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T case? front diff? tranny?

989 views 6 replies 5 participants last post by  Mattaeus 
#1 ·
Hey guys,
I am having some weird noises coming from somewhere. It started with a high pitch "whine" during cold mornings and would eventually work itself out. You could only hear it when coasting to a stop over 20ish MPH. Recently the sound has gotten louder and is present at all times. If I am going over 10MPH it is very noticeable and over 50MPH the sound is masked by the engine so its not super loud. Pushing in the clutch or putting in neutral does not make the sound go away. If I am in 4wd it is still there... I want to say the noise up at the front diff but its so hard to tell so I am not convinced its not the t case or tranny. I have not tried any fixes at this point as I am not sure if this is a real problem, any advice appreciated. My thoughts are a wheel bearing or other bearing on its way out..

Probably unrelated,
When driving in low gears (1st,2nd) and I am on the gas in a high RPM, if I let off of the gas it will make a loud clunk noise. This is likely due to slop in the drive train but figured it was normal, anyone else have this? When in neutral both of my driveshafts have enough play in them to be jiggled by hand about an 1/8th of a turn, normal?
 
#2 ·
Do you hear it when you are idling at a stop light or in a parking space? If so, it could be the serpentine belt, the idler pulley, or the belt tensioner. A trick i was told is to let the jeep get completely cold, preferably do this in the morning after it's been sitting over night, and take off the serpentine belt. Then crank the jeep and listen for the squeal while parked. If the squeal goes away it is something belt related. If it is still there you can at least dismiss the belt and pulleys. You only want to keep the jeep on for a very short time. I only needed about maybe 10 seconds before i figured it out and then quickly turned it off and put the belt back on. Hope this helps.
 
#3 ·
I don't hear it idling or when I rev the engine at a stop. I am convinced this problem is getting worse but am reluctant to take it to a mechanic after getting hosed last time. I will likely wait until failure which sucks but I also think this might be the cold weather...
 
#4 ·
The first thing I would do is check the fluid level/condition in both axles, trans, and tcase.

Regardng the axle shafts, in 2Hi you should be able twist the front shaft like you described (~1/8 turn), but the rear you shouldn't be a able to twist. In 4Hi/4Lo you should not be able to twist either.

The whine I had ended up being a bad rear-pinion bearing on the rear axle.
 
#5 ·
The first thing I would do is check the fluid level/condition in both axles, trans, and tcase.

Regarding the axle shafts, in 2Hi you should be able twist the front shaft like you described (~1/8 turn), but the rear you shouldn't be a able to twist. In 4Hi/4Lo you should not be able to twist either.

The whine I had ended up being a bad rear-pinion bearing on the rear axle.
So if I can twist my rear axle, what does that tell you? and to clarify are you talking in neutral or in gear? Pinion bearing would make allot of sense and id imagine it would squeal in the front regardless of being in 4wd or not...
I changed all my fluids about 2k miles ago and the noise was present before I did that so safe to rule that out, I did notice quite a bit of sludge in the axles, specifically on the drain plugs but it seemed normal(ish). I also had a small amount of metal on the tranny plug but heard that is normal? I do have hard shifts between 1st and 2nd when cold but again I heard this was normal, just want to put up everything I noticed in case they are related. Thanks for the help!
 
#6 ·
If you put it in 4H and park on a slight incline so there's a little bit of rotational pressure, you should not be able to rotate either driveshaft. If you can still wiggle it left/right, it likely means you need new U-joints. Bad U-joints will likely cause excessive vibration under acceleration or deceleration. Deceleration is the most common in my experiences and observations.
 
#7 ·
I'm dealing with a similar whine (because I think the shop just improperly installed new 4.88's) . I've had driveshaft u joint failure before and they didn't whine, they clunk, and they're easy to diagnose. Just grab the driveshaft and give it a good rip, or if any of the little plastic cap boots are damaged, the joint is most definitely fudged.

We're talking about driveshafts here, not axle shafts.

So last night while it was whining away at 40mph, I popped it into neutral, whine went away. But I've noticed it only whines when accelerating, and a little decelerating.

I then popped the rear diff cover and changed out the shiny metal filled oil. Removed both driveshafts.
Put it on jack stands.
Fired it up, and hit the gas pedal. NO WHINE.

I believe I can rule out transmission and transfer case. That would leave me with improper ring & pinion setup or just plain bad gears, improper pinion depth/torque, or bad pinion bearing.

Just wanted to show you what I've done to diagnose the whining/whirring. Our cases sound similar so I'd take a hard look at the rear differential, especially the rear pinion.
 
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