Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Need help with driveline noise

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BigJohnson, Jun 24, 2001.

  1. BigJohnson

    BigJohnson 1/2 ton status

    Joined:
    Jan 22, 2001
    Posts:
    207
    Likes Received:
    0
    Location:
    AL
    My Blazer makes a loud clunk when I accelerate and when I am rolling and let off the gas. I have had it in a shop and they said it was the rear axle. What is the best way to find the noise, and how do I check the rear axle for wear? Any help would be greatly appreciated.
     
  2. UseYourBlinker

    UseYourBlinker 1 ton status

    Joined:
    Jun 7, 2000
    Posts:
    11,117
    Likes Received:
    0
    Location:
    .
    I would start by pulling the diff.cover off,and check for any broken teeth on the gears.


    <A target="_blank" HREF=http://community.webshots.com/user/vwryda>http://community.webshots.com/user/vwryda</A>
     
  3. newyorkin

    newyorkin 1 ton status

    Joined:
    May 8, 2001
    Posts:
    16,555
    Likes Received:
    157
    Location:
    Los Estados Unitos
    If you get the clunk in acceleration, I'd guess it's the slip yoke at the transfer case, if you have one in an '82 (was that fixed yoke?). Also check all your mounts, motor, tranny. Check U-joints. These are probably all things the mechanic checked, but it doesn't hurt to go over yourself also. If you're hedgy about pulling the cover off the diff, try this: find a level surface. Set the parking brake, chock both sides of the front wheels, put her in nuetral, and try to rotate the driveshaft both ways by hand. If you have to jack it up, make sure everything is chocked against rolling!! The parking brake should hold it from any real turning, but you should be able to get an idea of how much play you have. If it's a lot, then that's probably truly the source of your clunk. Do a search, the clunk has been a big subject around here.

    Ratch
    **<A target="_blank" HREF=http://k5.8m.com>http://k5.8m.com</A> What more is there to life?**
     
  4. bigblue

    bigblue 1/2 ton status

    Joined:
    Dec 6, 2000
    Posts:
    658
    Likes Received:
    0
    Location:
    southern california
    Same thing happened to me and it was the Motor mounts...
     
  5. muddin4fun

    muddin4fun 3/4 ton status

    Joined:
    Feb 19, 2001
    Posts:
    5,644
    Likes Received:
    0
    Location:
    N Texas
    I would also check all the mounts first.

    <font color=purple>Have you hugged your K5 today?</font color=purple>
     
  6. How can you visually tell if the motor mounts are bad? I have looked but the just look like mounts to me, I a novice at these kind of things

    '84 K5

    Chevy in my blood.
     
  7. 89Blazin

    89Blazin 1/2 ton status

    Joined:
    Mar 20, 2001
    Posts:
    134
    Likes Received:
    0
    Location:
    midwest KC area
    Sure sounds like u-joint...

    85 Burb and an 89 Blazer
    One just for fun, one simply for pleazer
     
  8. BigJohnson

    BigJohnson 1/2 ton status

    Joined:
    Jan 22, 2001
    Posts:
    207
    Likes Received:
    0
    Location:
    AL
    Thanks for the replies everyone. I have pulled the diff cover, no missing teeth or anything, everything looks normal. I got someone to switch it from reverse to drive while I listened underneath. When shifted into drive the driveshaft would turn about an 1/8 of full revolution before stopping. Does this mean the rearend has too much slack in it? I think some of the noise is coming from the rearend, but I think the transfer case is making a noise where the driveshaft comes out of the rear. What could be making that noise and is there a way to check it for damage?
    Thanks again for the input.
     
  9. newyorkin

    newyorkin 1 ton status

    Joined:
    May 8, 2001
    Posts:
    16,555
    Likes Received:
    157
    Location:
    Los Estados Unitos
    Noise at the transfer case, I'd say the infamous New Process 208 output shaft/slip yoke clunk, but going by your profile, you're in an '82 with a th400 tranny, and I'd suspect you're using a 203/205 transfer case, which I'm sure is a fixed yoke unit (205 slip yoke or fixed guys?). There should be a badge on the case identifying it. Stick that in your profile to help us get some more info to work with.
    Your rear is what gives the driveshaft resistance, so if you're seeing some initial rotation in the shaft while holding the brake, you definately have some wear in the rear. You can do another easy test that I just remembered doing in my truck; go to an incline and drive up it a little bit, then brake, go to nuetral, let it roll backward a few inches, brake and hold again, and put it back in drive. If it's the gears, then the clunk will be much quieter because you've kind of pre-loaded the slack in the gears. Do this same test again but then put it in reverse instead of drive. Your clunk should make the truck jump then.
    1/8th is a lot of rotation. That's enough to really beat up your motor/tranny mounts, and possibly start hurting the tranny during normal driving (constant impact-like engagements). You may want to start considering some diff upgrade options though...

    Ratch
    **<A target="_blank" HREF=http://k5.8m.com>http://k5.8m.com</A> What more is there to life?**
     
  10. newyorkin

    newyorkin 1 ton status

    Joined:
    May 8, 2001
    Posts:
    16,555
    Likes Received:
    157
    Location:
    Los Estados Unitos
    AZBlazeman, it's not really easy to tell unless the mount is really chewed up. Mine just happens to be dried out, seriously cracked, and is starting to look a little torn up.
    The real way to tell is to have someone put as much braking power (parking, hydraulic pedal) on the truck as possible, and rev it in gear while watching the particular mount you suspect (or all of them). There should be some flex in the mount itself, but no seperation or over-compression of the rubber (or whatever the particular mount is; I started making them out of steel for my Mopar years ago after I went through about 10 in a month...).
    You'll probably be able to tell what's too much.

