Unknown Issue: Knocking coming from under TJ when decelerating - JeepForum.com
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post #1 of 19 Old 04-02-2019, 09:05 PM Thread Starter
Eric6123
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Unknown Issue: Knocking coming from under TJ when decelerating

Not sure of the type of response I'll get here, but I am starting to feel all out of options. I recently purchased an 05 TJ with 52k miles on it for 11k. There were some issues, mainly the oil leak underneath (totally normal for a jeep this age) I have an issue with the speedometer sticking, no rear bumper, dana 35 in the rear, and a dash that rattles REALLY bad. I know, I know, I'm probably a moron and got ripped off.

That said, I took my jeep in and got a 3' JKS Jspec lift with 33 tires. As soon as I drove my truck off away from the garage, I have a knocking coming from the rear end. My mechanic had assured me that the issue was with my lower control arms that needed to be replaced. So, I spent another 1100 putting in control arms and I installed some fenders as well. The knock has not been fixed, if anything, its more extreme. Turns out my mechanic is kind of a jerk and said he's stumped and I am making to big of a deal out of it.

I took it to another mechanic today, that said the pinion angle was off, and that might fix it. I paid him $115 to adjust the pinion, knock still isn't gone. He then pointed out that when my lift was installed, the mechanic neglected to out in my linkage adjustment, and that could be it. That was not it. Now the mechanic wants to service my rear diff because it needs it anyway, which will be an additional $200, and no guarantee it could be that either. He said after that he would move to the transfer case and the transmission, still no guarantees of finding the issue.

So, it appears I have a mystery issue. I am already 18k-19k deep in this thing, and feel awful. The AC just went out adding insult to injury, another 1200 to fix. If it is the axle I am going to essentially have a 30k jeep 05 jeep with no AC and a rattling dash. The issue happens at lower speeds once I let off the gas and is a knocking noise coming from under the jeep.

Has anyone experienced anything like this issue? Is this thing worth putting more money into, or should get what I can for it and cut my losses? This is my first mod and its starting to make me feel sick. Any help would be much appreciated.

TL,DR Brought my jeep in for a lift, now has a knock at speeds under 35mph when decelerating. currently 18k in. What should I do?

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post #2 of 19 Old 04-02-2019, 09:21 PM
biffgnar
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Need to try to start eliminating driveline components. Step one remove front driveshaft. Drive and see if any change. Step two put front driveshaft back, remove rear driveshaft, put jeep in 4H, drive and see if any change. Step three remove rear diff cover and see what oil looks like and condition of gears. Posting a photo of pinion angle would also be interesting.

After driveline components I'd start checking torque on everything that was touched in lift install - control arms, trackbars, etc. If it happened right after lift install highly likely something that was touched during install or affected by the lift (e.g. driveshaft angle). While not impossible the chance that another problem popped up coincidentally with transmission or TC is unlikely.

On a bigger picture issue if you want to own an 05 TJ might want to invest in some tools and an FSM. If you keep taking it to shop for everything it has the potential to get old and expensive. Where do you live? Finding local jeep club will help connect you with other jeep owners who can help.
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post #3 of 19 Old 04-02-2019, 09:24 PM
JEK3
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Start simple (do this yourself). Get underneath and look around. Pay particular attention to the exhaust, look at the mounts (especially the one within the skid underneath) and the clearance around it - it can move a good 1/2" to 1" on acceleration and deceleration. Also look at the transmission and transfer case, and the mount underneath - again, it moves. I don't know what comes with the lift you got, but most lifts change the driveline angles, which can cause parts to start hitting each other under certain circumstances.
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post #4 of 19 Old 04-02-2019, 10:15 PM Thread Starter
Eric6123
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Hi and thank you for the response. I live in Denver CO. I don't have my own tools, but my brother does and we could work on it at his house. I just had the pinion angle adjusted, and that wasn't the issue.

I've read that it can sometimes be the brakes, do you think that is a possibility? Also, I might sell or trade in and start over. Did I overpay for this thing at 11k. It has 52k miles on it.
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post #5 of 19 Old 04-02-2019, 10:19 PM Thread Starter
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Hello and thank you for responding. I should mention that the knocking is correlated to the circulation of the wheel, so it should be anything loose or with the suspension. I've had the suspension looked at twice, and both times it was said to be kosher. Yes, the issue happened immediately after I got my truck back. It knocks in correlation with the wheel circulation.

Also, did I overpay for this thing? When I bought it, only issue was the cluster and lower control arms. Its had 52k miles on it. I might want to start over and want to educate myself on the proper price. What should one pay for an '05 Wrangler with 52k miles?
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post #6 of 19 Old 04-03-2019, 05:50 AM
biffgnar
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Someone saying the pinion angle is correct and us seeing that are two different things. There are two different ways to set the pinion depending on what rear driveshaft you have. One possibility is that you have the OEM shaft and with the lift you are on the edge of working limit of that and need to change to a double cardan driveshaft. Removing shafts and test driving as described above would help diagnose that.

Brakes can cause problems but this doesn't really sound like that. Also brakes probably would not have been touched when doing lift so less likely.

Correlation with wheels spinning brings me back to checking the driveline, as it turns along with the wheels.

On the surface the price you paid while not a steal doesn't seem awful for a well cared for non-rusty jeep. People do tend to overpay for low miles though. With this vehicle and engine, maintenance is way more important. I'd take my 06 with 167k everyday of the week before a poorly maintained one with 52k on it. Realistically though it is an almost 15 year old vehicle and there will be things wearing. Taking it to shops who are just guessing and throwing parts at it will get expensive.

