Humming noise and vibration from truck. 92 C1500

[Scotty.92]

Hey guys, wasn`t sure of an exact category to post this in, but this seemed to be the closest to fit into.

I have 2 problems; 1 is a humming noise in the truck and other being a vibration.

Problem 1; A hum is usually found in the truck when I am cruising around town. Usually its between 20 - 40 km/h (Roughly guessing). Today I noticed at one point it hummed when I accelerated slightly and let off gas it it went away - comes back when you accelerate again or cruise around. (I don`t pay attention to the noise all the time but this time, this was what I noticed.) However, it was weird. This is because when I heard the humming noise I could feel in the floor pan shaking a little bit with my left foot when it hummed. I don`t recall it changing in intensity or sound. I just makes same sound except it either does it, or it doesn`t do it. For this, something is telling me that it is to do with the differential.

Problem 2: I have a vibration in the vehicle somewhere. This occurs around 80-110 km/h. I can feel this in the steering wheel, and its almost like a chatter feeling. Sort of like bup-bup-bup-bup-bup-bup kind of feeeling. Any ideas? I was feeling towards worn U-joints. Could this be the cause?

Any help would be GREATLY appreciated!

Thanks
-Rylen

 

[Scotty.92]

Help?

I found my u-joints are not bad, but the problem occurs with my slip yoke. I can move my slip yoke up and down, a little bit side to side. When I move the yoke up, there is a little gap in bottom of my trans seal (From the movement of the yoke) maybe between half the thickness to the thickness of a pencil lead. My driveshaft moves more than that and I figure this is making the sound in my truck.

-I drove the truck around more and noticed that the truck makes noise anywhere between 30km - 80km or so /h. Most notable around 40km/h. Makes a good clunk sound going between drive to reverse.. Vice versa.

 

[Ruger_556]

Clunk reverse to forward is going to be u-joints or diff trouble. The slip shaft usually has "some" play.

 

[Hood93z]

Mine had a very similar sound and the bolts for the trans bushing were loose I'd start there then work your way back and Check your universal then put you trans in Nutural then twist the driveshaft and push up and down on it