Driveline Vibration

[okleven]

I have a '73 Bronco that I have installed a 3.5" lift on, rebuilt the C4 transmission, transfercase, rearend, and installed a new driveshaft in the rear. The problem I have is a rythmic vibration that is especially noticable at high speed. It cycles every 2-3 seconds. I also hear a clunk when I hit the gas and also when I let off the gas. My first thought is that it is a driveline angle issue. Any ideas?

 

[admin]

Here are common things that could cause the vibration...

bad u-joint
loose drive shaft slip yolk
off balance drive shaft

Here are common things that could cause the clunk...

bad u-joint
loose drive shaft slip yolk
excess ring & pinion clearance

Hope that helps,

Dana

P.S. It could also be a combination of several of these items?!?

 

[davids78bronco]

okl, I'd run with your idea of the possible bad driveline angle. Is your driveline a 2-joint, or 3-joint? 2-joint being a standard driveline with a U-joint at each end. If this is what you have, then you need to make sure your rear Tcase yoke, and rear axle yoke are within 2 of each other, which means the rear pinion MAY need to be angled lower just a bit. If yours is a 3-joint driveline - that is, with a Carden-joint at the tcase end - then you need to make sure your rear axle's pinion is in-line with the main driveline tube

However, this isn't to say that the other suggestions aren't your problem either. Naturally, you've got some investigating to do

For the clunking you're hearing, you might want to double check your U-bolts, as they may have settled in a bit, and need to be re-torqued

 

[ken75ranger]

Sounds like a ujoint. Could be the springs. The second symptom sounds like axle wrap.

 

[ted_nicolas]

Driveshaft may not be fully balanced or out of balance due to worn U-Joints.
Check for a broken off tab (in yoke, keeps u-joint centered).
If broken off of one side of yoke, it may let the u-joint be installed
slightly off center, causing unbalance. Replace Yoke.

EXTREMELY LOW BUDGET, DRIVESHAFT BALANCING TRICK:
Buy two large radiator hose clamps (new, not full of grease or dirt).
Clamp them onto u-joint close together,
with the hose clamp heads about 120 apart from each other.
Drive and see if vibration is better or worse.
To fine adjust, loosen ONE clamp at a time, rotate it and retighten it.
Drive to check for vibration again.
If an adjustment gets worse,
you may put back where it was and try rotating the other clamp.
If it got better but still vibrates, loosen and rotate the same one again a little more angle away from untouched clamp.
This may take a while but eventually it WILL get balanced.
Sooner or later the combination of clamp rotations will dial it in.
This only balances driveshaft. It won't correct axle wrap or bad angles.
[email protected] B)

 

[Guest]

U-Joint it is! The joint that went into the transfer case yoke was sheared. I can't believe it stayed together! It had been acting like that for a while. It didn't have many miles on it. Maybe 1-2k. The Bronco hadn't been used for a while, though, so the grease could have gone bad.

 

[Broncoholics]

I'd have the driveline ballanced, new u-joints, new splines on the slip yoke and a CV on the T-case end. I added traction bars which helped big time. I never replace u-joints with 38.5" SX's! Make sure the pinion nut is tight and have good gear fluid.

 

[KROWBAR26]

Driveline angle is probably cooking the U-joint. I had the same problem when I went to a 3.5" spring lift. New Spicer U cooked in about 500 miles. Put on new rear axle with high angle pinion. Problem seems to be gone.