Rattle And Pop

[Backdraft]

OK guys, its time for me to break down and ask the pros for help on this one. I have, from the front end of my truck, a rattle and pop. The two are unrelated.

 

So first, the rattle. Its a rattling noise coming from under the front of the truck., Axle area. It almost sounds like the brake pads, but I'm not certain. Its most present at low speed when coasting. Around 20mph or so. When I ease into the brake pedal, it seems to go away. I have new rotors, new calipers, new pads, and properly installed anti-rattle clips. The kicker is that you can not only hear it, but you can feel it in the floorboard as well. I had this front axle, sans new brake hardware, under an XJ with short arms and seem to recall having the same annoying rattle.

 

And the pop. It usually happens as the truck turns a corner at low speed. Its a deep, heavy pop but very staccato and abrupt. It can be felt in the cab as well. Its also from the front end. All of the steering components are new. Drag link, tire rod, tie rod ends, steering stabilizer, and steering gear box. And all are V8 ZJ components. The track bar is a Rubicon Express HD adjustable. Recently the grade 8 bolt on said track bar sheared on the frame mount and has been replaced with another bolt and lock nut. I would like to point out that the joint on the frame end is a little odd looking. I can take a picture of it tomorrow and post if needed. The only thing in the front steering that is original is the pitman arm.

 

The only things that have not been replaced on my D30 are the unit bearings, u-joint, and upper control arm bushings. It couldn't possibly be any one of these making this racket could it? I'm kind of at a loss and its bugging me pretty bad, so any help is greatly appreciated.

[cruiser54]

How are your motor and trans mounts? Is your exhaust pipe rattling on the crossmeember?

[mvusse]

The pop is most likely the track bar. The track bar itself may be fine, but it is not unusual for either the hole in the frame side bracket or the one in the axle side bracket or both to become elongated allowing the track bar to move when enough force is applied.

 

Funny thing is (trying to track down the same problem in the past) is that the loud pop that can be heard and felt inside the cab is almost not audible when outside laying under the truck with someone else reproducing the sound.

[Akula69]

The pop is most likely the track bar. The track bar itself may be fine, but it is not unusual for either the hole in the frame side bracket or the one in the axle side bracket or both to become elongated allowing the track bar to move when enough force is applied.

 

Funny thing is (trying to track down the same problem in the past) is that the loud pop that can be heard and felt inside the cab is almost not audible when outside laying under the truck with someone else reproducing the sound.

 

Backdraft/Mvusse - I have the very same symptoms, and sounds in the '89. It is true its not audible outside (or under) the truck.

 

One difference though: Currently (because its about to go under the knife for a '89 to '99 swap and add 4WD) the front axle is solid w/o unit bearings (might eliminate some possibilities). It has a completely new front end including steering box, all ball joints, pitman arm, shocks, calipers/rotors/lines, steering dampner, track bar, tie rod and tie rod ends, new poly bushings on the tie rod ends and sway bar, new UCA and LCA. Even has a replacement track bar-to-frame mount bracket that we made sure did not have elongated holes ('cause the old one did).

 

We had been trying to track it down for over a year, and finally just agreed with ourselves that its the brake pads shifting in the caliper and called it a day. I'm hoping that when we swap in the D30 from the '99 it'll just go away.. :doh:

[Backdraft]

Cruiser - the motor mounts are a year old, but the trans mount is not. Didn't think about that one but thank you for pointing it out. I'll get under and check it.

 

Mvusse - I'm leaning toward the track bar also. I like the RE stuff, but I've never cared for the way it attaches to the frame bracket.

 

Jake - Best of luck on eliminating the noises with the swap. They are truly a pain to put up with!

[maddzz1]

If you have the RE HD trac bar it should be the double share one that comes with the HD bracket. I have one that I will be installing when i do my lift in the spring. I read before that the bracket tends to come loose a lot and some people actually weld it to the frame. If the bracket is loose that may be causing the popping noise even if the bolt for the trac bar itself is loose.

 

I also have a rattle that I can hear at low speed that gets faster when i gain speed, it can only be heard at lower speeds also. I'm thinking it may be the dust shield, since the pads aren't causing the problem. Does yours get faster as you gain speed?