Hey guys new to the forum and got an issue. I have an 02 wrangler with the 4.0, nv3550, and the np231 t case. I keep hearing this odd noise almost sounds like the knobby tires tapping against the fender flares bit it's coming from under the jeep. I just redid the whole motor, rebuilt the t case with a sye, Novak shift cable new TW driveshafts ect. Only makes the noise when in first and second gear after I get moving then usually goes away but it doesn't happen all the time I was thinking maybe i screwed up and didn't put enough fluid in either the t case or the trans kind of has me squirreled right out any insight would be greatly appreciated
Odd knocking noise from underneath
- Thread starter Tjguy1994
- Start date
Welcome. Did you fill the t-case and trans on a level surface until it ran back out the fill hole(s)? Not a lot of info to go off of, but if it does the knocking on take off only, my first guess would normally be that something is loose and able rock back and forth when torque is applied (like a motor mount, tranny mount, suspension or steering part not torqued down properly, worn bushing etc.).
Also, have you hit all your zerk fittings with grease in a while? If not, wouldn't hurt to do that now and see if it helps with any metal on metal contact that could be making noise.
If you can grab a video/sound recording of the noise as you are driving, perhaps that will help the folks here to help diagnose. Somehow you need to try and narrow down the area from where the noise is coming from (and how it feels if a vibration is felt could also help to narrow it down). I know this can be really tricky. Sometimes you can also mount a GoPro underneath at several different angles and look for movement in the area you suspect. If you can reproduce it going slowly, you could also have a someone try to look at it from outside the Jeep when you are taking off from a stop. Even if they can't see anything, they could possibly help narrow down the general location of the noise since it should be louder outside the Jeep.
Also, have you hit all your zerk fittings with grease in a while? If not, wouldn't hurt to do that now and see if it helps with any metal on metal contact that could be making noise.
If you can grab a video/sound recording of the noise as you are driving, perhaps that will help the folks here to help diagnose. Somehow you need to try and narrow down the area from where the noise is coming from (and how it feels if a vibration is felt could also help to narrow it down). I know this can be really tricky. Sometimes you can also mount a GoPro underneath at several different angles and look for movement in the area you suspect. If you can reproduce it going slowly, you could also have a someone try to look at it from outside the Jeep when you are taking off from a stop. Even if they can't see anything, they could possibly help narrow down the general location of the noise since it should be louder outside the Jeep.
I'll try to get a video at some point tonight. Pretty much I just gutted this whole thing and redid the entire drivetrain. Didn't even think about the motor mounts or any of that so I will have to check but oddly enough I went for a ride last night and didn't make the noise until I switched between 4hi and 2 high trying to diagnose the problem. Before I got it out of my garage I went back over the suspension parts and greased the s@#% out of them but at any rate I am going to get it up on Jack stands tonight put it in gear and let everything roll while it's up on the stands and try to get the video up of the noise
Cool, sounds good! The t-case linkage is an abomination on the TJ. Many replace the over-engineered piece of junk with the Savvy cable. That's what I am going to do if mine starts acting up again. It can rattle, knock, and make noise, so perhaps try pushing down on it or pulling up on it a bit to see if the noise stops when doing so.
Well gentleman me and my brother diagnosed that it is indeed coming from the transfer case only when the wheels are turned to the right in 4 hi. Going to dive into it and hopefully let you guys know what is broken. Hoping it's something simple
The transfer case makes noises when you turn the wheels to the right in 4hi? But you said it made the noise when driving, are you driving in 4hi? In any case I am not an expert but I don’t see how the transfer case would act any different based on which way the wheels are turned while it’s not in motion at least.
It was making the noise while I was driving in 2 hi then I got all four wheels off the ground and on jacks stands and the noise was more pronounced while in 4 high currently at work so when I get out I have a buddy of mine coming over to rip the t case apart then we will see also I rebuilt the whole thing case so there is a strong possibility that I messed something up while I was in there but hopefully I will find out tonight what the deal is and let you guys know
Well figured it out. Noise is coming from the throw out bearing/ clutch even though it's a brand new centerforce. Not the first time I have had issues with them. Does anyone know of a more reputable company if there even is one?
i have a similar issue. mine is making the sound only when i hit the accelerator. when i left off it stops. got under it thinking maybe a u joint but no signs of that. upon further inspection i found my rear left upper control has ripped off the frame. the guy before me didn't put adjustable control arms on it. i was hoping to them on my own time. i think this is a separate issue and not the cause of my knocking sound seeing as how it only happens when throttle is applied. i attached pictures of the control arm.
liquidfluidity
TJ Enthusiast
OP - sounds like all of the issues that my bad tranny mount had. The rubber had torn and would rattle under initial load.
Jon Wildes - nice broken bracket. it looks to have shifted quite a bit....
Jon Wildes - nice broken bracket. it looks to have shifted quite a bit....