Vibration Gremlin

[Franksmith]

1997 GMC
K3500 CCLB DW

I have a intermittent vibration while on the highway. It is there every time over 72mph. At lower speeds it comes and goes while towing or empty.

Brand new tires
Brand new top of the line shocks (helped a little)
Driveshaft balanced
1 new brake drum (helped a little)
Rag joint replaced with a U-joint

Front end parts good (inspected at reputable alignment shop)

There is spring slap (clunk) in the rear

I need help where to look next. Spring and A arm bushings?

HELP


Thanks

 

[evilunclegrimace]

Check your bell housing to block bolts and make sure that they are all there and tight. I just had a vibration develop on the 98 suburban that I bought from JackE's brother. There were 3 bolts missing and 2 of the 3 that were there were loose. Caused a vibration that would come and go.

 

[Franksmith]

I will check into the bellhousing, trans mounts, converter and flexplate since I am under the tow pig.

Thanks!!

 

[Oldblue98]

I had a experience years ago with a vibration gremlin that could not be located, it would come in cruising or low speed when under a load.. With all things being drive line thoughts for vibrations, sometimes people don't think of crankshaft run out or to check for it. My gremlin at that time was crank thrust bearings, and when under a load felt just like a u-joint / drive shaft etc. Just food for thought of things to check when the normal things have been eliminated.

 

[Franksmith]

I figured I would share and post the solution for my vibration issue.

Bad brake drums was the major cause of my vibration. I replaced the drums and then balanced them. The vibration is virtually gone. It still has a tiny vibration over 85mph haha. But she is 24 years old, 1ton, dually with the cheapest ($105/each) 10ply tires I could find.

Thanks for all the help on this