    If you don't have any help, you can do it with a jack, too. Chock all the wheels, and put a block of wood on the jack, and try jacking the transfer case to check the tranny mount, oil pan for the engine mount (make sure you use a large piece of wood so's not to center too much force on the oil pan). You should be able to tell if a mount is shot. I just started spraying all mine with silicone to keep the rubber moist, and I think it's doing good on the motor mounts!

    Ratch
    **<A target="_blank" HREF=http://k5.8m.com>http://k5.8m.com</A> What more is there to life?**
     
  11. BigJohnson

    BigJohnson 1/2 ton status

    Joined:
    Jan 22, 2001
    Posts:
    207
    Likes Received:
    0
    Location:
    AL
    Thanks for the help newyorkin. The transfer case is an NP208 with a slip yoke. How can tell if the slip yoke is making some of the noise? As for the rearend I will try what you said and see how it goes.
    Thanks again
     
  12. newyorkin

    newyorkin 1 ton status

    Joined:
    May 8, 2001
    Posts:
    16,555
    Likes Received:
    157
    Location:
    Los Estados Unitos
    No problem!
    The best way I've found, and many others here, is to pull the driveshaft out (get a bucket to catch the ATF from output shaft when you do this), spread a couple wads of grease inside the splines, put the shaft back in, and see if the clunk is gone or reduced. This was enough of a problem with GM for them to put out a Technical Service Bulletin. There is a special grease that will last longer, but I think it's super-expensive, and still wears out anyway.


    Ratch
    **<A target="_blank" HREF=http://k5.8m.com>http://k5.8m.com</A> What more is there to life?**
     
  13. ftn96

    ftn96 1/2 ton status

    Joined:
    Sep 26, 2000
    Posts:
    3,238
    Likes Received:
    0
    Location:
    Nashville Tn
    If the grease in the slip yoke fixes the noise, it will last a few hundred miles. You could go buy that expensive grease, but like Yorky said, it will come back. If this is the case, your slip yoke is worn out. option A, get a new yoke, opt B, keep packing it with grease till you go back to option A..[​IMG]
    Now the clunk when engaging drive and reverse, I sorta dis-agree with Yorkin. I have a fresh rear end (new carrier, new gears, axles are still stock) and I still get the 1/8 turn and the clunk while engaging drive and reverse.
    Here are my theories.
    A, the axles shaft splines are worn out and they are loose inside the carrier. SO getting new axles would fix this. Will let you know when I get that far.
    B, the slop is coming from within the transfer case. It is chain driven and chains do stretch.
    I tend to lean towards option B. But I have not confirmed this yet.

    Steve Fox for President, 2004.
    Jimi Hendrix was re-incarnated in 1990 as my....JIMI
    <A target="_blank" HREF=http://www.nashvillek5.freeservers.com>http://www.nashvillek5.freeservers.com</A>
     
  14. newyorkin

    newyorkin 1 ton status

    Joined:
    May 8, 2001
    Posts:
    16,555
    Likes Received:
    157
    Location:
    Los Estados Unitos
    Ahh, good point ftn, always thinking gears I forgot about the axles... THAT makes some sense.

    The transfer case is pretty much direct drive from the tranny to output shaft though, so if it were chain wear, it would only clunk the front axle when in 4. But it also would not rotate the pinion yoke against the brakes, that has to be something inside the rear.
    You can check for chain wear on a 208 visually; open the top filler hole and shine a flashlight in there (move it around until you can see the chain). Rotate the front driveshaft back and forth to visually watch the slack take up and let out in the chain (unlock front hubs for manual hubs, might have to raise front wheels for automatic hubs). A little slack is acceptable, but too much is bad. maybe 1/8 inch up and down movement? Anybody have any thoughts on that?
    ftn, is it possible the lash is not set right on your new gears? Logically, I'd guess a pinion that's not shimmed up real tight might show the same symptoms as significant wear in the r&p. Just a thought...


    Ratch
    **<A target="_blank" HREF=http://k5.8m.com>http://k5.8m.com</A> What more is there to life?**
     
  15. ftn96

    ftn96 1/2 ton status

    Joined:
    Sep 26, 2000
    Posts:
    3,238
    Likes Received:
    0
    Location:
    Nashville Tn
    Well, When I set up my front and rear I had set the lash to be real tight, I mean almost ZERO, Cause at the time I didn't know what the lash was really for. I thought it adjusted the slop. But come to find out this is partially correct but with no lash your gears dont get lube to the teaath contact surface thus they over heat. But while I was test driving it around with next to zero lash I still had the same drive adn reverse engagement clunk. So Im gonna have to say that I dont think that is the problem. Anyhow, I re-set the lash and set it up properly at .008 like stamped on the gears. The only other thing is the carrier bearing pre-load. If it is not enough it will allow your lash to open up and close under load. So I made sure it was in there real tight. I actually added .010 preload to each side of my carrier. .005 more than specs. So I dont think that is the deal either. Which leads me to think that it has to be in the worn out axles (splines) or the worn out slip yoke splines.
    Im ordering a new CV Slip yoke driveshaft from Tom Woods. Mikey (captcrunch) said when he put his on he didn't think it was going to fit on cause the splines were so tight.
    I am hoping this new yoke on the new shaft will eliminate this problem. If not we will try the new axles shafts, which I want to get anyway.
    But I forgot the T-case chain only works the front. My bad there.
    Anyone want to buy me some new Moser moly shafts to help in my theory?[​IMG]

    Steve Fox for President, 2004.
    Jimi Hendrix was re-incarnated in 1990 as my....JIMI
    <A target="_blank" HREF=http://www.nashvillek5.freeservers.com>http://www.nashvillek5.freeservers.com</A>
     

Share This Page