I have a 2012 JKU Sahara 6-speed manual transmission which is pretty much stock all around with 118K miles.

When accelerating/decelerating in-gear I get a little bit of jerkiness. I think I can hear muted clunking and think there is something drivetrain related that is not optimal. What areas should I look at troubleshooting and how is it best to tell what is normal for a Jeep vs worn? I have had the Jeep for 18 months and it has always done this; just caught up on the rest of my fixes with this bubbling to the top.

Thanks!

 

Look at the gear lever in say 4th gear at 30mph or so and accelerate then let off the pedal. If the gear lever moves fore/aft a bit that usually means center bearing is gone in the box. And if you have a bit of rattle that can also mean bearings. I am disappointed at a lot of gearbox manufacturers as they have had a 120 years to get it right and these NSG370s are a disappointment given they have double synchros on most of the gears. One thing you can do is change the oil to Amsoil or Penzoil but make sure you get the sychromesh blend. That quietens them down some. Don't use Mopar oil as it is about twice the price of Amsoil and not as good. 118000 miles is nearly the life of these boxes. Jerkiness is not a gearbox issue rather perhaps a miss in the engine!!

 

Tried the 4th gear thing, didn't really see anything going on. I do have the B&M shifter I put on a year ago so could be a false negative. Noise doesn't really come from the trans but if I have the vehicle jacked up and spin a wheel (by hand with hands at 9pm and 3pm) back and forth there is a metallic noise when it shifts direction (not a continuous clicking like that of a FWD car with bad CV joints). Front and rear wheels both make this noise. It is not up and down movement of the wheel, just changing direction of spinning. You can see how accelerating or decelerating exerts more force on whatever is making that noise. I am assuming it is not normal?

 

Rear could be pinion bearings, wheel bearings or spider gears going. Wheel bearing is the easiest and least expensive fix.

 

Bearing noise is usually a continuous hum and I have had and replaced bad wheel bearings before and it's not that. Just watched someone work on a XJ spider gear on Youtube and that sounds like a good lead. There is some kind of slop noise that is accentuated during acceleration/deceleration. I am going to try and grab a video of the noise.

Are the spider gears on a JKU a thing to have this issue around 118k miles?

 

Me and a few other people on here had a hiccup issue upon acceleration with manual trans jeeps. It was fixed by changing the crank position sensor. Cheap and easy thing to try. Though I don't recall any clunking noise when mine did that.

 

Replaced that 6 months ago. It was an easy swap. Didn't make a diff. I do think I have two issues going on and one making the other worse. I don't have any codes thrown (I do have JSCAN); is there anything else I can check values of in JSCAN for something that is off enough for a symptom but not enough to throw a code?

 

I had cleaned my MAF sensor with MAF cleaner and that did NOT really do anything. Disconnected the battery and touched the terminals together for a minute to "reset things" also.

What I did find is that I removed the MAP sensor from the right top side of the engine (Pentastar 3.6L as you are looking at it) and thoroughly cleaned with MAF cleaner spray. Did the battery "reset" process. This made a huge difference. MAP sensor original and could still be bad but things seem 90-95 percent better. I hope this helps someone else out. Didn't cost any $ since I had the MAF cleaner spray on hand.

There aren't any videos out there on this but the sensor is on the front of the engine, right side, near front (as you are facing the motor) and it spins about 180 degrees. You spin it half way around then gently pull up. Shouldn't need to force or pry it up. Plug is easy to disconnect unlike the coolant temp sensor which is confusing to someone who hasn't done it before :-).

 

I just got used to the "jerky" feeling on my manual '13. But I'm gonna give this a try. Thanks for posting!

 

Definitely clean em both and maybe one at a time then test drive to see if either had a more positive effect. Someone may have an electrical test to validate either's accuracy but the MAP sensor is around $20 if you want to go crazy. MAF's are usually pricey. There are some nice videos on Youtube of how to take the MAF out carefully, it's a little more involed.