1999 Sierra 43mph Vibrations

[Sierra54]

After having the transmission fluid flushed & filled with the dealer also dropping the pan to replace the filter I noticed a vibration that only occurs while accelerating through or while maintaining 43mph. This was my second trans service at 150,000. I now have 179,000. The previous searches I've done came up with this:

 

"35 - 45 MPH Vibration

There is a harmonic vibration as the truck passes through the 35-45 MPH

range. I have seen it blamed on defective exhaust parts, driveshafts, tires,

wheels, hubs, springs, shackles, u-joints, driveshaft pinion angle and the

carrier bearing. "

 

It sounds like a heat shield vibrating but I've tried removing and retorquing all of these bolts to no avail. Since this happened right after the trans service I'm not sure any of these listed is the culprit.

 

This is on a 1500 4X4 reg. cab, 5.3.

Any suggestions?

[gmtech4]

After having the transmission fluid flushed & filled with the dealer also dropping the pan to replace the filter I noticed a vibration that only occurs while accelerating through or while maintaining 43mph. This was my second trans service at 150,000. I now have 179,000. The previous searches I've done came up with this:

 

"35 - 45 MPH Vibration

There is a harmonic vibration as the truck passes through the 35-45 MPH

range. I have seen it blamed on defective exhaust parts, driveshafts, tires,

wheels, hubs, springs, shackles, u-joints, driveshaft pinion angle and the

carrier bearing. "

 

It sounds like a heat shield vibrating but I've tried removing and retorquing all of these bolts to no avail. Since this happened right after the trans service I'm not sure any of these listed is the culprit.

 

This is on a 1500 4X4 reg. cab, 5.3.

Any suggestions?

 

 

Iam a tranny guy at a dealership and have seen this a thousand times,1st ,the tranny svc did not cause this ,2nd,if it more noticable while accelerating,remove the rear driveshaft and move the u-joints,you WILL find a seized or a sloppy u-joint ,have a professional replace it ,take care,.ps ,the extension housing WILL crack and leak if not repaired soon,also seen a thousand times,cya,made lots of money doing them especialy Allison low/reverse housing,which is the adaptor,cya again.

[Sierra54]

Thanks for your input. I did have a new NAPA greasable u-joint put in after the original went out in the rear. This was probably 50-60k prior to the vibration beginning. I have always greased it with Mobile 1 grease at every to every other oil change. The front is original and sealed. I had a new front pinion seal put on about 15k ago. Would they have been likely to have missed a bad u-joint when doing this?

 

I guess with this many miles it could be either. I thought they may have bent a linkage out of the way to get the trans pan off and this could cause the vibration. I guess with this many miles it I shouldn't complain and take care of it before it ends up costing me more to fix.