"Popping" noise while climbing in 4wd...

[meatplow5150]

While climbing in 4wd, I noticed an intermittent "popping" or "knocking" sound.
I have a 4 1/2" Rusty's lift, 3/4" spacer, adjustable UCA's and LCA's, Rusty's H/D trackbar mount, and a engine/transmission skid plate, also from Rusty's (recently installed).
After closely inspecting the underside, I noticed that it looked like the front driveshaft had been moving to the right enough to hit the belly plate. You can't see it in the pic, but there are rub marks on the shaft yoke as well...

...I also noticed a gouge all the way around the slip joint, and the grease zerk got knocked-off...

It seems painfully obvious to me WHAT was happening. What I don't understand is WHY it is happening? Does the front axle move that far from side-to-side (on level ground, there's almost six inches of clearance between the drive shaft and the skid plate)???

 

[nickangus]

track bar tight thats the only thing i can think of it being

my got really lose- when i turned the wheel the front end would move from side to side over the axle
also got a really be death wobble on the freeway

im running a rustys 6.5" lift

-nice front ARB

 

[badbowtie87]

I really dont see how the axle could travel enough to hit your belly pan. Also if it were comlpetly flexed out wouldnt it move in the opossite direction of the belly pan due to track bar?? Unless the track bar bracket has come loose but im sure you would have noticed that immediatly.

 

[HaleYes]

Flex it out and look?

 

[corbinafly]

Under compression your front axle will move to the right. Especially when compressing the passenger's side.

Kyung

 

[Goatman]

You pretty much have to take a look at it flexed to see what to fix. Obviously the pinion is rotating up and the angle of flex is putting the yoke into the pan. The fix is probably to adjust you control arms some so the pinion doesn't rotate as much.

I'd also check your tranny mount. You might not even be hearing the yoke hitting, you might be hearing a thump from the t-case smacking the mount if the rubber is completly torn.

 

[canadian-xj]

Maybe check your engine mounts as well?

 

[MIXJ]

angle grinder to the skid plate. Easiest thing to do. Use a cutting wheel and make a little notch where the driveshaft is making the marks on the skid.

 

[cwlongshot]

Its unlikely its your DS that is contacting you skid. It just dosent move that far sid to side. My first answer was its your Track bar as prev suggested. Mine loosens up about once a year and makes a popping sound to let me know its time to tighten!!

Flexing it out and looking is a GREAT way to prove this to your self that its just not hitting. If by some streach it is hitting...you have major front end problems. That again will begin with that track bar!!

Good luck,.
CW

 

[meatplow5150]

Its unlikely its your DS that is contacting you skid. It just dosent move that far sid to side. My first answer was its your Track bar as prev suggested. Mine loosens up about once a year and makes a popping sound to let me know its time to tighten!!

Flexing it out and looking is a GREAT way to prove this to your self that its just not hitting. If by some streach it is hitting...you have major front end problems. That again will begin with that track bar!!

Good luck,.
CW

I agree that it has to be a problem with the track bar, but it's not loose. I tightened everything before wheeling it on Sunday... as far as flexing it out, I have done that already. I got it twisted-up in some ruts and did not experience the problem.... never heard it on level ground or while going downhill, only on steep, bumpy climbs. I had been thinking that maybe the TC chain was slipping, but I put it under a good bit of torque on some rocks as well and that didn't reproduce the noise. All of the evidence that I have points to the DS impacting the skid plate, unlikely as it may seem.
I have a crossover steering setup in mind and will likely go to an OATB using heims instead of the rubber bushings. Maybe the additional rigidity of a heavier TB using heim joints will fix the problem...

 

[Goatman]

It most certainly is possible for the driveshaft to be hitting the skid plate, and it would have nothing to do with the track bar. The track bar would have to be pretty damn loose and very noticeable for that to be the cause. On one suspension setup that I had the pinion yoke would hit the upper control arm hard enough to break the tab on the yoke that holds the u-joint cap in, and it never made any noise. You're breaking the zerk fitting off the shaft, so it's hitting something, though the zerk could have broken off against a rock.

Since the noise you have is under a load, it's likely either the t-case chain, which would make a loud pop and would also do it if you turned sharp with a wheel trying to climb a big rock, or it could be a bad tranny mount and the torque is causing the t-case to thump against the mount or even the bottom of the floor.

 

[anderld47]

Hood up, put it in drive (engine running), step hard on the brake, give it some sharp hits on the gas pedal, and have someone watch to see if your engine is rocking around. If it is, it's probably your motor mounts.

