turn in 2wd
     
  12. loriandmarke

    loriandmarke Newbie

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    On my first blazer, the guy I bought it from had the bearings done at a local shop, they put one of the autohub components in backwards and it failed. The same thing may have happened to you. I have ended up replacing the autohubs on all 3 of my blazers within a year (they just don't seem to hold up if you use them). I personally like the Warn Standard hubs, they aren't as pretty as the premium hubs, but they only require a quarter turn to engage.
     
  13. BiggerRigger

    BiggerRigger Registered Member

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    are you sure that this is your front end that is makeing this noise as my 89 jimmy was doing just what you are saying and it turns out that it was the rear junk-loc that was on its way out but I too thought at first that it was coming from the front by the way it was making the whole truck jump like I ran over something.....check that rear diff
    Aaron
     
  14. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    I had something like this happen to me... it was my caliper mounting bolts...one was sticking out so far, it was knocking the inside of the rim and getting hung up before one day I heard a "CLANG" and something fall on the ground and my brake pedal went soft. The bolt finally got sheared off by the wheel. Replaced it, haven't had a problem since...weird.
    If it's the hubs, you might hear them while you're driving. If it's not too cold, roll your windows down and drive and see where it's coming from.
     
  15. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    BTW, by what you describe, your auto hubs are working CORRECTLY! The auto hubs work by engaging when the front driveshaft turns when the T-case is put into 4wd. When the front driveshaft turns when you put it in 4x4, the auto hubs click in. When you put it in 2hi and back up, they disengage.
    If you have auto hubs, and you can freely turn your driveshaft more than 3/4 turn in 2hi, your auto hubs are bad.
     
  16. BettyBurb

    BettyBurb Registered Member

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    I think the hubs are working OK. I just wasnt turning the shaft hard enough by hand. At 1/4 turn it gets hard to turn and then at about 3/4 they lock in. Turning the wheels by hand in reverse disengages. I took the hubs off and they look in perfect shape, nothing broken that I can see - but then I dont know what to be looking for. Both shafts have a little play with the hubs removed.

    Now that I am understanding how these hubs work, I cant see how one or both could have locked up. If for arguements sake one of them did lock up and the other did not, then could it cause the hopping and noise ???

    Could a bad hub lock up at random without the front driveshaft turning ???

    I will test drive again when I get some time. Before I took the hubs off everything seemed ok, I drove it around, backed up, around corners etc and no noise.

    I think I will grease everything, there are zerks on the rear driveshaft u-joints and front, but front should not be turning anyway. I'll lube everything ball joints, slip yokes, change differential fluid, transfer case, transmission and drive it some more and hope no reoccurance.

    Also, I think I will get the warn hubs. Do I need the spindle nut conversion kit too, or just the hubs ???

    Thanks for all the help
     
  17. TopOff

    TopOff 1/2 ton status

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    It sounds like your auto hubs were engaging for some strange reason. The autohubs need attention from time to time. IIRC they get a light coating of grease.

    My auto hubs do the same thing. When I turn the front driveshaft 1/4 turn or so it clicks, and turning it more the hubs engage. I love these hubs for when I hit the snow, just put it in four wheel drive, I don't have to get out. /forums/images/graemlins/laugh.gif

    If your front drive shaft CV joint is going bad (as opposed to U-joints within the front driveshaft), and your hubs are engaging making the front drive shaft spin, this front driveshaft will make this LOUD THUD every 1/2 to 3/4 turn.

    I had a bad front driveshaft that did this when I went slowly in 4 wheel. But above 30 mph it went away. I also had another front driveshaft that only made noise at higher speeds in four wheel drive.

    The front drive shaft CV joint runs ~$50+ and $50 for labor around here. Usually, when you take the shaft out, the driveline shop finds the sliding part on the neck to be bad too... now your talking a new front drive shaft... /forums/images/graemlins/frown.gif $250 + around here for a STOCK front drive shaft.

    Good luck with yours.
     
  18. Jeremy_C

    Jeremy_C 1/2 ton status

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    I'm having the same kind of trouble. The only time it thuds is when i get on it kinda hard. Would that be the same type of problem?

    Side note, the motor blew last week. I think the crank broke an slung a couple rods. That MIGHT have been what it was. I'll find out when i get the new motor in i guess.
     

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