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Knock/clunk while accelerating from rear drive shaft

25K views 23 replies 12 participants last post by  Vici0usX 
#1 ·
I recently put a 6.5 bds long arm kit on my 2003 Rubicon. Obviously I had to get a new rear cv drive shaft. After about a week of use I noticed a knock/clunk noise coming from underneath my vehicle. The only time I hear the sound is when I'm accelerating, not when I'm driving a constant speed or while I'm decelerating. To track its location I disconnected the front drive shaft and drove it, still had the noise. Then dropped the rear drive shaft and drove it and no knock. Reconnected the rear drive shaft and the noise returned. The rear drive shaft has only a 300 miles on it and spicer u joints. When I grab hold of the cv joint and try and move it, it wiggles a little and sounds a little like the sound I hear. I thought it was my pinion angle at first, thought it was too high after my first adjustment, then I dropped it a bit, a few degrees below inline with the output shaft of the transfer case. I noticed on the OEM drive shaft has a sort of spring load pushing it back out as it compresses and decompresses as the rear end moves. My new drive shaft does not have that spring load feel to it, but it does have a grease fitting on the side and when I pump grease into it it comes out a little hole at the bottom. Two thoughts, its just there to lube the drive shaft, two there might suppose to be a plug at the bottom to keep pressure but it is missing. I can't figure it out and it's driving me up the wall. I've searched the forum up and down and cant' seem to find anything. I would kiss the person who helps me resolve this, don't let that scare you I really won't lol, just please help.
 
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#2 ·
Assuming the rear axle and drive shaft are okay, some things you could check are, the rear shocks, they can hit the lower coil cups after a lift without shock mount extenders, also shock bushings can slip to one side of the bar pin mounts, check the exhaust system, grab it in various areas and shake it hard side to side, the up and down, to see if it's hitting anywhere, check the transmission and motor mounts which could allow the drive train to shift when accelerating if one fails. Hopefully you inspected the trans mount for wear while installing the long arm kit.
 
#3 ·
My long arm kit came with rear shock mount extenders and also came with new transmission mount. The knocking noise increases in speed as I accelerate. I think if it was a motor mount it wouldn't continue to speed up as I increased speed. It would speed up and slow down with the rpm's of the motor. I think it may be the drive shaft because when I removed the rear drive shaft the knocking stopped. The rear drive shaft CV joint has a little wiggle in it, not a lot maybe an 1/8 of a inch or so, but I'm not sure if its suppose to be there, its a brand new shaft.
 
#5 ·
A noise Increasing in speed may rule out stuff like exhaust and shocks hitting. A good new drive shaft should not have any play at all, is the play actually the shaft or is it coming from movement at the pinion yoke or transfer case ends? If the shaft is not the issue it might be a good idea check pinion shaft for play, and to pull the diff cover and inspect your gears, check the ring and pinion teeth, ring gear bolts, pinion shaft bearings etc. I have seen pinion yoke nuts & ring gear bolts come loose. If the noise is only under load it could be a bearing. Also the Rubicon OEM Air lockers have been prone to various failures. Can you try a different drive shaft to rule that out?
 
#6 ·
mine did this a few months ago. Like a week after I got my tj I got stuck the next day or two days later I forget which it started clonking when I got on the gas. I took it to the local shop and they said there was nothing wrong but mud caked everywhere. The guy said he knocked it all out and it went away. Never to happen again.
 
#7 ·
I don't have another drive shaft to swap out, I have the original but I'm pretty sure it would cause serious vibrations because of the 6.5in of lift. I have checked the pinion shaft for play at the diff and the transfer case. When I took the rear drive shaft out and drove it down the road in 4wheel drive the knock was gone. If the drive shaft was off would you be able to tell if the bearings are bad and wouldn't the knock continue if there was damage to my ring and pinion while the drive shaft was off? And I wanted to point out it only makes the noise during acceleration. If I take the diff cover off to check the ring and pinion teeth, how do I diagnose bad bearings and check the lockers. The rear diff will lock and unlock when I turn the lockers on and off. I haven't locked them and tried to see if it still makes the noise, not sure if that will help find the problem but I'll find out and get back to you. Thanks for your help.
 
#9 ·
Clunk in rear upon acceleration

I would love to get to the bottom of this.

I have the same noise in my '06 LJ Rubicon, 3.5" short arm with 1.25" BL, adjustable uppers front and rear. It is almost reproducible when accelerating in first from idle. Sometimes you can hear it when letting off the gas only in first, high RPM's. With several speed bumps in my neighborhood I hear it very often and it's driving me up a wall.

So far I have checked engine and tranny mounts, flipped rear shocks, tightened exhaust mounts, and found no loose parts floating around in back :)

It does not occur when turning, which made me think it was the control arm bushings - especially after I read a post about RE bushings failing. I have poly at frame and SF at axle. Tightening to spec did nothing for the noise.

