Wizbang

2001 4.0L, I ve been tryin to figure out whats causing a deep bass vibrations underneath the driver side seat at 25-35mph (its not taco bell). I just put in 4 in spring in the front, a 3.5 in add leaf, and 1.5in shackle, I feel like it could be a u joint or the transmission but I don't know. every time I almost let all the way off the accelerator, I get a rumbling that sounds like a tires rubbing, and when I barely push back down on the pedal the rumbling returns. Its not the tires, i took off the larger one and put the originals back on with the same outcome. Any help is very appreciated

evilxj85

get a tcase drop

KC10Chief

It's probably some drive line vibes from doing the lift. You increased the angle between your transfer case and your rear axle. You can get vibes from doing a lift. I have a 3" lift on my XJ and had some vibes, just as you're describing. I did a transfer case drop. It's cheap and easy and got rid of my vibes. Here's what you need.

http://www.quadratec.com/products/76006_801.htm

It took me about 20 minutes to install.

djlarroc

Yup. That's what it is.

Tcase drop, SYE, or bring the lift down to 2".