Thump thump thump

I feel stupid asking this question, but here goes.

About two months ago a thumping sound started in the rear of XJ during rainy/wet/snowy weather (sometimes the day after a storm).

The sound seems to emulate from my rear drive shaft when I'm traveling between a crawl up to 15mph. A distinctive thump is heard, then another and then another increasing in periodicity as I speed up. If I maintain the same speed, the thump sounds at the same periodicity. The strange thing is that sometimes it sounds like it coming from left or the right rear wheel and then other times it just seems to come from the center of the XJ's rear end. Usually after I drive at high speeds the thump will go away at subsequent low speeds (until I park it or drive through a puddle deeper than a half of an inch). Sometimes along with the thump I feel a pulling feeling like something is sticking, trying to stop my forward motion.

Due to the symptoms it seemed to me to be some type of corrosion problem between my transmission the rear wheels. I lubed up all the pivot type joints on the axel. The Jeep seemed to drive smoother, but the thump came back the next rainy day.

I did change my drums, their pads and all springs (etc) about a month before this problem started. I think it might be the Universal joint but I'm not sure. Any suggestions?

Tires balanced lately?

Put new BFGoodwrench All-terrain T/A KO LT 15'' 245s on in December. They're balanced and I keep the air pressure between 40 to 42 PSI.

The problem started about a month and a half after I replaced the tires, a month after the rear brakes.

Lubing an already gone u-joint will only hide the problem for a while. Pull the rear shaft and inspect the u-joints. Rotate them and listen for a grinding noise. Pull a bearing cap and look at the needles, just be careful not to let them fall out.

Dirk Pitt said:

Pull a bearing cap and look at the needles, just be careful not to let them fall out.

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Especially if you are working near a haystack. Then it'll be like... hmmm, I dunno.

The kidneys are good, but you right it allows you to feel the road.
I keep it between 40 to 42PSI on the pavement for gpm.
I lower it to 30-32 in the dirt.

This only happens on a wet road or is it that the roads have just been wet since it started.

It only seems to happen if it is raining, snowing/sleeting (just about the same thing in Virginia) or I happen to drive through some decent size puddles. Sometimes the thumping will re-commence the day after the precipitation.

i would take another look at the rear brakes. moisture in drum brakes will cause them to grab. in your first post you said it pulls or drags, i would think brakes. they also need to be adjusted periodically.