To Jeremiah Cahill
Jun 22 at 11:18 PM
I have been searching for this issue since May and haven't found any thing.

Well first off I own a 2014 JKU with no engine or drive train mods, 39100 miles, 6 speed manual (Hill Assist Off). The problem is an intermittent bang, after initially getting the Jeep to roll (only forward in 1st gear), starting from a stop. The bang does not have a particular type of acceleration when it happens with, sometimes a gentle acceleration from a parking space or a more aggressive acceleration from a stop sign crossing a road with 50mph cross traffic. Typically in weather with temperatures above 75 degrees F, and after a driving for over 45min it typical when it happens.

But as an example beginning at stop light with one car in front, light turns green, first car begins to roll, I begin disengaging the clutch, adding gas, Jeeps moving about 5mph, clutch is fully disengaged, foot removed from clutch pedal, remains on foot on gas adding constant pressure, bang occurs when more torque from the transmission is being applied to the drive shaft and eventually the wheels to accelerate from the 5mph to the point of the first shift from first to second. I haven't really watched the tach, but feels between 900 and 1200 rpms.

Now that is just one example. Since it is intermittent it is difficult to judge if it's a driving habit, since one time it could bang on a gentle right turn accelerating to 30mph or not bang on an aggressive acceleration to 50mph. But I can say on a cool day under 75 degree day it won't do it, but a 90 degree day it's almost constant, every stop/start.

I have checked at every tire rotation for one of the caliper hanging up as well as any loose hardware with the axles, shocks, springs, u joints, and drive shafts, found nothing's loose. But when I grab the rear drive shaft and turn it by hand, there is play in it an can make the transfer case bang.

he Jeep is currently at the dealer since early Monday, they of course could not find anything, so they kept it over night with one of the service managers driving it to see if the bang will return. Not prior to bringing it to the dealer I drove it for 45mins finding every stop sign and red light I could find and only got it to do it twice. So I suspect if they can't find anything that when I pick it up that I'll do it leaving the lot.

Any ideas? Thanks for the help,

 

Do you feel it, or hear it or both? how loud is it and how strong a feeling is it?

 

Last time this happened to me I found a flashlight rolling around under the back seat.

 

LMAO!!!!!! yup!!!! We had the fuel sending unit replaced on a Chevy HHR and had a this weird sound like when you drag finger nails on textured drywall. Figuring I'd take a look and find they had left something loose back there, I found myself a nice $200 LED Streamlite.......

 

Typically when it is doing it, you can really only hear it with the windows open or top open or down. As for feeling it, you can feel it if your paying attention for it. But this is intermittent, if I drive down one of our streets here that has a ton of stops signs at just about every cross street, on a section say with 10 stops in a row. The Jeep may only do it twice and may only do it on stops #3 and #8. And when it does it is after the Jeep is rolling, clutch fully disengaged and just going from a gentle pressure on the gas to keep the Jeep rolling to a more firm pressure to accelerate with traffic. Up hill, down hill, left turns, right turns don't seem to matter either. It also only does it in forward at a low speed in first gear.

But what I am thinking, even though I can't get it to do it with the rear end jacked up is possibly a brake caliper. Because when I was testing out the "Hill Assist" feature on the Jeep, trying to get used to the feel of it. It is almost at the same point where you release the brakes, brakes still holding, release the clutch, apply the gas and the brakes release. It feels just at the same moment where the Hill Assist would release the brakes is where the bang is happening.

 

Mine is doing the same thing. Mine is a 09 auto and out of warranty. I'm subscribing, hoping to figure it out.

 

Same here. 09 manual 52,000 miles. I thought it may be related to my clutch beginning to slip.

Sent from my iPhone using JK-Forum

 

I thought I finally was on to a thread that would lead me to a clue. I get this in my 2017 manual. Seems to be getting a little more frequent. Don’t notice it when coming out of garage or driveway, only after it’s been warmed up.

come to a stop, upon go - let the clutch out to start out in first gear and within about 1-5 feet of distance... “clank”.

I can barely hear it, but I feel it. It’s subtle, but something between driveline and wheels is giving a sensation that a tooth in the differential just snapped off. Rest of driving experience is fine.

a couple of times I’ve noticed that the back body feels like it gives a little wretch before the clank. Sort of like as if I was holding the brake down while letting out the clutch. Then the axle finally gives (with a little bang or clank or pop) and body rests and wheels resume motion.

I liked the description of feeling like hill assist was still “holding on” and then suddenly giving way, but the thing is, upon letting the clutch out, the wheels begin to move. For me the clank happens about right about when I have let the clutch out about half way, after I’ve started moving a couple of feet.

weird sensation / disturbing sound, for sure.

 

I had a similar clank in the rear of my 2014 auto JK. I'm not sure which thing fixed it, but one day I replaced the brake pads and changed the rear diff fluid. After that day, the clunk is gone

 

Also try measuring the backlash in the diff, look at axle wind up from worn or failed track bar bushings, or broken bracket, rear cross member Tranny mount or rear driveshaft. One way to isolate the problem is go back where it did the noise the best and put it in 4WD then repeat. You won't hurt anything and if the noise is 'softer' or gone you know it is drivetrain suspension related. Then drive in 2WD again.