wtf is causing this vibration? (1 Viewer)

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mountainmanryan

mountainmanryan

Joined
Jul 22, 2009
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Location
Colorado Springs
So about a week after the Christmas tree runs, my 80 developed a bad vibration that sets in around 45mph and gets worse as speed increases. At first it would only happen while accelerating, not coasting or braking. Have 230k on it so I changed all four u-joints on both driveshafts and made sure everything else was greased. Afterwards the vibrations decreased but not entirely. The amplitude went down but the frequency went up and now it occurs regardless of being under load or coasting. Switched out the soft snow tires for the harder summer tires but now I just feel it sooner, between 35-40mph. Just need help mak0ing a list of things to try and eliminate hopefully. Thanks.
 
Forgot to say that it seems to be drivetrain related, since the driver can feel it more than anyone else, but the entire vehicle shakes. Rebuilt the front axle last year, but not the rear.... Yet.
 
I had a really bad vibration in my FJ40 a little while back and it turned out to be the nut on the rear pinion yoke was loose. Check that, and check the yoke on the transfer case too. Turn your rear axle pinion yoke back and forth, it should have about enough play to turn maybe 3/8ths of an inch.

Inspect your driveshaft for any dents and check the splines in the shaft itself for play. It may have run out of grease.

Other than that, I would post on the Rising Sun web page. They have a lot of 80 guys that may know a common problem causing this.
 
If you are convinced driveline then the other things I would add to check are drive shaft balance (thrown weight) check diff, t-case and tranny fluids.
 
To verify that it is not your engine, when you feel the vibration and can safely do so, shift to neutral and shut off the engine when you are at vibration speed. Make sure you restart the engine. Check to see that you have clean rims. I had mud build up on my rims that gave me a bad vibration. Another time a tire shop swapped out some lug nuts on me. verify that all lug nuts on an axle are the same style/weight.

Good luck
 
LCPilot said:
To verify that it is not your engine, when you feel the vibration and can safely do so, shift to neutral and shut off the engine when you are at vibration speed. Make sure you restart the engine. Check to see that you have clean rims. I had mud build up on my rims that gave me a bad vibration. Another time a tire shop swapped out some lug nuts on me. verify that all lug nuts on an axle are the same style/weight.

Good luck
Click to expand...

Speaking of which, can I get an extra stock lug nut from you at the next meeting? I am missing one on the rear. Could that do it? It's not the rims. Summer tires are on different wheels.
Leon, what's the easiest way to check the transfer case fluid?
 
Make sure the truck is level and open the fill plug and feel the for the level with your finger. I don't recall the exact level but if you can feel it close to the bottom of the fill hole it should be ok. I can check the FSM if you don't find it on MUD first.

You also said at first it only happened while accelerating, is that before swapping the u-joints or that still happen sometimes?

Just occurred to me. You changed u-joints and the vibration lessened and changed. Did you put the drive shaft back in the same way you took it out? Is is out of phase?
 
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Have you checked the nuts on the steering knuckles? Though that's usually described as a wobble rather then a vibration - aka "death wobble".

How about the front wheel bearings? Any play when you pull @ 9 and 3 with the wheel off the ground?
 
I checked the FSM and the fluid capacity for mine is 1.8 qts. While flipping through the FSM they gave a troubleshooting order for vibration associated with propeller shaft 1) check for stuck sleeve yolk spline 2) propeller shaft run out 3) propeller shaft imbalance.

If you did not mark the drive shaft shaft ends along with the diff and transfer flanges they could be out of phase even if you have the front and rear phased. These are balanced as a unit. I always use match marks.

If you want to borrow the FSM you are welcome to it. Pictures and description are pretty good.

I'm hopeful this will be it. BTW Trevor has a good idea, hopefully you don't have issues front and rear.
 
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