 

[woody]

The "recently installed" engine / trans skid is a likely culprit... not so much the skid, but the front brace for it.

If after a close inspection doesnt point anything out (look for shiny metal where it shouldn't be) I'd wipe all the funk off the suspect areas, and apply something of a contrasting color (white-out fluid, nail polish, paint-pen etc) aand then repeat the problem. Areas where the applied "tell-tale" is worn off... are your problem areas. make clearance with a grinder or limit your travel in that direction.

To "hip-shoot" it... Rusty's engine & tranny skid has a front brace that looks like a laid-over "P" - without the extended line - that spans across between, and attaches by the LCA bolts. I have heard that they sometimes get with the driveshaft under front compression... and that grinding a radius along the leading edge of the brace is a cure.

 

[meatplow5150]

Well, I apparently can't "eyball" distances very well when I'm laying under the Jeep

. After getting back under it with a tape measure instead of a camera, the clearance between the DS and the skid plate is actually only about 1.25" at the slip joint and 1.5" at the widest part of the pinion yoke. Clearly the problem is sideways movement of the axle under suspension compression as well as compression of the crappy rubber bushings. Compounding the issue, the axle is about 1/4" too far over to the passenger side, currently uncorrectable because the upper joint is screwed as far into the track bar as it will go (TB not threaded far enough into the tube/stud on mount too long).
So now I have my work cut-out for me. Thanks for all of the input!

 

[fdsa487]

It seems like you found the problem, but I have one thing to say. I had this same sound going on before. I could not figure out what it was. A popping noise coming from the front end somewhere in 4x AND only when climbing. I could not figure it out for the life of me. I took it to a shop and they said my front drive shaft needed to be rebuilt...

They rebuilt it and I have not heard the noice once to this day and its been awhile and has seen a good amount of wheeling.

 

[cwlongshot]

Well, I apparently can't "eyball" distances very well when I'm laying under the Jeep

. After getting back under it with a tape measure instead of a camera, the clearance between the DS and the skid plate is actually only about 1.25" at the slip joint and 1.5" at the widest part of the pinion yoke. Clearly the problem is sideways movement of the axle under suspension compression as well as compression of the crappy rubber bushings. Compounding the issue, the axle is about 1/4" too far over to the passenger side, currently uncorrectable because the upper joint is screwed as far into the track bar as it will go (TB not threaded far enough into the tube/stud on mount too long).
So now I have my work cut-out for me. Thanks for all of the input!

As you understand, this measurement changes things....1.5" is worlds different then 6" so I agree, its could easily be what you have found. Good job!! Hope the fix isnt too horrible.

I will stand for my prev comments, if you have contact and the parts where 6" away you had FAR greater problems and the track bar and motor mounts would have been my first place to look.

CW

 

[Goatman]

Well, I apparently can't "eyball" distances very well when I'm laying under the Jeep

. After getting back under it with a tape measure instead of a camera, the clearance between the DS and the skid plate is actually only about 1.25" at the slip joint and 1.5" at the widest part of the pinion yoke. Clearly the problem is sideways movement of the axle under suspension compression as well as compression of the crappy rubber bushings. Compounding the issue, the axle is about 1/4" too far over to the passenger side, currently uncorrectable because the upper joint is screwed as far into the track bar as it will go (TB not threaded far enough into the tube/stud on mount too long).
So now I have my work cut-out for me. Thanks for all of the input!

You can drill a new hole for the track bar axle mount and give yourself some more adjustment to move the axle a little to the passenger side.......very simple to do.

 

[Rocketman]

Make sure you still check that driver side engine mount...

BETCHA!

 

[meatplow5150]

You can drill a new hole for the track bar axle mount and give yourself some more adjustment to move the axle a little to the passenger side.......very simple to do.

Yeah, I thought about that when I installed the "H/D" track bar mount, unfortunately, the axle is too far to the PS already and there's not enough room to cleanly make another set of holes to move it to the DS.

 

[meatplow5150]

Hood up, put it in drive (engine running), step hard on the brake, give it some sharp hits on the gas pedal, and have someone watch to see if your engine is rocking around. If it is, it's probably your motor mounts.

Ok, so I took your advice on this, and not surprisingly, under a little bit of torque, the enging doesn't move... gas it a little more and the DS of the engine "jumps" up about 1 - 2 inches (measured, not eyeballed), accompanied by a popping sound. Soooo.... I guess I'll be replacing engine mounts too now. Now my question is, does anyone have recommendations on what brand to use? Are there any that "significantly" improve over the OEM mounts? Any advice would be greatly appreciated!