Thread: Quick response please! Harmonic balancer

Tweet

My 1988 gmc 1 ton has a nasty vibration while driving down the road. It gets worse with speed. At first i thought it was the u-joints, but I replaced them and its still there. The vibration goes away when I pull the truck out of gear and let it coast. Also the vibration isn't constant but seems to be rythmatic with the engine rpms. Is it possible the balancer could be going? How do I check it? Engine only has 50000 miles on it.

Do you have a 2 piece drive shaft?

If so, are the u joints lined up correctly? Is the center support bearing good?
Check the converter bolts
And yes the harmonic balancer can along with all these other items cause the vibration

Jerry

Hell, I have exactly the same problem. I have changed everything from the fan clutch to the differential and it still isn't gone. Engine is rebuilt and balanced, new balancer, flexplate is straight, converter is new and trans rebuilt, driveshaft is brand new. Vibrating as always. Next thing I'm going to buy is a new trans mount from Energy Suspension, a harder one made of poly urethane. If it turns out to have been that (or the engine mounts, which I shall also be changing), then I'm going to be really angry
Please keep me posted if you find out the source of vibrations, and I'll fill you in on any news I have.
Good luck,
Max

I know that this might sound a little odd. But I had a 86 ford van that did the very same thing under the same conditions. If I put the tranny in neutral and coasted, there was no vibration. Under load it would about shake you out of the seat. Replaced the U-joints, carrier bearing, Balancer, belts and pullies. Still not any better. Then after driving it for a couple of weeks I needed to put new rear shoes on it and the axle bearings were wore out! I put new seals and axle bearings (and new RR axle) in the rearend and was amazed that it was the original problem. When it was under load the axle was twisting in the housing and trying to ride up the housing causing the vibration.

Well that sounds like an Explanation I haven't looked into yet, I know my rear axle isn't at its best anymore, I'll check that right next weekend... Thanks for the info!

Thanks guys! I've already replaced the ujoints and checked the carrier bearing while I was under there. Everything seamed good. Never thought about the axle. Truck only has 52000 mls on it but the under side is pretty rough. Who knows what the previous two owners really did with it. I'll try and check the rest out when I have time.