Is it my U-Joints?

[Mike_H]

OK I have done some searching, read my Haynes manual and I am still unsure. This is what is going on, over speeds of about 20-25 mph I get a nasty vibration under power. I mean if I am accelerating or climbing a hill I get a nasty vibration. It seems as if it is coming from underneath the truck. When I let off the gas and just coast it is gone and everything feels fine. I have gone under the truck and everything looks ok, there is no excess play in the driveshaft. I am thinking it is the u-joints, but I am unsure because of the visual inspection I did and I saw nothing wrong. I have never had to deal with a problem like this so I am unsure what it is.

My truck is a 92, 4x4, automatic with about 155k on the odo. Engine and tranny were both rebuilt about a year ago, and the front hubs replaced a month or so after. I am planning on changing the u-joints this weekend, please let me know if you think that it my problem also before I waste time and money on them.

Thank You
Mike

 

[Maniak]

If your rear u-joints are getting stiff (e.g. bad/squished/burned bearings) you can get the vibration you described...

You can eliminate/check the u-joints easily.. Assuming your 4x4 works....

#1, put your truck in 4x4 and lock the hubs (I haven't done this with auto hubs)...

Now drop the rear drive shaft.. Its only 8 bolts (they are 12 point 12mm I believe)..

Once you have it down.. see if you can move the u-joints around... If not, you know they are bad... Even if they are bad, you can drive your truck in 4x4 (front drive shaft only) and see if the feeling went away.. I don't recomend leaving it like this as it will handle differently.. For example, you will have lots of torque steer..

~Mark

 

[Skeets'91EB]

Yeah I would say its the u-joints. I have a 91, with 133,000 on it. Earlier this year I was experiencing the exact same problem. At speeds 25+, the truck would get a noisy, nasty vibration. It was taken to the shop and they diagnosed the problem and it was the u-joints. They replaced them and when I got the truck back, it drove just fine. Ask the shop to diagnose the problem before they work on it if you wanna play it safe or if you're still unsure. But, this is the same exact description of what happened to me back in January, so its gotta be the u-joints.

 

[Mike_H]

Thanks guys, that is what I was thinking, I am going to change them on saturday.