Hey gang, My truck is all but undriveable due to a really bad vibration in the driveline. It is an all-stock '89 Xtra cab ADD 3VZE with 263,000 miles on it. The vibration occurs above 35 mph and gets exponentially worse with speed, but goes away immediately when coasting or with the clutch depressed. I feel no difference with engine speed, only vehicle speed, and it's the same in 2Hi or 4Hi. I crawled under my truck and found that the center bearing was shot, so I replaced it with a new one, but the vibration remains. All of the rest of the driveline feels good with no signs of looseness at any of the U-Joints, T-case flange or diff flange and everything was recently greased. The vibration comes through the seat, steering wheel, and gas pedal and is bad enough to send the body into a resonance. It feels like I'm driving on a washboard dirt road. I can accelerate moderately from a stop up to around 35mph with no vibration issues and I can free-rev the engine smoothly.
Since it smooths out with the clutch in, I have ruled out tires. I haven't ruled out engine or trans mounts since they wouldn't be loaded during coast, but I'm not sure that a bad mount would cause this severe of a vibration and I don't see anything physically wrong. Also, if a mount was the cause, it should vary with engine speed and load rather than vehicle speed. The driveshafts are all straight with no signs of damage.
I still need to remove the rear driveshaft and roadtest it in 4Hi, but the weather sucks and we have lots of snow and ice on the roads.
What am I missing? I searched the archives, but the only things I found were center bearing, and lifted trucks with angle issues. Could it be the rear axle? I don't hear any grinding or clunking.
My summer car is hibernating, so this is all I have to drive for the next two months. I keep it below 45mph by taking all backroads to work, but even at those speeds, the vibrations have to be hard on the truck. I need to find the root cause soon. <img src="/forums/images/graemlins/confused.gif" alt="" />
