Strange noise coming from drivetrain?

[Colo.TJ]

After doing Wheeler lake on saturday I starting getting a strange noise from my drivetrain somewhere. At first it made a faint thumping sound only at higher speeds over 30mph. I got it off the dirt road and on a paved road and the rythmic thumping was still there only at higher speeds. The thumping did "thump" faster the faster I was driving. I pulled over and looked underneat and found nothing. I had my wife drive forwards and backwards in 4lo and 4hi and two wheel drive and could hear nothing. I continued down to Breckenridge and the thumping did go away but was replaced by a kind of clicking noise that was more apparent under decelleration than under load. I drove it back to Denver w/ no adverse effects and the noise seemed to lessen. I drove it again on sunday to the cleanup in Carnage and the noise was still there though not as apperant.
Any Ideas? Where should I start looking?

[satan]

While it's always difficult to assess 'noises' on a discussion forum - I would strongly advise pulling your tire/wheel assemblies off and opening each of your differentials for inspection.

Removing the tire/wheels will allow you to look for odd things lodged in/near brakes and the wheel plates...

Changing your diff fluid (covers off) will allow you to rotate your ring gears to assess any damage to them or their pinions (wipe each tooth dry and feel the surfaces and pay close attention to what drains out and what chunks remain on the bottom of the diff) - remember, "Gear lube is not metallic"

That should cover most everything aside from a u-joint inspection and a functional check of your lockers (to assess them and your axleshafts).



From your narrative, I'd suspect that there's a mark on the "coast" side of a tooth in one of your diffs (most likely the rear) if the clicking is at tire speed then really look/work over the ring gear... if the noise is more frequent, then suspect pinion damage.

(My reasoning: is that a forign body wedging between the loaded gear surfaces causes extreme pressures to be developed forcing things apart each time that tooth is loaded; Later on, once the tooth is damaged and the foreign body is expelled or destroyed, the High pressure "thump" is replaced by an open tollerance "click" since the surface of the tooth (or part of the tooth) has been removed. The reason that it is not so noticeable the second day is probably due mostly to lubricant temperature and the related viscosity change (thicker fluid is quieter)

[Colo.TJ]

Satan, Thanks for the quick reply. I will do that. One thing is that the noise seems to be coming from the front passenger seat area. Could a noise from the front or rear diff. seem to come from that area?

[Colo.TJ]

Anybody else?

[upnover_yj]

Well is that the side you rolled onto(?). If so you should check every bolt on that side "twice". Something could be loose and vibrating. Just a guess. Good luck.

[satan]

Originally posted by Colo.TJ
... the noise seems to be coming from the front passenger seat area. ...

Well - look to possible other solutions relating to the motor mounts and exhaust -- you do have a belly-up, which alters some of the mounting for those things...

Have you fully eliminated your driveshafts (upper joints?) as the source for your noise?

Also your long arm bushings could be a part of the puzzle (like a bad u-joint out on the front wheel thumping up through the long-arm to it's upper mount... or something)

[jolleyman]

Check the tranny mount (if its stock) as well.

[Colo.TJ]

Well the problem has been found. As Satan suspected I chipped a tooth off on the pinion gear. I found it wedged between the ring gear and the detroit locker. It was about 1/2 to3/4 of an inch long. The ring gear is in pretty decent shape considering. I removed the peice and made an appointment for a new ring a pinion for next week. Unless someone knows someone who can do it thurs. or fri. of this week.

[satan]

Damn... it never hurts to check, but the "noise change" was a giveaway...

Sorry to hear of your loss (how come there aren't Jeep Sympathy cards?); I'm all too familiar with that sound!

About the only place that I'd even think about trying to gear in the timeframe you mention would be at Marlen's Tire in Ft.Collins (on 287) - the tech to talk with is "Jon"; great work and quick turnaround.

Good luck - and keep all the metal that comes outso you can 'prove' that you got it all out and that nothing "extra" came with it..! (like a jigsaw puzzle - try to account for every piece by 'rebuilding' the missing pinion tooth - extra pieces may be detroit parts and too few pieces means "keep looking"...)