I'm running a Currie HP 9" rearend, with a Detroit locker.
It's got about 40k+ trouble-free miles on it.

Last week it started making this 'pop' sound. Let's out one 'pop', when I go from Park to Drive and give a little gas (more than idle, but don't have to punch it to reproduce). Happens sitting still too, if I ride the brakes, and load up the drivetrain in reverse, then go to drive and give it some gas; one 'pop' then everything is fine.
I can feel input in the gas pedal when the 'pop' happens. I haven't wheeled it since this 'popping' started, at least I haven't noticed it until now. Nothing has changed. I did find my retaining nuts on one rear axle flange were loose. The seal got toasted, so I replaced the seal. Could damage have occured to the side gears on the side with the loose axle flange nuts? Is the 'pop' something to worry about? I know, "it shouldn't pop", but is this an acceptable sound from a detroit? The Detroit has been a painfree champ until now. Any suggestions on what this could be?

Thanks,

easy solution would be u-joints, get under there and try to move the driveshaft while in park, if it moves excessively they're probably shot...if thats not it you've got bigger probs

Be sure you check the rear control arm bushings and the control arm mounting bolts. Might sound too obvious but just a slight bit of wear or loosening of the bolts can cause similar noises.

I was planning on dropping the rear driveshaft and making sure it's coming from the rear and not the tcase.
I did checkout the joints while having someone else do the reverse / drive think to reproduce the sound; sounds like it's coming from the housing.

I'll checkout the u-joints too, thanks.

I've had the same problem twice and both times it was the driveshaft u-joints. I even pulled the d-shaft before replacing the U's to inspect it but you couldn't tell because there were no real signs of wear when assembled.

driveshaft u joints:flipoff2:

i drove around for a month trying to figure it out!:rasta: i have a two piece rear toyota shaft. i thought it was the center driveshaft support. it was and the u joints!:rasta:

Well this is weird...the sound is gone.

Last night when I got home, I put the Jeep in 2wd lo, and did the drive / reverse thing to replicate the popping. I had it so the rig was basically doing a power braker (if somethings wrong with the rearend, I'd rather find out in my driveway then on the Old Sluice this weekend! :rasta: ).
This morning, I crawl under the rig and check out the control arm joints and u-joints. They all look and 'feel' good. I couldn't get any play twisting the arms or shafts, and couldn't get any slop with a pry bar.
So I put the rearend up on jackstands and try to induce the 'popping' in the usual manner. It won't happen. Tried in 2wd lo and 2wd high. On top of that, the rear brakes won't keep the tires locked even with light pedal. I know I need to bleed the brakes, but I would've though I'd had more brakes than that.
I'm thinking my pads got fried with gear oil when the flange nuts got loosed (there was gear oil EVERYWHERE, fawk I hate that stuff), and maybe the popping is coming from them. Going to replace them tonight for good measure.
Also have NO ebrake left; had some, weeks prior to the flange nut thing.
Thanks for the tips guys! :beer: