Knock/clunk while accelerating from rear drive shaft
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.
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.
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.
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?
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.
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.
I looked at a website about a transfer case shifter knob knocking, I don't think this is the problem because I've had my hand on transfer case shifter and the knock doesn't vibrate through it but I can feel it through my transmission shifter.
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.
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.
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.