Thank you everyone for your replies. It looks like I have my work cut out for me now- I’ll make a list and start working my way through it.
The wheels are Wheel Vintiques Rallye wheels (new) and the tires are also new, however one or more may have developed a flat spot after the truck sat for a while on the tires. I have put over a thousand miles on it since the restoration, and the problem only appears on the highway at speeds above 60, and is exacerbated by any ripples in the road. It almost seems like a subtle wheel hop.
The custom driveshaft was removed and balanced (again), and it was found to be out of balance right from new…. Go figure. Some improvement with that.
I even replaced both rear axles with new, and all new bearings- no change in vibration.
It’s a 3.75 rear axle out of a GM metric blazer. Set up by a reputable rear axle shop.
The truck has a T5 trans that I rebuilt after the vibration was first noticed, with no change after the rebuild. The vibration is not engine-related, as it only occurs at speed, and there are no (unusual) vibrations from the engine at any rpm. When I removed the trans to rebuild it, I also had the flywheel checked again for balance- all good. I also checked everything with a dial indicator (flywheel running true on the crank, engine/bellhousing/trans alignment in both planes).
I am creating the list. From day one I have felt that it is wheel/tire related, and assumed that balancing with a “fingers” setup would solve it, as I have read that some Rallye wheels will not balance using hub-centric setup, due to issues with their manufacturing and the center hole stamping sometimes being off… it got a little better, but it is still there- and that might say a lot about where the problem is- most likely the wheel/tire combo.
I will say this- some of the wheels took a lot of weight to balance, and we had to put weight on the outside of the wheel as well, to get a decent balance. The tires aren’t huge- they are 215/75/15 BF Goodrich Long Trail T/A
If it is the tires, I am going to go with a set of new Coker steel belted radials that are narrower and larger diameter and have a bias-ply look to them ( The T5 has a pretty low first gear with my 3.75 rear end).
One more question: if the truck sat for 6 months on the new tires with that heavy stovebolt engine in there, and I have driven it over a thousand miles since, is it still possible that I may have some flat spots?? I have tried to raise the truck, slowly spin the tires and eyeball them, but I cannot really determine if there is a flat spot there, but to normal tire irregularities.
Thank you again,
Dave