If you want to fix this you need to take a deep breath, stop with random guessing and walk through a real diagnosis. We can help with that but you need to actually follow the steps suggested. You can't count on shops having done everything correct. They likely did not or you would not have this issue.
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post #7 of 19 Old 04-03-2019, 05:54 AM
ZEN357
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Quote:
Originally Posted by Eric6123 View Post
Not sure of the type of response I'll get here, but I am starting to feel all out of options. I recently purchased an 05 TJ with 52k miles on it for 11k. There were some issues, mainly the oil leak underneath (totally normal for a jeep this age) I have an issue with the speedometer sticking, no rear bumper, dana 35 in the rear, and a dash that rattles REALLY bad. I know, I know, I'm probably a moron and got ripped off.

That said, I took my jeep in and got a 3' JKS Jspec lift with 33 tires. As soon as I drove my truck off away from the garage, I have a knocking coming from the rear end. My mechanic had assured me that the issue was with my lower control arms that needed to be replaced. So, I spent another 1100 putting in control arms and I installed some fenders as well. The knock has not been fixed, if anything, its more extreme. Turns out my mechanic is kind of a jerk and said he's stumped and I am making to big of a deal out of it.

I took it to another mechanic today, that said the pinion angle was off, and that might fix it. I paid him $115 to adjust the pinion, knock still isn't gone. He then pointed out that when my lift was installed, the mechanic neglected to out in my linkage adjustment, and that could be it. That was not it. Now the mechanic wants to service my rear diff because it needs it anyway, which will be an additional $200, and no guarantee it could be that either. He said after that he would move to the transfer case and the transmission, still no guarantees of finding the issue.

So, it appears I have a mystery issue. I am already 18k-19k deep in this thing, and feel awful. The AC just went out adding insult to injury, another 1200 to fix. If it is the axle I am going to essentially have a 30k jeep 05 jeep with no AC and a rattling dash. The issue happens at lower speeds once I let off the gas and is a knocking noise coming from under the jeep.

Has anyone experienced anything like this issue? Is this thing worth putting more money into, or should get what I can for it and cut my losses? This is my first mod and its starting to make me feel sick. Any help would be much appreciated.

TL,DR Brought my jeep in for a lift, now has a knock at speeds under 35mph when decelerating. currently 18k in. What should I do?
Had a similar thing happen to me, knocking for two days, then it went away, came back for 20 minutes, went away and has never came back. Not sure what it was, but my mechanic couldn't find anything wrong.
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post #8 of 19 Old 04-03-2019, 06:27 AM
gutthans
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Biffgnar is correct. Follow his diagnostic plan to narrow down where the issue is coming from. Post pictures if you want us to help 'guess'.

It is often the case that problems occurring immediately after an equipment change are related to or caused by, the change. Typically, shops simply do what you asked. They don't go beyond that unless the installation is inhibited by something that HAS to be done. You wouldn't be the first person to get 'secondary' issue related to installed equipment that a good Jeep shop would have advised you about as a courtesy.

IF you insist on modifying your Jeep you need to learn how she works...Same with marrying your girlfriend.
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post #9 of 19 Old 04-03-2019, 06:33 AM
GermanyChris
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When I had this problem one of my rear trackbar bolts had come loose

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I'm generally a very pragmatic person: that which works, works. -- Linus Torvalds
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post #10 of 19 Old 04-03-2019, 09:38 AM Thread Starter
Eric6123
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Thank you for all of the responses here. I will heed the advice here and pull it from the shop. I will also post the requested pictures and start moving through it piece by piece. I have VERY little mechanical knowledge, but I would agree that If I am going to be modding I need to learn how to work on it.

Thanks again from everyone who has been working with me. I am headed out of town tomorrow, but will be back on this thread next Thursday. Anyone that would continue to help would be very much appreciated.

Thanks again, everyone!
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post #11 of 19 Old 04-04-2019, 07:48 AM
Goatman#1
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U-joints can do this exact thing. When you un-load the engine the axle will rotate back down, changing the pinion angle. And with no load on the u-joint it is free to have the cross rattle around in the bearing caps. Check and grease all the u-joints and driveshaft slip joints (same thing can happen here too) can be the slip joint to the transfer output too. This exact thing is how I know the PTO drivetrain in our hay baler is due for a rebuild.
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post #12 of 19 Old 04-04-2019, 11:58 AM
Wheelin98TJ
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Pinion angle is probably off.
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post #13 of 19 Old 04-12-2019, 07:17 PM Thread Starter
Eric6123
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Hey Everyone, here is a link to the noise the jeep is making. Any ideas?


Last edited by Eric6123; 04-12-2019 at 07:32 PM.
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post #14 of 19 Old 04-14-2019, 01:21 PM
Goatman#1
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Boy that sure sounds like a U-joint banging around. I'd pull the driveshaft and check for slop. Do you have grease fittings in the U-bolts? If so give 'em a good 5 or 6 pumps of grease. If the sound clears mostly up then you know for sure.
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post #15 of 19 Old 04-14-2019, 02:21 PM
Strelnikov
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My 2003 Dodge Ram 2500 4WD pickup is doing the exact same thing. Except mine is only doing it when the truck is going in a straight line. When I make a left or right turn the knocking sound stops. I'm thinking it has to be the front u-joints.

Several years ago the front u-joints went bad on my '99 TJ Sahara. They didn't make any knocking noise but the mechanic that told me they were bad grabbed the shaft behind the u-joint and wiggled it back and forth. There was a knocking sound when he did this and I could see that they were loose. It looked like there was nothing left of the bearings inside the u-joints.

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'99 TJ 4.0 Sahara (son's Jeep)
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