Shaking problem

[1979C20]

 I developed an issue today. I drove my truck to work with no issues. When I left, i noticed a strange shaking that ive never felt before. Its only when im slowing down, it doesnt matter if.my clutch is in or out, brakes on or off, coasting to a slow stop or stopping quick, between 35 and 25 mph only, the whole cab of my truck shakes pretty dang bad. I crawled underneath it when I got home and I noticed my tranny mount bolts are missing and that my tranny was slid over 2 or 3 inches to the left. So im thinking that either my transmission is bouncing around a lot, or if because it was shifted over, if maybe my u-joint is shot. Is there a way to check if the u-joint is the problem other than replacing it? Does my issue sound like a u-joint? Thanks in advanced, and yes, im going to get my tranny mount all buttoned up.

[bake74]

     The way to check your u-joints.  Hold one side still, try to move the other side, any movement, they are bad.

[thirsty]

Sounds like a loose wheel, wheel bearing, or a soft tire to me. Bad universals will usually vibrate instead of shake.
Put some bolts in the transmission mount and check it to make sure it is not bad then you can just check the universals for play with a bar or large screwdriver.

[firefighter]

Bad news about the tranny mount. That should be relatively straight forward to fix.

I've had small bulges (caused from a broken cord I think) in tires that can cause the type of vibration you are speaking of.
Check all 4 closely.

[bake74]

     Thirsty and firefighter are right.  I always check tires first. ( tire separation, or throwing a weight ) will cause shakes.  Also I have had two (heavier vehicles ) with warped rotors cause shakes at certain speeds, regardless if I was speeding up or slowing down, and always at a given range of speed.

[Irish_Alley]

yes check tires for missing weights. check for clean spots on the wheels where the weights used to be, inside and outside. and busted wires can cause shaking but i think thats at all speeds

[1979C20]

The shaking started at 35 and stops at 25 only while im slowing.down. It doesnt shake while I accelerat or coast.during those speeds. The shaking starts at the cab, pretty much right at the bed gap. The bed does not shake, but my cab and my hood shake like crazy. Its almost like my ujoint is bad causing a vibration, and since my tranny mount is shot and my tranny slid.around, its resting against the trans tunnel and the ujoint vibration is going through the tranny and shaking the whole truck. Ive noticed more and more vibration in the shifter over the last month or so. The tires were the first thing I checked. All have good pressure and none are misshapen or worn weird.

[bd]

When your trans shifted 2-3" it altered your driveline angles.  Fix your trans mount and your problem may go away.  But, do it sooner than later so your your problem doesn't escalate to include a broken bellhousing and/or broken fan shroud.  While you're at it check your motor mounts.

[1979C20]

Motor mounts are good, and the bolts from the bellhousing to the engine are nice and tight. I made sure of that when I noticed the tranny was shifted. Im going to get bolts into the tranny mount today and see if that fixes it. While im down there im going to check my ujoint and replace it if necessary. Ill let you know how it all goes. Thanks for the help guys.

[Irish_Alley]

Never have I had a problem with drive lines causing vibrations. That's kind of like saying lifted truck will vibrate. I've had bad mounts and the only way I knew was a clunk while shifting. The drive shaft weight could of fell off also. But let me get this straight its been vibrating for the past month and you just now are trying to fix it. The bolts probably fell out due to the vibration

[87454westernhauler]

i would bolt the trany cross member back in befor u drive it much more!

[1979C20]

No, it was just a slight vibration in the shifter. But this is shaking the whole truck. I had to pay rent today, so I wont have any money till tomorrow, so I buy some tranny bolts anf get that tightened up, and if its still vibrating, my u joint is still under warranty so Ill swap that out. If both of those dont solve it, ill have some investigating to do.

[bake74]

Never have I had a problem with drive lines causing vibrations. That's kind of like saying lifted truck will vibrate. I've had bad mounts and the only way I knew was a clunk while shifting. The drive shaft weight could of fell off also. But let me get this straight its been vibrating for the past month and you just now are trying to fix it. The bolts probably fell out due to the vibration

     I have had drive lines cause shaking, but only on extreme lifted trucks/jeeps where the drive lines were at extreme angles and not balanced.

[Irish_Alley]

Never have I had a problem with drive lines causing vibrations. That's kind of like saying lifted truck will vibrate. I've had bad mounts and the only way I knew was a clunk while shifting. The drive shaft weight could of fell off also. But let me get this straight its been vibrating for the past month and you just now are trying to fix it. The bolts probably fell out due to the vibration

     I have had drive lines cause shaking, but only on extreme lifted trucks/jeeps where the drive lines were at extreme angles and not balanced.

thats what i mean lol. but 79 you can buy any bolt from the hardware store for under a dollar. i would almost say around 30 cents

[1979C20]

My u joint is shot, gonna swap it out today. And my tranny mount is screwed, the bolts are through the crossmember, but the tranny is still shifted, so I have to.get a new one. Thanks for the.help guys.