Hey, I have a 95 2.5l YJ, auto tranny, np231, offset dana 44 in the rear and the d30 up front. I regeared the back to 4.88's but i havent gotten a chance to install the front gears. I have not put it in 4wd, but I have kept the front driveshaft connected.
I am getting a slight noise around 30 mph, then around 50 its gets very bad. But once i let off the gas the sound will stop. The noise doesnt sound like a grinding, but it does sound like some type of metal noise.
I checked the axle, the axle seems to be fine and I checked all of my fluids just in case. The tranny seems to be running fine so i dont believe it is that, but what do i know... :confused:
Sorry for being so vauge, but I have no ideas where this could be coming from. What causes a noise that will go when i am accelerating, but once i let off the gas the noise goes away???????????

any help would be appreciated,
thanks :beer:
nick

Who did the gear install? If a shop, did you just drop it off, or did you pull the axle yourself and bring it in?

Bad gear install, rear driveshaft out of phase, bad u-joints in rear driveshaft, bad pinion connection (I'm rusty with Jeeps, is that a slip yoke or a flange?). If a flange, loose flange bolt.

Can you tell if it's located near the tranny, or behind it?

Basically, anything back there that spins can cause noise during either accelerating, decelerating, or always.

My friend and I did the install, and he has done many so i think thats not the problem. The new axle only has about 3000 miles on it with new everything. I drained the gear oil and there wasnt any big chunks or anything wierd in there, so i am hoping the axle is fine. I checked the ujoints and they are fine. Is there any way to check to see if a driveshaft is out of phase? I still have the slip yoke :barf: so i cant pull the driveshaft and drive it in front wheel drive to try to pinpoint the noise a little better. Unless I can clog it or something for a short test drive..i will have to look at that a little more.
The noise sounds like it is coming from directly under me, but then again it is a jeep so pretty much the whole rearend is under me.....
Thanks for the help, I am gonna go out and try to see if i can check for other things that it might be. Its hard to work on it since i have to do it in our campus parking lot and they dont allow you to work on vehicles.

thanks for the reply :beer:
nick

why not pull the driveshaft and see if the ujoints are bad?

I did, and they seem fine. The reason I was going to do that was to see if it is something in the rear axle/driveshaft or if it is a problem in the transfercase. Is there an easier way to check the xfercase without dropping it and seeing if there is any problems with it?
thanks
nick

Pull the rear driveline and run it on the front only.
This would eliminate the rear d-line and gear setup

nick.. pull the rear driveline.. it will leak a little fludi.. dont worry..
just refill it when you are done..
use atf for it tho..
if the noise is still there.. remove the front shaft.. try it again..
if the noise is still there.. then look into the transfercase..
how hi is the lift on the rig?
if over 4" did you drop the transfercase?
to keep the driveline close to normal?
check the transmission also.. it might be a bad syncro or bearing.. ..
how many miles on the clutch??

there are so many difernt things to check ..
it might be the whine from the gears also.. but the difernt gear ratios are a good factor.. remove the front driveline and see if that stops first..lol

well....if the noise was not there before the gear install....and after the gear install the noise is there....well, I put my money on the poor install. How did the painted pattern look?

That's where my money is too. Even if the install seemed good when you did it, things can go wrong. Maybe you had a piece of grit between two shims, and so the specs were good upon install, but now the shims are loose. Maybe someone banged something with a wrench at the end, and didn't tell you. Maybe it was bad gears. Just because the guy has done a few installs doesn't mean this one was done right. I suggest pulling the cover and crawling around in there a bit.

How about the trany mount?

