Fixed my vibration problem finally....

[OrangeCrush]

After many hours of trying to find my nasty vibration at 80-90mph, it was cured today.

After installing my fabtech 6" kit with specially included CV front driveshaft, I started to get this horrible shake underneath the truck chassis vibration.

I started off with getting the front supplied driveshaft rebalanced. It was terribly off. I had it rebalanced. I replaced the ujoints that came with it. I adjusted the pinion angle because on the rear of the front driveshaft, there was NONE. (still needs a little bit of adjustment for that part of it...no big deal)

I put the stock tires back on and still had the vibration. I even went to a tech friend of mine who placed a vibration sensor to the chassis. The program measures the frequency and oscillation of the vibration and determines and differentiates between wheel vibrations, driveshaft vibrations, etc, etc.

Again, I was told it was in the tires. I took my tires and had them rebalanced. Unfortunately, the computer balancer could only "static" balance the tires. Apparently unless I want to stick weights on the outside of the wheels, I have to stick them on the centerline which brings it back to being statically balanced.

There is a company in town that does what is called pad balancing. They mount the tire on the rim without weights and mark where the weight is needed. Then they dismount the tire, glue a weight that looks like a tampon pad on the inside of the tire and then remount the tire. At this point, it only takes 1 or 2 ounces instead of an enormous amount of weight.

Anyway, though I didn't have them pad balanced (yet) I had them rebalanced the old way and they were waaay off.

I had noticed that the rear driveshaft was pulled out of the trans by about 3/4" after the liftkit was installed.

So after trying everything else, I had a new rear driveshaft (1" longer and with a much thicker metal and diameter) made.

Magically, the vibration is gone. I have a small stutter at a much lower speed but I know it's from the need of fine tuning the pinion angle in the front.

For some reason, with the kit installed, the front driveshaft has a pinion angle off of the front diff but goes straight into the transfer case with no pinion angle. I lowered the diff to create more of an angle at the transfer case but it was small. I'm still playing with it.

Anyway, just thought I'd give an ending to my agonizing few weeks of bitching.

It seems to me that Fabtech should have either included this longer driveshaft or at least mentioned it may be needed. With the taper on the rear output shaft in the trans, it would have only been a minimal amount of time before it would have worn out the bushing and seals and started leaking.

Mark