Odd shudder at 25mph

Installed a 1.5" AAL while waiting for my leaf packs to get here in order to compensate for having my new camper and a couple of other goodies in the back.

Now, when cruising at a steady 25mph there is an odd shudder through the whole truck and low rumble that matches the intensity and speed of the movement.

The ride/noise goes away as soon as you get over 30 and it doesn't track during high or low speed driving or braking.

There is very slightly increased steering input (might be me just being a hypochondriac, this is more than likely).

When installing the AAL I did have to leave one wheel/leaf pack attached so when raising the axle back up I did have to tweak the axle a little in order to get the alignment pin to line up correctly (about 1/2- 3/4" forward on both sides)

As I purchased the truck 4 months ago I couldn't tell you when the last alignment was done. Could this be the culprit and adding a leaf just compounded the problem?

Any input is greatly appreciated.

 

Check the driveshaft. If you're 4WD you can drop the drive shaft and run in 4WD. If the shudder goes away, the drive shaft is bent or needs balancing.

 

I've been chasing a similar vibration at that speed since I got my 96 last fall. It's all stock but it's got 260k on it. I'm almost positive it's the actual driveshaft. I've replaced the carrier bearing and a few u-joints and it got way better, but it's still there.

 

How much did you pay for the carrier bearing? Mine seems shot.

 

I don't remember honestly. Bought it from Rockauto. Probably under 50 bucks.

 

Be sure to check the angle of your u joints too. U joints at too high of an angle can shudder like that. If any of your rear u joints look too angled you can add some washers as spacers above your carrier bearing and see if it gets better.

 

This, don't go replacing your driveshaft or carrier bearing until you try this! Otherwise you're probably wasting your money on a part that didn't need replacing.