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Cv shaft and vibration

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by ftn96, Oct 18, 2001.

  1. ftn96

    ftn96 1/2 ton status

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    Well, not that I have my 36's on an underlying vibration has been awakened. I guess when I was running the 33's and the 4.56's the drivshaft was zipping right on past the vibration right at take off.
    I set the rear angle to 2 degrees like Jesse suggested. But now that the 36's are one its not zipping right on past this vibration area. Its right when I take off up through about 10Mph then it goes away.
    So now to my quesiton, Should I add 1 more degree of shim to bring it to 1 or should try and maybe do 1/2 degree?

    Surgeon General's Warning:
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  2. Triaged

    Triaged 1/2 ton status

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    I would go the other way...you are prob getting more axle wrap w/ the larger tires causing the pinion angle to be off under acceleration. Have someone drive along side you and look at the pinion to see if it rotates up too far.

    '71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
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  3. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I don't think your driveshaft is your problem. Sure you don't have a broken motor mount? Trans mount?

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  4. Executioner

    Executioner 1/2 ton status

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    Ask jessy, put the 33 back on !
     
  5. DPI

    DPI 1/2 ton status

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    What kind of tires did you get? I put 36" TSL Radials on mine and they will vibrate you to death at lower speeds.

    4.56 Geared, Power Locked, Dana 60
    4.56 Geared, TSM Disc Braked, Detroit Locked, Corporate 14
     
  6. ftn96

    ftn96 1/2 ton status

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    They are the 36 TSL radials. At first I was sure it was the tires. But if I just let off the brake and let the motor pull me at idle it will almost immdeiately start vibrating until I get up past 10 Mph.
    Also, If I pretty much punch it, it goes through this vib zone real quick. And it comes back as Im nearing a stop from 10 mph down to zero.

    Surgeon General's Warning:
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  7. ftn96

    ftn96 1/2 ton status

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    Yes, Im sure the motor mounts and the tranny mount are new, w/ less than 3000 miles on them.
    Any more ideas anyone?
    Im gonna call Jesse today and see what he says.
    Normally I wouldn't worry about it, but in the range where this devil lives is about where Im gonna be when Im wheelin, and I dont want to be having that vib rattling me to death.

    Surgeon General's Warning:
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  8. Yake it out to a flat smooth fiel and see if it still vibrates at these speeds.That way you can tell if its the tires on the pavement or something else.My 82 did this and it ended up being just the lugs hiting the pavment at lower speeds.
     
  9. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    Could be a number of things. First check your pinion by having someone get in your rig, set the parking brake, put it in gear, and slowly step on the gas. Watch to see how much the pinion moves upward (shim as necessary). I have heard the tire lugs can sometimes cause a weird vibration at certain speeds (even if tire is balanced). You may also want to calculate RPM's/MPH. What I mean is if it is a drivetrain problem it will usually happen at the same RPM regardless of tire size. Find out what MPH/RPM is does it now with 36's and translate that to your 33's. Put your 33's on and see if it happens in the calculated RPM/MPH range. Use RPM's = (Gear Ratio * MPH * 345) / Tire Diameter for autos and RPM's = (Gear Ratio * MPH * 336) / Tire Diameter for sticks to calculate. Remember your Gear Ratio is going to be your rear end Gear Ratio times your tranny gear ratio. I assume since you hit it at 10 MPH you are still in first gear. So if you had 4.10 rear end gears and a TH350 tranny (which has a 2.52 first gear), the gear ratio you would use for the formula is 10.332.

    GM Automatic Transmision Gear Ratios

    Transmission Type 1st Gear, 2nd Gear, 3rd Gear, 4th Gear
    Power Glide 1.76 or 1.82, 1.00
    TH350 2.52, 1.52, 1.00
    TH400 2.48, 1.48, 1.00
    700R4 3.06, 1.63, 1.00, 0.70
    200R4 2.74, 1.57, 1.00, 0.67
    4L60E 3.06, 1.63, 1.00, 0.70
    4L80E 2.48, 1.48, 1.00, 0.75

    I don't know the manuals off the top of my head but you should be able to find them on the web if needed.


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  10. ftn96

    ftn96 1/2 ton status

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    Now that I think about it a little more. It does it up to the point where it shifts to second gear. then no more. But that could be just coincidental that at 10 mph (when it goes away) thats where the vacum gets great enuff to change gears.

    Surgeon General's Warning:
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  11. drivelineman

    drivelineman 1/2 ton status

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    it could be axle wrap? please take a pic of your pinion angle and send it to me- i'll call you today-jess

    Owner of High Angle Driveline http://highangledriveline.com
     
  12. ftn96

    ftn96 1/2 ton status

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    It will have to be later this afternoon. My camera is at the house.

    Surgeon General's Warning:
    Viagra and steroids may be harmful to your spouse![​IMG]
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  13. HarryH3

    HarryH3 1 ton status Author

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    Sounds like it's just your tires. Big, knobby mud tires vibrate like crazy at slow speeds. It's those big lugs whacking the pavement. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
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  14. ftn96

    ftn96 1/2 ton status

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    It very well could be. These are the 1st TSL's I've ever owned. And to eliminate the tranny I started in neutral on a hill and costed and it still vibs. This also eliminates axle wrap.
    So I either screwed up my angles when I welded the perches (which I highly doubt) or its the tires.

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  15. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    It's the tires...

    Rene

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  16. DesertDueler

    DesertDueler 1/2 ton status

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    Mine does the same thing. My is because the pinion angle is off. It vibrate when you get going, but stops after 10 mph. The the drive shaft turns smoothly on mine. Check to see if your drive shaft is wobbling while it turns.

    86Jimmy 4"&35"MTRs,87 burb 4"&35"MT,69Firebird w/525 hp,and 70GTO live in PHX,AZ<a target="_blank" href=http://www.geocities.com/modifierperformance>My vehicles</a>
     
  17. ftn96

    ftn96 1/2 ton status

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    It shouldn't wobble. Its brand freaking new.

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  18. Pugsley

    Pugsley 1/2 ton status

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    I'm leaning toward tires too, but just for kicks, check your trans mount for any signs of ATF or oil on it - the one piece (85-up) mounts turn to crap once they get soaked.

    Of the 5 toughest dogs in the neighborhood, my cat's ranked #3
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  19. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    I wasn't trying to eliminate just the tranny. I was trying to rule out driveline (tranny, driveshaft, u-joints, pinion angle, etc.). With the trans in nuetral and the wheels spinning, the driveshaft is still turning. Pinion angle is probably elimated though because when coasting the pinion rotates down (or stays the same) and under acceleration it rotates up, since it still does it while coasting I don't think that is your problem. This would narrow it down to driveshaft inbalance, bad u-joint, or tires. Considering it doesn't do it at all with the other tires, I would have to say it is just the nature of these tires (as others have stated). Hope this helps, good luck.

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  20. ftn96

    ftn96 1/2 ton status

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    Well, here is exactly what it feels like. It just came to me.
    You know when they are doing road construction and they grind up parts of the old pavement and it leaves that REAL ruff texture? You know how it feels when your driving on that? Thats exactly what it feels like.
    I also noticed that this morning it wasn't as bad until (Im assuming here) that the tires got warmed up.

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