Under no load the rear driveshaft has some play and I have heard conflicting information about how much backlash should exist in a driveshaft under zero load. Some say a slight turn and others say none at all. If I rotate the rear shaft under no load it makes a strikingly similar sound. Could it be internal to the tranny or TC? A chain that needs adjustment? Rear-end? Hard to believe the issue would be internal on a daily driver with under 40K.

I have yet take off my rear shaft and test only front but, after reading the OP, may check this soon. I am willing to bet the noise doesn't occur as there will be no rotational torque to the rear.

Any comments/questions provided would be greatly appreciated.
 
#10 ·
I have the same issue. I've had my new cv driveshaft on for only 3 days. Its already driving me crazy. before I put both shafts back on I ran through 2 4 and 4lo to make sure everything shifted right and no noise coming from xfer case. It feels like every time the shaft spins around it clicks. It doesn't change based on rpm just speed. At the same time I replaced the stock steering stabilizer. I was driving down my road and got the death wobble. This made the whole jeep shake and it seemed like a lot of it was coming from driveshaft. Don't know but scared the sh** out of me. I notice little grease spots all over the underside of my jeep looks to be coming from ujoints.

Thoughts??
 
#11 ·
I don't know about your death wobble but I had the constant, and increasingly louder, clicking from my new rear DS and it turned out the pinion angle was off causing the center ball to bind. Had a new one overnighted from Tom Wood and it's been good ever since (with proper pinion angle!). Just getting it balanced now.
 
#16 ·
Hey guys, I know this sound all too well. I went to the (previous owners) shop that did the rear end (new axels and all) 2k miles ago and they SAID they pulled the cover and found nothing wrong, happily suggesting it was my Xcase and that they would do it for a nice $1000. Frustrated, I pulled my transfer case, split it, completely rebuilt it (finding nothing wrong). Next on the list.. throw-out bearing, I went to a tranny guy and he showed me it was too much backlash in the rear end. Went back to the SAME gear shop with a different attitude and all of a sudden they broke down and said, yea we'll take another look. 4 hours later, They found broken axels. I got 2 new OEM free axels and the rear end completely rebuilt for FREE. The knocking is significantly reduced but this gear shop isn't a great shop at all so I still think there is a small amount of backlash in the rear end that they couldn't shim right. Oh well, another reason to go to the 44 when i take it to an actual "4wheel" shop. Hope this helps, never trust the mechanic
 
#17 ·
Having a simliar issue which seemed to happen right after I got a replacement rear axle. If I get under my jeep, I can move the rear driveshaft back and fourth (i'm not talking about spinning it) There is some space inbetween the ujoint head and where it connects to the rear axle. Is this normal? I dont recall any play before.

Axle is used, the ujoint is brand new. I even tried taking the unjoint off and putting a newer one on, there is still play when I install the rear driveshaft. Almost makes me think that axle/driveshaft connection (the piece that connections the driveshaft to the rear axle) is bent outwards? Is this common?

Is there supposed to be any play in the rear driveshaft?
 
#18 ·
That play is normal, as far as I have been told. It is called backlash and every driveshaft/axle should have some for normal operation. Some gearheads even claim a 1/4 turn can be made. On my Rubi I can turn the shaft a little, but enough that it makes a small clunk at either end. As far as the space between the u-joint and rear yoke, I am afraid a picture will be necessary to determine what you're describing.
 
#19 ·
I had the same frustrating clunking sound from my 05 Rubicon after installing a Coast Drive Line rear CV shaft. After trying everything suspension related (I thought it was a loose control arm bolt) I then remembered reading something about this same topic on a Ford Super Duty forum. The solution posted on there was to lube the spline of the rear DS. I crawled under there and shot the spline grease fitting full of grease and the problem went away.
 
#20 ·
The Toyota folks had similar issues with the Dana driveshafts, the shaft when it compressed or moved in the splined area couldn't move as the compression had no where to relieve to thus causing the clunk. Some people drilled the area by the splines to allow the area to relieve pressure when the shaft compressed, allowing it to move and not clunk. Just a thought.

Denis
 
#22 ·
Hey JV. My uppers are fairly new, they are adjustable as well. My lower are procomp fixed control arms (weird setup I know). I got the uppers for a killer price so i bought them. You have the RE Lower/Upper? Adjustable or FIXED?

My problem started happening after I got my new axle, so it could be the control arms, but doesnt sound like it. Is there any way to test that or just replace and hope it works?
 
#23 ·
I have RE ADJ uppers and fixed lowers, SF joints at the axle and SR (poly) at the frame. I was convinced it was coming from the axle but actually found the issue with the frame-side, upper mounts. I brought a laptop in the Jeep and fed a webcam down thru the drain plug hole.

Here's the video:
You can hear the acceleration, a bang, then see the upper arm slosh back a considerable amount - this is before I replaced all bushings around. This made the clunk go away.
 
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