Driveline Question

[76/85 Truck]

My truck vibrates around 55mph and the Four wheel drive shifter rattles pretty bad (because of the silver plate that rattles on top of the mechanism... I'm guessing it's to keep dirt out). And I noticed that on the trucks I've been looking at, the splines of the driveline are toward the transfercase.

On my driveline, the splines are toward the rear axle. Does it make a difference? Should I swap ends? I was thinking maybe this is causing it vibrate? I've had the tires rotated, wheels balanced, recently got new wheels and tires, and still, pulsing vibration around 55. Thanks for your help!

[87chevy.com]

Sounds like somethings not balance such as your tires. Have your tires balanced by discount or someone like that. As far a sthe drive shaft pointing one way or another, I wouldnt think it would matter... but you can swap it around for free right and see if it changes (doubt it will). If you balanced the tires already, you could double check to see if its a MPH problem or RPM problem. Like at 55mph your at just say 1800rpm, do 1800 rpm in a lower gear and see if you have that same vibration problem. If you do, you have something out of balance in the drive train, such as a fan blade, torque converter bolt missing/loose or drive shaft weight fell off. If the problem is with MPH, its most likely the tires out of balance.

clint

[76/85 Truck]

Thanks!! I took my truck out just now, ( i have a 350/350 combo) i can hit about 40 or so in 2nd gear, comfortably. As SOON as I hit the 30mph in 2nd gear, my shifter starts rattling like it does. (the whole truck vibrates, but it is really noticeable when the shifter makes that rattling noise) I shifted up to drive, and it stopped. What would be the first thing to check? I have no tach, so I can't tell the exact RPM or anything. Thanks so much for your help! Great idea!!

[76/85 Truck]

Could it possibly just be the NP203's chain drive causing the vibration throughout the truck?
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[87chevy.com]

so its a drive train issue for sure, check the fan blade to make sure your not missing one.... i was beating on my old 77 with a 454 and one of the fan blades let go.... i was a noob back then and didnt know what to check.. the PO gave me a hand and was like yeah, here is the problem... missed everything important check to see if your missing any weights on the drive shaft, see if your missing any tq converter bolts... other than that the 4x4 experts will have to chime in too
clint

[76/85 Truck]

Fan is nice and tight and all there, how would I go about checking the torque converter? Could it be a bad cluth on my fan? I don't think the driveline had any weights to begin with. Its been checked and spun before but that doesn't mean it's balanced now I suppose. Thanks for your help!!
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[76/85 Truck]

Maybe I'm wrong, but isn't the tq converter only held on by two sets of splines? Or is that for a different transmission?

[motornut]

my 78 burb blew a (1 of four)blades off and of course it took out both brake lines coming off the master/shook like crazy.....luckly i was able to coast to a stop.couldn't tell where at first the damage was fluid all over the place,and it was all new lines....and was surprised the vibration it caused .i heard after the four blade was a common failure,and it was changed to five,

how many blades?can you turn the fan blades ok?

[76/85 Truck]

Yupp, I can spin the fan... so the clutch must be okay? The clutch on the fan is making a whirring noise when I drive around 20, but I think that's normal. (I'm guessing that's what's doing it)... That sounds like my luck, motornut

Any other ideas on to why it's vibrating? It's not dangerous or anything, but is somewhat bothersome, for two reasons. The first being it makes it uncomfortable, and the second being I like to keep my truck as nice as I can . I'm going to keep this truck. My first rig ever, and I love it!!

Thanks for all your help everyone