Driveline Vibration Issues Please Help!

[Greenblazer-AZ]

Hey Everyone,
My rig has a new(rebuilt)'97 Vortech engine with 4 bolt mains and a factory roller cam(stock). It is however, topped off with an Edelbrock manifold and a Jet Performance Quadrajet NOT fuel injection. It has a TH350 transmission. both engine and trans have about 4600 miles on them and seem to be performing well. The NP203 transfer case is old and may be the culprit, but with all that lovely new horsepower my maximum speed is about 60 MPH, and I have a 3.73 gear ratio and 35" tires. I should be able to cruise at freeway speeds with no problem, but the vibration above 60 is really scary. It feels, and sounds like it's comming from the driveline and not the tires.

I do know that my front driveshaft is not balanced(it's been cut and sleeved to lengthen it), but I do have a part time kit and switchable hubs, however I have discovered that the front driveshaft is spinning when driving down the road even though it's disengauged. Is it normal for it to do this? I hope that this is the problem, but that's because a driveshaft is way cheaper than a transfer case.

I plan to take out the front driveshaft and see if that helps, but I'm still wondering if the driveshaft should be turning like that. I should also mention that the front shaft isn't turning at low speed. I had a friend visually check to see if it was spinning while I pulled forward at low speed. I am sure it was disengauged, but through the hole where the t-case shifter goes through I can see if the front shaft is spinning, and at highway speed it is definately spinning. I even tried a rubber bungee strap to try to keep it from spinning but it didn't hold it. Thanks for the help! /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/1zhelp.gif

Later, Allan Greenblazer.

 

[99firehawk]

I just had a horrible vibration that stumped me for a minute. First hing I would check is make sure all your tires are bolted on.Get the truck up to speed where it starts to vibrate and shift it to neutral, does it stop vibrating? Next check your u joints, crawl under the truck and grap the driveshafts move them updaon sided to side if they move they are junk. Now heres where I found my problem Upon checking my u joints I had about 1/2 of movement in the rear of the driveshaft, but it wasnt the u joint, some homw my pinion nut had backed off 3-4 turns makes for one heela of a vibration when the pinion gear is trying to feed itself to the ring gear /forums/images/graemlins/tongue.gif

 

[FWP]

Are you sure your front hubs are unlocked and working? Easiest way to tell, jack up the front of the truck, turn each tire around, the axleshafts should not rotate. That eliminates the hubs. The front driveshaft should rotate freely by hand when in 2wd, to confirm the t-case isn't engaging the front. If all that checks out, start looking at rear driveshaft angles, ujoints, slip joint, etc...HTH

 

[Greenblazer-AZ]

Thanks for the input Guys. I still have the burning question... Should the shaft be rotating if it is not engauged. I suppose that maybe friction is what's causing it to rotate, but is it normal?

Later, Allan Greenblazer.

 

[BadDog]

Friction will definitely make it turn.

 

[Greenblazer-AZ]

If that is the case then the problem is likely the front driveshaft vibrating. I'm gonna try pulling it out and test drive it on the freeway. Thanks, I'll let ya'll know.

Later, Allan Greenblazer.