242HD heavy clunk/thump over speed bumps - JeepForum.com
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post #1 of 18 Old 01-23-2021, 12:23 PM Thread Starter
DoctorTim
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Every time the rear end compresses over things like speed bumps and gutters in the road I can hear and feel a heavy thump/clunk in the center of the jeep.
All suspension parts are new and bolts re-tightened. Shocks new. U-joints new. Steering and axle parts checked.

Anyone ever experience this? It seems like every time the slip yoke compresses/extends I get a clunk. I've greased the slip yoke, no change.
Today I'll remove the rear driveshaft, cap the hole, and drive over a speed bump in FWD to see if it does it. Ill post the update.

Update: drove without the rear driveshaft, tc rear out capped, and 4hi. No thump at all. Definetly TC slip yoke related somehow.

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post #2 of 18 Old 01-23-2021, 01:14 PM
snowbuggy
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I always blame the rear ball joint for clunking in the rear. I have a couple doing it and I plan to change the ball joints in a couple weeks.
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post #3 of 18 Old 01-23-2021, 01:31 PM Thread Starter
DoctorTim
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Quote:
Originally Posted by snowbuggy View Post
I always blame the rear ball joint for clunking in the rear. I have a couple doing it and I plan to change the ball joints in a couple weeks.

I've replaced the rear arms with the IRO kit. No longer have a ball joint back there. But yeah that would have been my first thing to check as I have experienced that before. Note that this thud/clunk is much more pronounced than when a rear ball joint knocks.
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post #4 of 18 Old 01-23-2021, 05:39 PM Thread Starter
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Just drove it without the rear driveshaft and the rear output capped. It definetly has something to do with the rear slip yoke / transfer case / driveshaft because it doesnt do it anymore.
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post #5 of 18 Old 01-24-2021, 06:06 AM
snowbuggy
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I guess you are getting closer. Did you have to change the driveshaft when you lifted it? It does sound like the slip yoke if it's too long or too short.
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post #6 of 18 Old 01-25-2021, 12:27 PM
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Yeah, it sounds as though the shaft is to long, and bottoming out? Weird though, didnt you use the rear driveline that came with your transfer case?

'00LMTD-4.7l,242hd,D30,D44A,3.73's,True-trac front,Spartan rear,4" short arm lift,JK'sW/32's
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post #7 of 18 Old 08-05-2021, 08:24 PM Thread Starter
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Update. Still having this issue and seems to be getting worse. Problem goes away with the rear ds removed. Getting concerned its gonna cause some more serious damage if i let it continue. Planning to replace the output bearing with a tight tolerance bearing to see if that helps or changes anything. Asking for a friend.
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post #8 of 18 Old 08-08-2021, 07:42 AM
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I get a thump/clunk in mine when i first back out of the driveway.(sounds like someone smacking the floor under the front seats-just one time) Nearly every time, but almost never get any noises going over speed bumps or trail riding. Its enough to make me notice, but never made me wanna tear into the Jeep to find it. I recently found that my initial 242HD swap had a stretched chain. It would grind badly in 4low on steep climbs. I swapped out that 242 for another, and stopped my other noises and general looseness in the drivetrain, but the thump is still there. I was hoping it was going to be fixed, but no go... I have new motor and trans mounts, and new bushings/balljoint in the rear upper control arm. Rear Lower control arms are tight and the bushings in good shape. Front upper control arms are new Core 4x4 adjustables, and the front lower control arms are upgraded with the lift with offset brackets at the frame. Im about to think its something to do with the exhaust. Mine HAD a 3" catback exhaust installed with a flowmaster muffler until I folded the T-pipe into a pretzel the other day while trying to navigate a steep rock wall. I had to cut the t-pipe off to get the engine to breath, and so far I have just added a short downturn tip to the back of the muffler to blow the hot air on the ground in front of the rear axle. I havent driven it much since i did this, but I dont remember it thumping the last time I drove it. And I do remember seeing a shiny spot on the top of the t-pipe where it went over the rear axle( it was just Kissing the floor) when i cut it off....Are you positive it isnt the exhaust hitting something? There is only one hanger after the trans mount. And its clear in the back next to the fuel tank...I know this doesnt jive with your removing the rear driveline, but just brainstorming here...

