loud pop in reverse

I have a 2000 XJ with a 3" lift. I have already dealt with trac-bar popping issues and resolved them. Currently, when I put the Jeep in reverse and give it gas it makes one loud pop after about 1 foot traveled, then no noise and it reverses fine (just like a trac-bar pop, except not up front). If I just let it idle back instead of giving it gas there is no pop...only when I give it gas. The thing that boggles me is that when I put it in reverse, I have the brake pedal held down and I feel the initial thump of the transmission engaging. After feeling that initial thump you would think that since the only thing holding the vehicle back from moving is the brakes. the drivetrain is under tension and is ready to start backing....so if it was anything between the transmission and the rear brake drums "ie. worn t-case chain" you would think that it would make the noise right when the transmission engages. I am really starting to wonder what it could be and was wondering if anybody else out there has had this experience. your input would be greatly appreciated!! Thanks

Mine does the same thing. Haven't figured it out yet, but I haven't given it much attention due to the million other things I'm working on.

Kevin

When was the last time you looked at your u-joints on the driveshaft? They do need to be greased on a reg. bases. A wore and failing u joint with give that same noise. Grease it up and see what happens. Juice

Do you have the stock driveline? If so, your slip yoke could be binding on the tailshaft, then letting loose when it releases. Have someone view the slip yoke from the side (DON'T have the person lie underneath while you move back). As you put it in reverse and move your rig back, have your spotter check if the slip yoke releases suddenly on the tailshaft.

Typical cure would be to remove the slip yoke and apply some grease on the tailshaft splines / yoke so that it doesn't bind.

Ivan

Ya, know...I am starting to think that it is a u-joint. I have a RE SYE and Driveshaft. After about 2 years, one of the u-joints went bad about 2 months ago and started squeeling like a set of brake pads that are worn down to the metal scrapers. I had all of the ujoints replaced in my rear shaft (3 joints total) since then I have had a mild vibration at around 70 mph...and come to think of it....that's approx. when I started hearing this pop in reverse. I figured out a way to replicate it. If I hold in the brake pedal, put it in reverse and hit the gas with the brake held it will pop. If i put it in park then back to reverse it doesn't pop again, but if I put it into drive then back to reverse it will make the noise every time. i wonder if the backwoods shop that i had replace my u-joints messed up somewhere along the line and maybe one of them needs to be reinstalled? hhhhmmmmm....It almost sounds like it could be coming from the double-cardon section at the front of the rear driveshaft. any additional comments? Does that sound about right? would a worn t-case chain produse the same symptoms? help!

XJ/XRMike said:

I figured out a way to replicate it. If I hold in the brake pedal, put it in reverse and hit the gas with the brake held it will pop.

Click to expand...

Have you looked at what do your springs do when you do that? You might have some axle wrap going which will not help things.

I have brand new springs and it has been doing that before I installed the springs. It does it when only a minimal amount of gas is applied... not enough to get into axlewrap situation.

Mine did that. Took me a while to figure out what it was. Turned out to be the rear axle bearing. At first it was only in reverse when you were aplying gas. Then it started to do it around corners. Try lifting the rear axle. When the tires are off the ground, pull the tire out. The axle should more a little bit. Mine moved almost 2 inches. :shocked: But with how new your Jeep is, that might not be it.