First off a little background. I have a 2012 JKU 6-speed with 4:10's. I installed JE Reel 1310 front a rear drive shafts. I did not have the inch lb. wrench to check my pre-load therefore I Red loctited the pinion nuts and torqued them to 160lbs. OK I just can't think of a better word to describe the sound and feeling I'm experiencing other than "slack". The sound occurs while in 4LO and idling through rocks/obstacles over relatively flat ground (going up and over them). This sound seems to be coming from the front diff but may also be coming from the rear too, its hard to tell. While there is power being supplied there is no noise but when dropping off of an obstacle and the Jeep accelerates faster than the drive train is propelling it forward there is a distinct clicking (slack) noise when the gears catch. Then once climbing another obstacle it makes the same sound once the vehicle needs to be propelled forward by the drive train again. I'm assuming this is due to the slight void between the ring and pinion gear teeth and what I'm hearing are the teeth catching the front then the back of each tooth with the variances in acceleration and deceleration. Is this normal? Most of my use of low range has been while climbing or descending a technical hill where the pressure on teh ring and pinion teeth is constant, not over flat ground with large rocks to crawl over where the vehicle is constantly accelerating and decelerating. Another thing I'm experiencing occurs during ascents in low range. When there is the need to either stop or shift and I push the clutch in the drive shaft seems to slap back and forth 2-4 times until everything comes to a stop. I seem to remember this happening even while stock but again I was just curious as to if this was normal behavior. Both of these cases seem to only occur during the use of low range. I'm not experiencing any abnormalities during daily or freeway driving. Now that everyone reading this is thoroughly confused any insight into this is much appreciated...haha. Thanks in advance (considering you were actually able to read through my entire post...haha)

 

From what you have described seems to me it must be the front. You said it doesn't happen when daily driving....sounds to me like the rear should be good. Does it happen in 4hi? Do you notice 'play' in the u-joints?

 

No there is no play in the U-joints and when you grab the drive shaft and try to twist it back and forth while parked there is very little play. Compared side by side to a stock JK the play seems to identical. I didn't seem to notice it in 4HI but that doesn't mean its not doing it.

 

What you describe is normal, to a certain extent. It's drive train backlash. Backlash from the output on the engine, to the splines on the axles. it all adds up, and seems amplified in 4lo.

Now, the other issue is the torquing of the pinions. That should have been done correctly to ensure the crush sleeve is still functioning as designed. That would have involved taking a torque-to-rotate reading before dis-assembly, and re-torquing a certain amount more on final assembly.

So, it's possible your preload is incorrect.

 

Incorrect preload wouldn't affect the backlash though since he didn't remove the pinion shims. However, if the preload is not right, it could cause the pinion bearings to get reaaaaaally hot...

 

Thought the JK differentials all use preload spacers instead of crush sleeves?

 

My 08 still used the crush sleeve to set the pre load on the pinion bearings.

 

Yeah backlash is the perfect way to describe it. It doesn't seem to be in excess. I think it just sounded different because I was going through a narrow slot canyon with the Windows down so everything sounds amplified.

I was hesitant to do it this way but it seems most people do and, have good luck with it. Also I talked to Jim at JE Reel and he said I should be fine torquing it to 160lbs. And one of my mechanic friends said the same thing he just recomended not to over tighten it. I have 1000+ miles on them now (not nearly that many on the front under power) and haven't noticed anything out of the ordinary. It seems all is good in preload land for now. If problems do develope about how long after the install would/did the signs and symptoms start to show? Just would like to know what to keep my eye out for. If I do overheat the bearings its a good excuse to get a PR44 right?...haha

 

Bump......

 

The noise in 4 low of the drivetrain "slop" is just because of the gear reduction of the low range is "amplified" like that one dude said. And I doubt the pinion nut turned much if any when you torqued it to 160lbs. And I'm curious how you held the flange when you torqued it. When you actually crush a crush sleeve, it takes a lot more than 160 lbs. I use a piece of steel stock with bolt holes drilled in it to bolt it to the flange, and it has a 1/2 drive hole I put a breaker bar into, then rest it on the framerail. Then use a 36" long ratchet to turn the pinion nut and it takes a good bit of force. Also did you " stake" the pinion nut? A beam style inch-lb torque wrench is what you need to check, it and also the carrier/ring gear needs to be out of it. Used bearings should be between 5-10 inch-lbs of rotational torque (the force it takes to keep the pinion moving not breakaway torque which is the term of the amount of force to rotate the pinion from a stationary position to it rotating).