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.

why the hell does my driveshaft keep breaking?

Discussion in 'The Garage' started by delta9blazer, Apr 23, 2003.

  1. delta9blazer

    delta9blazer 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    1,646
    Likes Received:
    0
    Location:
    Northern California, over by 7-11
    89, 350fi, np241
    4" lift kit was installed a few years ago. the shop that did it failed to make me aware that the driveline was almost all the way out of the driveline hole. the subsequent vibration tore up my 10b, which i replaced.
    i also installed a cv driveshaft, which didn't last long. it was rebuilt, and i decided to rebuild the 12b i just installed, to be safe.
    the driveshaft broke again (the centering ball @ the cv joint); it was pointed out to me that the 12b was angled wrong, so i had my spring perches rewelded, and the driveshaft rebuilt.
    the freaking thing is broken again, and i don't know why.
    i don't wheel the piss out of my truck, and i don't think 4" is a big lift.
    i could really use some help in trying to pinpoint a reason for all this.
     
  2. DuneRunner

    DuneRunner 1/2 ton status

    Joined:
    Aug 1, 2001
    Posts:
    1,252
    Likes Received:
    0
    Location:
    Fremont CA
    Are you running stock springs with lift blocks?

    If so you may what to stiff'n up the rear and add an Add a leaf.
    I don't know. I did a 2.5 block with 2.5 add a leafs. And nothing wrong with mine. not even a viberation. Just a thought! Like you mentioned you don't wheel the piss out of it. So you may not notice the difference in ride with the add a leafe.

    GOOD LUCK! KEN
     
  3. wayne

    wayne 3/4 ton status

    Joined:
    Feb 1, 2001
    Posts:
    6,178
    Likes Received:
    0
    Location:
    Carlisle, Pa
    Do you have any vibration when the shaft is working? If so you might have a bent output shaft on the t case. Also some people make cv shafts that are junk.
     
  4. BorregoK5

    BorregoK5 1/2 ton status

    Joined:
    Sep 7, 2001
    Posts:
    2,457
    Likes Received:
    0
    Location:
    San Marcos, Ca USA
    What kind of CV is it, a 1310 or 1330 CV? Many of the smaller CV's have tabs on the edges of them which limits the amount of angle they can opperate at and will cause the center locating ball to blow up the bushing in there if they contact. Blazers have hard driveshaft angles even with minimal lift so your probably running close to its capabilities. Who made the shaft?
     
  5. delta9blazer

    delta9blazer 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    1,646
    Likes Received:
    0
    Location:
    Northern California, over by 7-11
    a local place called driveline service of concord. i called and told them it was for a lifted blazer, and gave them the measurements.
    they've stood behind their product; they rebuilt it for me once because the gal told me the wrong place to measure, and at least twice due to failure caused by my 12b being pointed down too low.
    i certainly don't think these guys are the end-all and be-all of driveshafts, but i don't want to drop more cash on a high-angle-driveline special if there's a poblem in my truck that will damage it, also.
    the truck ran as smooth as it's ever run right after i had the rear end and shaft rebuilt. and again when i had the rearend re-angled and the shaft rebuilt.
    aaarrrrggggghhhh.
     
  6. Executioner

    Executioner 1/2 ton status

    Joined:
    Feb 22, 2000
    Posts:
    1,530
    Likes Received:
    0
    Location:
    Temp. Ft. Walton Beach Fl. home=Tucson, Az.
    ahum you are lubing the centering ball aren't you ?
     
  7. 91k5NC

    91k5NC 1/2 ton status

    Joined:
    Jul 12, 2002
    Posts:
    206
    Likes Received:
    0
    Location:
    Durham Nc
    after you get it fixed i would lower your t-case to take some of the angle off of it.
     
  8. delta9blazer

    delta9blazer 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    1,646
    Likes Received:
    0
    Location:
    Northern California, over by 7-11
    after the third rebuild, you betcha i was lubing the piss outta that thing.
     
