Vibrations

75cj5. Just installed a rough country 2.5”. Now I have vibes. I went ahead and had my tires rebalanced and rotated, but to no avail. Driveline angles don’t look bad, lift came with 8 degree shims for rear. The one possibility is the shackles. Before the lift the shackles angled fore and aft. Now they are nearly straight up and down. Am I just feeling the tires maybe?

 

all the ujoints good? what kind of angles at each end ?

image stolen from another post

 

If your tires didn't cause vibration before they probably are not the cause after the lift. I know you want some angle in the shackles but i think that should fix itself after the springs break in and sag a little. I bet its the drive shaft. Just because they sent 8 degree shims doesn't mean thats the right shim for your specific vehicle. Get an angle finder and measure the driveline angles

 

Probaby is your driveshaft. shims under the rear axle may make it worse. Remember the pinion shaft and the main shaft of your transfer case must be parallel to each other but not necessarily in the same plane. With also as long as you have the u-joints phased the same you will have the best chance of no vibration. but the lift may have increased the overall angle of your drive shaft to the point it may vibrate anyway. If this is the case likely the only cure will be a double cardan joint next to the transfer case.

 

Are your front hubs locked?
Yeah shims don't make no sense... pull em out.

 

Check out Tom Woods 4x4. They know their stuff.


"...if your vehicle is experiencing drive shaft related vibrations after installing a lift, you should upgrade to a double cardan drive shaft."

https://4xshaft.com/blogs/general-t...le-cardan-drive-shafts-for-your-jeep-or-truck

 

Shims on the rear axle will REQUIRE a CV (double cardan) joint at the transfer case. And the drive shaft MUST be linear with the differential pinion.
This was just discussed on another thread!

 

I’ll check the angles. The rear is definitely not parallel. The shims are the cause in this case. So, if I aim for parallel angles, I’m headed in the right direction?

 

yes.

 

Not to hijack, but I wonder if that's the problem with my Dodge. Put a lift on it with some rear shims and since then it has a bad rattle (more of a heavy clunking like hiting potholes) under heavy acceleration. I should throw a camera down there some time and see what's happening.

 

Intermediates had bad angles to begin with (due to the Dana 20 t-case), but 2.5” lift shouldn’t put it in the impossible range. Take out the 8°(!) shims and see if the angle pointing up in the rear matches the angle pointing down at the t-case, with the angle of the driveshaft being the zero-mark. In other words, if you have a digital angle finder, set the angle finder at zero when it’s stuck to the driveshaft, then stick it to the pinion and stick it to the t-case output. Those numbers should match, or be within a degree or two.

 

I went with a double cardan shaft and transfer case yoke from Tom Woods.

 

This

 

Did you need to rotate and re-weld the axle perches? Doesn't look like fresh perches or welds in your picture. If so, wow that's would nice.

 

No, all factory except the springs of course and new shackles to replace what ever the previous owner put on for a lift.

 

I am thinking when using a double cardan joint you can use the axle shims if you like to reduce the angle of the driveshaft without fear of the vibration returning. maybe someone with better understanding can comment.

 

the pinion should be inline to the driveshaft
image stolen from tacoma world

 

Damn you!!! Why ya gotta show me cool stuff like this

 

Ha Ha!