[UnDeR EsTiMaTeD]

Just recently I've noticed a slight knocking noise when letting off the gas pedal. I don't feel the knock, I can just hear it. It seems to be coming from behind me; towards the rear-end. It happens as soon as I take my foot off the gas and it is definitely more prone to happening at speeds of 35MPH or slower. What could be causing this? I just replaced the u-joints about 200 miles ago, but I'm almost positive the noise was there prior to the replacements.

Thanks in advance.

[Varkyl]

how many miles are on the Jeep?
from the sound of it, the cause is the backlash on the ring and pinion. Mine is doing close to the same thing, and is going in for a full rebuild and upgrade on Thursday.

[02Lightning]

Check you u-joints to be sure they are tight and you didn't forget somthing.

[greasefingers]

I agree, check the easier & cheaper stuff first. Start by checking the U-joints.

[UnDeR EsTiMaTeD]

The Jeep has about 200K on it. The u-joints are tight and don't seem to be the problem.

[Varkyl]

while you have your foot on the gas, just driving along do you hear a whine? and when you let off it stops?

[UnDeR EsTiMaTeD]

I don't hear any whine. I will try to listen when I drive home today.

[coolest_Stan]

i ahve the same problem, and I hear a whine kind of. I probaly have the same problem as under-estimated

[Varkyl]

the whine when on the gas and a "knock" when off is going to mean a rear end rebuild. I know this because as I am in the same boat. But mine was a little worse as it was starting to vibrate at times. And it was definately coming from the differential. It's all ok though its getting a bunch of fun parts while it's being done.

[sgtcherokee]

check your pinion in the rear ! if the bearing is going bad you will get slop when there is no torque on the unit .

[UnDeR EsTiMaTeD]

Well, not the best news, but how much am I looking at for repair? I might not be able to afford it for a few months...

[Varkyl]

well in my case with a complete rebuild including all new bearings, seals, ring and pinion, limited slip and labor; about 1100 to 1200 (est) and if I choose about another 300 for upgraded axles.

[UnDeR EsTiMaTeD]

Is this a repair I can put off for maybe 3 months? I just spent about $3000 on a brand new transmission. I don't exactly have cash to spare.

[Varkyl]

mine was doing it when I bought it at about 167k now at 179k and over a year later I am getting it done because I am tired of it doing it. (And besides bigger tires need lower gears).
So putting it off for a while shouldn't hurt anything.

[zjhitman]

Nobody has mentioned checking the lower control arm bushings yet. Especially the ones closest to the axle. My 97 eats lca bushings. Getting ready to put in the third set at approx 228,000 miles. The front ones are the absolute worst. Think I will go with poly next time.