  9. 83PJW

    83PJW 1/2 ton status

    Joined:
    Aug 18, 2002
    Posts:
    160
    Likes Received:
    0
    Location:
    leavenworth, ks
    just a dumb question not to insult your intelligence, but are all of your t case and u bolts tight? and is your tcase lowered like it should be with a 4 inch lift? also check your frame where your tcase blts in and make sure its not pushed up from trail damage.
     
  10. Leadfoot

    Leadfoot 1/2 ton status Premium Member

    Joined:
    Nov 28, 2000
    Posts:
    3,112
    Likes Received:
    1
    Location:
    Western Massachusetts
    [ QUOTE ]
    and is your tcase lowered like it should be with a 4 inch lift

    [/ QUOTE ]


    Not necessarily so. Match pinion angle to rear t-case angle. It will be more than stock and will wear out u-joints a LITTLE faster. Most aftermarket lift springs come with a shim that I remove or modify to match t-case angle. Lift blocks (modify to take out shim or necessary amount).

    Lift manufacturers shim the pinion up and tell you to drop the t-case.....reason why is it does alleviate the angle on the shaft (u-joint life), but mainly because it helps compensate for the added distance between the yokes after the lift, by tilting the pinion up and t-case down, you "gain" some of the distance you lost. Some people wouldn't buy a lift if they knew they had to buy a new/longer shaft, so they make is "possible" to lift your rig 4" and in most cases allow you to use your stock shaft (marketing.....$$$$$). Another reason for not dropping the t-case (especially with carburetors) is that it affects the floats (dropping the t-case tilts the t-case, transmission, and motor back), and puts the distributor closer to hitting the firewall. It can even put undo stresses on the exhaust components (remember the motor is tilted back and the manifolds/headers are attached, yet the rest ot the exhaust and hangers are held in the old location). I had a buddy that had a leak free exhaust until he dropped his t-case.....wonder why.

    Also lowering your t-case puts an even worse angle on your front driveshaft (which is much more than the rear angle to begin with).

    Many people do it, but it does not make it right. It is actually a good idea if you are a mall cruiser as you won't need to engage your front shaft. Six inches and more lift you probably need to do it just to avoid vibrations but then again with that much lift, you should run a HD rear CV, but $$$ is cost prohibitive to most.

    I run stock location t-case, 4" all spring lift (shims removed and stock perch locations), drive ocassionally to work 50 mile round trip at 75 MPH (no vibes), and truck pull (check sig). Even under abuse I have gotten over two years from my rear u-joints, granted it's a HAD shaft that is longer than stock (I knew going in that with 4" of lift I needed a longer shaft) with 1350 joints. I also lube them with every oil change.

    Again, not saying you can't or don't do it, but I don't recommend it...for reasons stated above. To each his own, and do whatever floats your boat. /forums/images/graemlins/thumb.gif

    To the original poster: What type of CV are you running (Caddy CV, HAD CV, etc.)? Also is the pinion now inline with the shaft, and when was the shaft last checked for balance AND runout. Runout can kill a shaft in a short amount of time....

    Good luck, hopefully you find the cause and a remedy.
     
  11. delta9blazer

    delta9blazer 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    1,646
    Likes Received:
    0
    Location:
    Northern California, over by 7-11
    a different driveline shop ID'd the cv as an older style gm model, probably from a caddy or something similar. the pinion is as straight inline with the shaft as possible on a daily driver, and the shaft was rebuilt when the spring perches were rewelded.
    the new shop said there doesn't appear to be any reason for failure, so it may just be a piss poor choice of where i bought the thing in the first place.
    the shaft is made to measurement, so i have no distance issue between pinion and output shaft. no angle issue to speak of (this from the driveshaft guy).
    i guess i'll give high angle a call, and drop the extra cash to get a stronger shaft made.

    thanks for the replies, i appreciate the hell outta this board.
     

Share This Page