Adventure

Last night the Jeep started up with a new noise. I heard a pop and then a steady knocking or banging. The knocking was not aggressively loud and its frequency was directly related to the speed I was driving. It also sounded like it was coming from behind me. I am suspicious it is the axle, I also have never worked on any axle projects.

The Jeep has a 3.5 RE lift with the full spring packs. I have not modified the axle or installed the t-case drop to help with the axle angles.

Currently my only idea to isolate the noise is to pull the rear shaft and drive in in FWD (4wd) to see if the noise disappears. Anyone have any other ideas of what the noise could be and any easier solutions to figure it out.

I need to solve this quick as I was planning to drive the Jeep to see family for Thanksgiving. Thanks for any help.

SeriousOffroad

Pull the rear diff cover and take a look at the spider and side gears.

Ianf406

You can also Jack up the rear and spin the tires- see how it feels/pinpoint where the noise comes from (assuming it also happens at really low speeds)

OxfordCherokee2

Sounds to me like it could be u joints in the drive shaft. You should be able to tell if that is the problem pretty easily. Just grab ahold of the driveshaft and see if there is any play in it. If there is you have found the problem and its a pretty quick fix with a hammer and pair of pliers. Once the driveshaft is out of course. If you didnt put an SYE on or a t case drop this could have cuased more wear on the u joints.

kgm

First thing I would check is the u joints. I just went up 4.5 in the rear and am getting a new driveshaft. It's currently pretty noisy at certain speeds. I've been staying at home or riding my bicycle when I can!

Adventure

Checked rear driveshaft.. Rock solid all looks good. Did not pull rear axle cover.

Some research led me to check front driveshaft as well (my ears may have misled me to the rear). Found some play and may have discovered the culprit. Here's some pictures:





I'm not an axle guru but the way it moved when I grabbed the axle didn't seem right. I also suspect this piece should not be separated.

Now begins the research. Please share any insight, encouragement, or just poke a little fun at some misfortune.

driveshaftron

hey you got to put the jeep in neutral to ckeck the driveline chock the jeep put in neutral and then check that way thers no weight on the shaft grab the h yolk and see if slop check the stub if slop push yolk up and down side to side if trunion moves ujoints bad most of the time the ball stud and centering yolk go bad because of lack of grease especaly if it has that rubber boot thers no grease fitting

OxfordCherokee2

That should be separated like that, it allows the axle to droop. However there should not be any play in it. To check that's the noise take out the drive shaft and drive it.

Adventure

Thanks for responses and pm's.

Both shafts seem the same after putting transfer case and transmission in neutral. Very small play in rear which seems to just come from being in neutral.

Saw some fluid on the bottom of the transmission... May have a new suspect.

I recall a brief check engine light two-three weeks ago. Don't like to admit I ignored it after it went away. Time to pick up a code reader and see if we can find any info from the computer.

Adventure

Picked up a code reader... Misfire in Cylinder 6... Do not think this is related to the issue at hand.

Any ideas for debugging the issue at this point?

Only thing on the table is to pull the front drive shaft and drive it around the block to see if that is the problem. If this does not change anything I am still between transmission and rear drive shaft.

Ianf406

Try to replicate the problem in a way that you can have a look at it. I cant even tell you how many times I have found it by jacking it up (securely mind you- good stands) and giving it gas/shaking things.

Adventure

That is actually my next plan of attack.. If I put the rear axle on blocks and give her some gas then I think it should help me narrow down the problem area. This should give me the same affect as taking out the front drive shaft with less work.

driveshaftron

hey any thing i can do to help i run a full service driveline shop so i hope info was good

Adventure

Jacked up the rear axle and set it on blocks so the rear wheels wear off the ground. Gave it some gas and the noise continued just the same as on the road. Put the speedometer up to about 45 mph and the noise only got worse.

Put the transfer case in neutral and repeated. No noise. This tells me that the culprit is the rear drive shaft. Can I get some second opinions on this logic?

I plan to have the GF sit in the seat tomorrow as the brake safety and take a look in the daylight at the rear drive shaft so I can see whats going on.

SeriousOffroad

Again, pull the diff cover and inspect the carrier, side gears and spider gears.