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help weird vibration

Discussion in 'Chevy Trucks' started by Big Red, Oct 7, 2002.

  1. Big Red

    Big Red Junior Member
    Messages: 13

    ok i have a really annoying vibration in my truck first off i'll give

    you the specs it's a '79 3/4 ton scottsdale it's got a 350/350 with

    full time four wheel drive 10 bolt front axle 14 bolt rear axle both

    with 4:10 gears for tires it's got 33x12.5x16 the problem starts

    at around 50-55 mph the only way to describe it is a rrrrrr rrrrrr

    rrrrrrr rrrrrr it only does it in high gear and gets less noticeable as

    you go faster but you can still feel it all the way through the

    driveline i've checked the driveshaft and it is straight but i haven't

    checked the tires for balance because i was told that if the tires

    are out of balance it would do it all the time not just in high gear

    at that speed. Could it be the tires or are the rims bent or is it

    something else? thanks for reading this and any replies would be

  2. Mike 97 SS

    Mike 97 SS Banned
    from U.S.A.
    Messages: 1,106

    Oversized tires are very noisy on the highway, i know that for sure. But if it only does it in high gear, id guess it would be a trans problem, or its only doing it in high gear cause that is when u reach the 50-55mph. You say you have to go 50-55 to make it do it, how about if you went the same speed but in one gear lower? Tires out of balance do start to vibrate right around the speed you mentioned anywhere from 50-60mph. Id still get the tires speed balanced, and put the 2 best ones, or the 2 which take the least amount of weights, in the front. The 2 tires that go in the front should match also i might add. Mike
  3. Pelican

    Pelican 2000 Club Member
    Messages: 2,075

    Did you check U joints?
    If it's full time 4x4, you'll want to check the steering knuckles too.
  4. SQRLY1

    SQRLY1 Junior Member
    Messages: 6


    I've got a 86 K20, and at work a 87 K30. They both have a similar vibration right at about 65MPH.

    It took awhile to track down. It's actually a combination of front ball joints and front shocks.

    It's really hard to see the play in the front ball joints visually.
  5. TLS

    TLS PlowSite.com Addict
    Messages: 1,425

    Big Red,

    I would get those tires balanced first. The faster you go, the more a few ounces can make a big vibe, ....BIGGER. Also apply parking brake and shift trans into -N- get a hold of the driveshaft, and stick your index finger into the U-joint area. Move the shaft around briskly. Any movement you feel in your index finger will show a bad u-joint. Also pay attention to the slip joint and the front U-joint.

    With it being full time you really need to look at the entire front drivetrain. On my '75, 55-60 is TOP safe speed. That thing really gets humming and vibrating. Always did! As a kid I remember my Dad being able to tell how fast my Mom was driving by feeling the vibrations!

    However, my old '76 was smooth as pie up to the tripple digits. It was a PT NP205 with 3.08's though!
  6. Big Red

    Big Red Junior Member
    Messages: 13

    i know it is not the u-joints because my brother-in-law had the same problem with his blazer and it was the u-joints so that was the 1st thing i did was replace the u-joints kinda disappointing when you think you have it figured out and it doesn't work i also know that it is not the slip joint because i had that checked too the front drive shaft can't be the problem because i drove the truck this summer without it on ( without that front driveshaft on it will sure do nice burnouts) the guy that i bought the truck from said right away that 2 of the rims were bent but the truck steers fine and drives nice so being a high school kid without much money i've been really hesitant to change the tires onto different rims that don't look half as nice as the ones that are on there just to find out that isn't the problem either

    i really don't want to believe the guy because he told me that the engine had just been rebuilt and warmed up a bit and only had 4000 miles on it when it threw a connecting rod so i got to buy it cheap with a blown motor all that was wrong with it was the bolts that screw into the torque converter from the flywheel were only finger tight once i got that taken care of the engine runs smoother than silk that is why i really don't believe him about the rims

    you guys have given me some really great suggestions and i can't wait till this weekend to check them out thanks alot for the replies i'll let you know if i get it figured out
  7. TLS

    TLS PlowSite.com Addict
    Messages: 1,425

    Big Red,

    Doing burnouts in a full-time transfer case equipped truck without the front drive-shaft isn't going to help your vibration. The Chain may have stretched and "could" be your problem.

    Get those tires computer spin balanced. If they have runout, the tire co will tell you.

    Also check the front axle steering U-Joints. They start whipping, and can definately cause this! With full time 4WD, even when you remove the front shaft, the whole front axle is still spinning (assuming you dont have lockout hubs?) and can cause this vibration.

    My guess is still those tires/wheels. Any friends or relatives with a new GM truck? Swap all fours with them for a little bit and see if it goes away!
  8. Motoman69X@aol.com

    Motoman69X@aol.com Member
    Messages: 37

    Did you check your rear end ? Make sure to check your pinion bearings. And that could cause your noise and vibe.
  9. plowed

    plowed Senior Member
    Messages: 344

    I would doubt that the bent rims could be causing it. Many years ago I had a 4X4 Toyota (that ate Chevies btw) and had a badly bent rim. It was bent so bad that on the highway one day I had a few people drive past me a tell me that my wheel was about to fall off. I never felt or heard any noise or vibration. The lugs were tight so I drove it a while longer till I got new rims anyway.
    Have you checked your brakes? I had a front caliper sieze up once and this caused some of the same sounds and vibrations.
    Good luck.

  10. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    Check the TCase bushing where the driveshaft slip yoke runs in,grab the driveshaft with truck in N and the wheels chocked/parking brake on it shouldnt move up and down much,it is normal to have some play but if its flopping around,Id change out that bushing,they tend to wear on high mileage trucks.Id also look into the rear eand as was mentioned,the ring/pinion gears may be on there way out.The fact that its only in drive is unusual,in drive ,the internal guts of the trans are locked up,and spinning as one,right thru as a 1 to 1 ratio,there are no planetarys spinning or clutches overrunning to make any noise.Maybe you cant get enough road speed in 2nd for it to happen.
  11. 90plow

    90plow Senior Member
    Messages: 739

    Turn the radio up!! haha
  12. Darren

    Darren Junior Member
    Messages: 1

    wierd vibe

    Hey Red i have a 85 two wheel drive that drove me nuts looking for a wierd vibration sorta like a pulse throught the vehicle at around 55 or so and it would go away some as the speed picked up. It was the tranny mount!!!! i put a new one in and the bad vibe went away. maybe this could help you.
  13. Big Red

    Big Red Junior Member
    Messages: 13

    well i think i might have found the vibration part of the flexplate was cracked and the bellhousing was cracked halfway across as soon as i get a different tranny and flexplate and put it all back together i will let you know after that it should run like a dream