94 k1500 350 vibration

[dmkilgo]

I just bought a 94 k1500 with a rebuilt 350 in it, and I'm trying to figure out why I'm getting some vibration around 55-60 mph. After playing with it some, I've noticed that the vibration stops as soon as I take my foot off the gas pedal (but I'm still going the same speed), so I'm thinking it must be something more related to the RPM at 55-60 mph in overdrive than the speed. Since it stops when I take my foot off the gas, I'm assuming that it's not the tires or driveline, because they are still spinning at the same rate. Could it be the engine itself? If so, what do I do to correct it? Anyone have any ideas? Thanks.

[Kudzupatch]

In high school I drove a Bronco that would eat u-joints. That was the sign one needed replacing. A vibration under load but I don't remember the speed range. If it were mine I would start there.

[pwdcougar]

Originally Posted by Kudzupatch

In high school I drove a Bronco that would eat u-joints. That was the sign one needed replacing. A vibration under load but I don't remember the speed range. If it were mine I would start there.

X2

Check the U joints.



Paul

[sntrym95]

X3. It's almost certainly the u-joints. After you replace them, have the driveshaft checked for balance. it's worth the extra $.

[Keith Seymore]

x4. Driveline disturbances are "torque sensitive" (that is, they vary based on load).

K

[dmkilgo]

That seems pretty definitive. Thanks for all the replies. Not sure how soon I'll be able to get it done, but that is where I'll start. Might get to it Saturday. I'll try to remember to update on whether or not that fixes it.

[mountie]

Do you only hear a vibration? Or do you also feel it?

In my transmission, during the early days, I had a bad LOCK UP in the torque converter.
That causes a vibration.... ( not really a noise)....

[dmkilgo]

You hear it pretty loudly, and feel it a little bit.

[dmkilgo]

Still haven't gotten to the u joints, but I've discovered another problem. Don't know if it is appropriate to make a new post, or continue the saga on this one, so I'll start here and if I need to make a new post someone please let me know. It feels like my four wheel drive engages, but the front wheels don't pull. I crawled under it and the actuator isn't wired up. It has 3 wires dangling from it. There are also three wires dangling on the other side of the axle that i assume go to it, but one doesn't look like it is the same color so I'm hesitant to hook them up. I also noticed another pigtail (a 2 wire) on the back side of the axle that is hooked up, but has one wire that is almost torn in two. Anyone know what it does? Any advice on how I should proceed with the actuator and wiring?

[dmkilgo]

Update: 4 wheel drive is fixed. Just wired it back up and all is well. Still haven't had time to install new u joints. The wife keeps assigning me other tasks. Need to get it done though. Deer season will be here soon...

[1976gmc20]

Originally Posted by dmkilgo

Update: 4 wheel drive is fixed. Just wired it back up and all is well. Still haven't had time to install new u joints. The wife keeps assigning me other tasks. Need to get it done though. Deer season will be here soon...

Those actuators are troublesome

I took out the actuator and stuck a piece of 3/4" PVC pipe about 1" long on the end of the plunger, and then reinstalled the actuator to semi-permanently lock in the front axle.

My pickup is only used for a firewood truck and on local roads, but you can also get a "Posi-Lok" cable control which eliminates all the wiring and the thermal-hydraulic actuator.