Loud "Thump" from the rear

[Disco69]

Alright, I'm stumped on this one. I have a Detroit in my D44 and have been running it for about 850 miles or so since my regear and locker installed. The last day or so, I installed some lower control arms, a front adjustable track bar and in the rear I changed out my gear oil since break in was complete to Royal Purple 75w-90. After I got all of the arms and trackbar torqued down so I had to go take it out for a test drive. During the test drive I noticed a loud thump when I accelerated after changing gears. Here a couple of my observations:

1. When I coast and then push on the gas it thumps
2. When I initially push on the gas after a gear change it thumps
3. It does not do it when I am in 4wd Hi
4. It does not do it when I am in 4wd Lo

What boggles my mind is that it was not doing this before. Is this just the Detroit loading and unloading? Why wasn't it here before?

[jeeptj333]

http://www.jeepforum.com/forum/f13/03wj-rear-end-clunk-wtf-help-968505/

[Disco69]

Eh?

Should I even drive this thing with it doing that?

[jeeptj333]

didnt have a answer so i was trying to help find one

[akhillbille]

The noise is definately coming from the rear? I've never heard a detroit make a sound like that unloading. I would start by going over all the control arms, tracbar front and rear, shocks front and rear and see where that leads you. make sure everything is tight. Also do you have any torque steer along with it?

[DNA]

I think you hit a cat or something.

[akcowboy76]

The noise is definately coming from the rear? I've never heard a detroit make a sound like that unloading. I would start by going over all the control arms, tracbar front and rear, shocks front and rear and see where that leads you. make sure everything is tight. Also do you have any torque steer along with it?

I would check the Motor Mounts and trans mounts also, maybe the wheel studs to. Just a shot in the dark

[Disco69]

There is definately torque steer, that is how I know it is working. The sound is coming from the rear. I put synthetic in the rear, apparently Eaton doesn't recommned synthetic with the Detroit according to their website.

[naturalbornmudder]

I havent driven the Jeep so I cannot judge, but as a general troubleshooting technique, I would grab a socket set and lug wrench, and thoroughly check the lug nuts first as having them loosen up is something that has happened to me a few times especially with aluminum rims. Next I would check the rear track bar, shock and control arm bolts. After that the driveline.
If you don't find anything there, you can start considering the locker. Typically from what I read the Detroit does unload with a clunk, and the timeline matches pretty well as far as having good break-in on the locker spring. When you first instal a locker everythign is tight and the spring is tight as well. Once it breaks in under normal useage, then that is typically the ride quality and noise that will remain for the remainder of the life of the locker, which in the case of a Detriot probably equals the lifecycle of the Jeep.

[99TJ]

I would start with the U-joints. And from what I've read about the newer Detroit lockers they don't unload the same as the older ones did. Supposedly they are considerably quieter than old ones.

[The Bronze]

I took it for a ride, I don't think it's anything but the locker induced play in the rear axle. We are going to check it out this week.