Rhythmic Thump?

[Poppy360]

I'm not sure when it officially started, but my jeep has developed a rhythmic thump. I feel like it's coming from undernieth and behind me, sometime it feels like it's under my seat. It happens at all speeds and increases in speed with increasing MPH. (I'd say it happens @4x/sec at 25MPH) The thump is most noticable at 25-35MPH. After 42MPH I'm not sure if it disappears or just gets turned into a vibe.

I rotated my tires over the weekend and that didn't do anything. I reset my pinion angle yesterday and that didn't do anything for it, but I did get rid of all my high-speed vibes. smile.gif I also jacked up the rearend, put the tranny in neutral, and spun the DS by hand. I didn't feel any binding. I installed a Tom Woods CV shaft and AA HD SYE in the Spring. I checked the joints on the shaft and they are tight. The only slight play I found was if I pushed up on the output shaft of the TC it moved a bit. There's no leakage from around the shaft. When the jeep was jacked up I spun each tire and didn't feel any binding or hear anything of concern.


Any ideas? I'd kinda like to get this settled before snow flies...again.

Oh, I put in an 8.8 during the summer, but this started recently.

[ItsaCJ6]

Exhaust bouncing around ?

[ElGuapo]

have you greased your universal joints on your drive shafts?

[Poppy360]

Exhaust bouncing around ?

It is, but that wouldn't cause such a perfectly timed thump.

[Poppy360]

have you greased your universal joints on your drive shafts?

I have been, but it has been 3K since the last lube. I'll try give 'em a lube when I get home.

[ItsaCJ6]

It is, but that wouldn't cause such a perfectly timed thump.

Yes it can if its hitting the DL.

[Poppy360]

Yes it can if its hitting the DL.

It's only hitting a shock.

[ItsaCJ6]

It's only hitting a shock.

Copy that... hey could be alot of things even a loose wheel, it's gonna take some time consuming investigation.

[Poppy360]

Lubed the joints...wasn't them.

[rokcrwlrtj]

bent axle shaft maybe?

[Poppy360]

Wouldn't that create a significant vibe at higher speeds? Or at any speed for that matter?

[Geesh]

I'm used to this happening on a few of the vehicles which I've driven over the years. More often than not, it turned out to be a split/broken belt on a tire. You may feel it if you slide your palm over the tire (some wine and foreplay helps); there will be a rise, maybe an egg or a long raised edge on the tire's surface.

Other things have been bearings or out of balance tires . . .

Good luck

[Chato]

Do have radial or bias tires? Bias belt tires flat spot when parked and then thump for a while until they warm up, especially in cold weather.

[Mike CZJ]

quit listening to techo music....