I had a good install in my rear for a while, but then the pinion bearing took a crap and killed everything... I didn't know this for a long time and thought that my transmisison was taking a dump due to the whining... I finally broke the pinion while driving one day, replaced the axle and it drives as quiet as a cadillac now... ok maybe not that quiet but I can at least hold a conversation while driving now.

lol.. I installed the gears in my jeep and after the accident they whined so loud i couldent hear the radio.. so I checked the axel and it was slightly bent..
it was the tires making the whine..
the drivers side was good.. but the passenger side had a 10 deg tilt on it.. it was closer at the top than the bottom..
which gave alot of noise..


what tires are you running.. are they the same as what was there before the regear?

thanks for all the replies.
mikeswrangler - I swapped axles and new gears at the same time, but everything else was the same.

i looked in the diff and everything seemed to be fine. There wasnt anything that was loose and the teeth looked fine. I havent had much time to crawl around under it cause i have been busy with school, but now it is the weekend. Would it be wise to just pull everything out of the axle, shafts and all and just see how everything looks? It cant hurt unless i am a moron and cant figure out how to get it back in....hehe
if i undo the driveshaft, jack up the axle and spin the tires, if a bearing or whatever is bad would it make a noise by just a little spin?
i checked the tranny mount and it seemed fine...it didnt wiggle and doesnt that mean that it is ok??

ahh, this is pissin me off...hope its nothing to bad. guess i will have to just wait and see.
anyone else?? thanks again :beer:
nick

Put the rear end up on stands and start the engine. Get those wheels moving, then CAREFULLY crawl around and find the noise.

If it's a bad install, you won't *see* anything out of spec, you'll have to make backlash and preload measurements.

I pretty much guarantee the noise is the install, either gear whine, bearing whine, or some combination.

i was thinking, if it was the gears, why wouldnt it make the noise all the time????
i went out and took out the front shaft just to see what would happen, and it didnt make the noise as bad. For about 10 min of driving it didnt make a noise but then it started again on my drive back...todays drive almost made it seem that the noise gets worse when everything heats up...i dunno. the only jack that i have here is a little bottle jack so i am gonna have to wait until i can get a floor jack or something.

thanks again, i am gonna try to try some more suggestions before class and hopefully i can figure something out. thanks again :beer:
nick

Originally posted by njc
i was thinking, if it was the gears, why wouldnt it make the noise all the time????
nick

Because that's what gears do. If it's a bearing issue, then under load in one direction, you are loading the bearing to specs, but when you take off the throttle, the bearing gets unloaded. Same with the gear mesh. The whole damn thing flexes some in there, the backlash/preload specs are designed to allow so flexing without getting everything out of alignment. If the backlash is too tight, then the gears will work fine until they heat up and expand, then the clearance is too tight and they'll bind.

There are a dozen things in there that can make whines if not setup correctly. If you keep driving on it, you can and will blow the gears catestrophically.

well with that said, when we did the gears he said that the space between the pinion and ring gear was a tad bit bigger, but he said that it wasnt too big it would hurt anything. Could it being to big cause the same effects as it being to close?

ahhhh!!!!!!!!!!! i just pulled the rear shaft and drove it in front wheel drive and it didnt make the noise :( so it is comin from the rear axle, but where? i know the basics on axles, if i tried to pull the shafts and all that would i be able to tell what is messed up inside by examining everything???
thanks
nick

It seems to me that is almost certainly the diff. Did you watch your freind install the gears? If so did he make any measurments, or check the mesh pattern with marker grease? I've had a lot of non wheelin friends tell me that they can setup gears. When they do, the axle will last for a while, and then when it blows, they think it is because they were hard on it, or because their engine is so powerfull and they do a lot of burnouts, etc. Upon questioning them, they thought you could just bolt in the new gears, torque the bolts and you were done. In reality it is an art and it takes several hours to get everyhting shimmed correctly. You usually have to test and then retest the mesh pattern before you will get it right. It will usually take a very experienced person several attempts before they get it shimmed correctly.

yea.. several attempts :flipoff2:
it too me the frist time I did it about 4 days to set it up.. it would look good and after I ran it it started to wine and growl.. first on the power side.. then the coast side..
one shim makes a big differance

also you need a impact that will go to 450 ft lbs for the pinion nut..

for the crush sleave

if that is not crushed right it will slowly crush on its own and mess the settings up..

i watched him do it and he measured everything. i will put some more paint on and try to post a pattern of how it looks. tomorrow (or today i guess) is going to be the day that i check on it. just gonna pull everything apart till i find something wrong with it. hopefully i can notice it....
thanks for all the replies, will let you know what happens tomorrow :beer:
nick