Knocking Sound When Turning Left

I've got a '90 MJ longbed 4.0 5speed, with 160k miles. Runs like a top, but I am getting a knocking sound whenever I turn left (turning into driveways, bends in the road, you name it.) It is very consistent, and it sounds like it is coming from underneath the cab of the truck, either underneath the seat, or my feet...almost like a paint can popping the lid under pressure.

I've been in no wrecks or major offroading thus far with it (only had it a few months), and this knock has been there since I got it - and it isn't getting any better or worse.

Any suggestions where to look to trouble shoot?

Thanks.

hmmm not too familar with MJs but does it do it when its in 4wd? I know that on an xj there is a double knuckle that is just about under where you sit on the front DS. there are 2 ujoints in there maybe them?? i don't know just tossin out ideas.

I haven't noticed it in 4wd. Just in 2wd.

The pop noise in mine was a loose track bar bracket, the one that's mounted to the frame on the driver's side. On my MJ you could look in the left front wheel well, and in front of the spring you could see where the bracket was shiny around the two bolt heads from the movement.

I´m assuming you have the 4X model. Sounds like the front axle shaft U joint. If you put the front axle on jack stands, turn the steering wheel some and twist the tire front and rear, you can often see the play at the bearing cap. I check mine several times a year, you can often see powdered rust by the rubber bearing cap seal, before there is much noticeable play. Klunk, klunk, klunk while your turning a corner, it´s usually time for a front axle U-joint replacement.
If it´s a single pop or knock, like MJmk mentioned the trac bar is worth a look. Most times at the ball type joint, at the frame mount. Though I did have the bottom mounting bolt, come loose on a YJ. Loose trac bar, usually makes for some play in the steering (wanders some).

Another development/more info:

Had the ujoints inspected/checked - they are good to go. The track bar is ok too.

On full lock/turning left (in 2wd) I get a binding/clunking sound that sounds like the front end is going to pop-

Also, my tcase lever is very hard to shift into 4wd (but it always goes in, and it seems to release when shifting back to 2wd.) The indicator light works perfectly, and I dont have the binding problem turning right.

I'm a 4wd system novice, but could this be vacuum/tcase related?

Thanks for the replies thus far, and again, any help is appreciated.

i wouldn't think that you turning would effect the tcase. cuz thats all in the drive line. and that does not change when turning. Do feel anything or just hear the clunking? as in steering wheel.

I can feel it under my feet/floorboard as well as hear it on turns at speed.

Just throwing some things out there. A single pop when turning into a driveway is a sign of a loose ball joint.
A ratcheting sound, could be the front axle shift motor (if your MJ has one). My old XJ with the 231 transfer, would sometimes hang in 4X (even with the indicator light out) and pop out at odd times. It´s pretty noticeable on sharp turns, things vibrate, rattle and the tires screech.
Like MJmk mentioned, a guy on one thread, was talking about worn control arm bushings, causeing a clunk.
My old YJ would pop at odd times, after I gave it a nose lift, on the spare tire, of the Jeep in front of me (please don´t stop, I´m sliding, boom).
If it´s a repeated klunk. klunk. klunk while turning, I´d have another look at the front axle U-joint. The play can sometimes be hard to see. Often a serious vibration at highway speeds.
When I have a hard time locating a vibration or noise, I often put it up on a lift, with a driver inside. Start her up, apply a little brake, and run things at a moderate speed. Being extremely careful of head, hair and limbs.
Could just be a body panel. stressed in an odd way, that pops.
Like CherokeeKid mentioned,the front driveshaft, U-joints (rear) usually require a special grease gun fitting, and are rarley lubricated.
Is it possible, you have some type of ratchet type locker in there? Under certain driving conditions, my locker makes some racket.

I had a wierd knock-knock-knock on turning with my '90 XJ. it would only happen at speed, or if I had rear seat passengers. Turned out to be the rear torsion bar mount hitting the rear wheel inside balance weights, causing a knock with each wheel revolution.
Couldn't figure out why I couldn't keep a wheel balance on this thing! I took several months to track this one down...the suspension had to be loaded just the right way, as in turning at speed.