'00LMTD-4.7l,242hd,D30,D44A,3.73's,True-trac front,Spartan rear,4" short arm lift,JK'sW/32's
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post #9 of 18 Old 08-09-2021, 12:03 AM
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Quote:
Originally Posted by DoctorTim View Post
Every time the rear end compresses over things like speed bumps and gutters in the road I can hear and feel a heavy thump/clunk in the center of the jeep.
All suspension parts are new and bolts re-tightened. Shocks new. U-joints new. Steering and axle parts checked.

Anyone ever experience this? It seems like every time the slip yoke compresses/extends I get a clunk. I've greased the slip yoke, no change.
Today I'll remove the rear driveshaft, cap the hole, and drive over a speed bump in FWD to see if it does it. Ill post the update.

Update: drove without the rear driveshaft, tc rear out capped, and 4hi. No thump at all. Definetly TC slip yoke related somehow.
Try lowering your tyre pressures.
We run 30psi in our lightly loaded 4.7 to reduce the thump over speed bumps.

We also get a quieter more comfortable ride, along with better road holding and steering at 30psi.
If I dropped the rear pressures a bit more, I'd get better road holding and steering.
But our insurers might not like it is they found out.
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post #10 of 18 Old 08-10-2021, 06:51 AM
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I used to get a noise in a similar fashion going over speed humps and braking - tracked it down to the insulation above the exhaust. It's a kind of aluminium sandwich affair and from what I can make out, due to vibrations it work hardens around the securing studs, then the holes open up and it moves around as you brake, accelerate and the like. Doesn't explain why it would stop with the rear driveshaft off, unless it was hitting the driveshaft?

I was getting a banging noise the other day and this was a broken clamp on the rear sway bar allowing the bar to move.

I have also just greased the slip yoke and the noise I was getting on braking has now disappeared. I used CV joint grease to do this.
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post #11 of 18 Old 08-10-2021, 02:32 PM
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check your driveshaft u-joints.

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post #12 of 18 Old 08-17-2021, 10:31 PM Thread Starter
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DS u-joints are all new. Suspension is all new. Torque of everything was checked. I looked around of signs of metal-on-metal contact... I'll be installing a tight-tolerance bearing on the output soon to see if the axial play in the output bearing might be causing this.
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post #13 of 18 Old 08-18-2021, 02:45 AM
Delta0
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How about you get a used rear driveshaft from a scrappers?

Then check the length of your shaft against the other shaft?

If the scrappers shaft is shorted than yours, use it.

If the scrappers shaft is the same length, cut say an 1/8th inch of the front end, and try it?
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post #14 of 18 Old 10-08-2021, 11:35 AM Thread Starter
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Problem solved with the following method for future reference in case anyone else has this issue. The cause of my issue was too much axial play between the tailcone, bearing, and snap ring. When the suspension compresses, the driveshaft pushes/pulls on the splined output shaft.

Replaced the rear output bearing with a tight-tolerance one from mcmaster (PN 6661K48).

Replaced the output snap ring with a shaft collar (PN 6063K23). I made sure the shaft collar was installed tight up against the bearing.

Sanded down the tailcone housing mount face so the bearing is more tightly clamped. I did this by spray gluing 240 grit sandpaper on my welding table and sanded it down by hand. Time consuming but the finish is nice and flat. You can test the depth by marking the outer bearing race and tailcone mount face with sharpie, slide the tailcone over (no bolts), and rotate it around. The areas where the tailcone contacts will wear away. I did this until the mount face barely touched and the bearing race had full contact.
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post #15 of 18 Old 10-08-2021, 11:48 AM
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Interesting, I was going to say adjust your lower arms and upper IRO A-arm out to move the axle backwards if it was bottoming out at the slip yoke.

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