Biotex Posted July 16, 2013 Share Posted July 16, 2013 Scenario: Stock NP231 in 2wd Open Dana 30 with axle disconnect collar locked in the open (disconnected position). all 4 wheels on the ground. The front shaft should spin freely correct? If I slide the collar over to connect the passenger side axle, it should not spin freely correct? What does the two piece passenger side axles ride on at the disconnect? bearings or bushings? Please read the following carefully, as I have included a lot of facts related to the noise, and might save you from asking a question already answered. I could really use some help on this one, so please offer your suggestions. I'm trying to diagnose a low pitch whine that is cyclical with wheel rpms, and am trying to eliminate components. So far it is definately not the rear drive shaft or rear axle. It is not tires. I don't think it is front drive shaft either, because I believe I have it not spinning due to the above scenario. It spins freely when I crawl under the truck and spin it by hand. I feel absolutely no slop in the output bearings from the transfer case when I grab the shafts and violently shake them. After driving the truck at highway speeds, I feel no abnormal heat coming from the front joints in the knuckles. Brake rotors appear in good shape, but will point out the noise sounds like gears or bearings, not warped rotor noise. All fluids are new and within specs. Noise is the same no matter what gear I'm in, whether clutch is in or out, power on or coasting. By the way, I have put the truck up on four stands in 4wd and 2wd, and cannot pinpoint any abnormal noises. This fact points me to front wheel bearings, so I'm thinking that is my next step. :wall: Link to comment Share on other sites More sharing options...
Biotex Posted July 16, 2013 Author Share Posted July 16, 2013 Just wanted to mention that I can hear the whine of the gears as normal. It is a seperate noise. The noise I'm hearing is much lower pitched and a cyclical pattern that matches wheel speed. I don't believe it is a rubbing speedo cable or my gauge would jump. It is surprisingly steady. Link to comment Share on other sites More sharing options...
ParadiseMJ Posted July 16, 2013 Share Posted July 16, 2013 The shaft should spin freely in the open position (and not spin at all when moving). I had what I thought was bad axle u-joints, which after much of the same diagnostics, turned out to be a loose wheel...the lugs were only finger tight. Just throwing that out there. I've also had a slightly bent dust shield that was just barely rubbing the rotor, but making a lot of noise. Link to comment Share on other sites More sharing options...
Akula69 Posted July 16, 2013 Share Posted July 16, 2013 You stated the noise is cyclical with wheel speed, but could it be an engine component, such as the fan on the alternator or the engine fan itself? Ah..I'm 'assuming' the noise is there at idle with my question.... :doh: Link to comment Share on other sites More sharing options...
87Warrior Posted July 16, 2013 Share Posted July 16, 2013 The first thing I'd suggest would be to remove front wheels, followed by the brake calipers. Clean the rotors, pads and calipers guide pins. Do not clean with a degreaser as it can wash the lube out of the unit bearing. My Jeeps always seem to get crud lodged in the front brake components and cause weird noises. The whine could also be a stretched/worn chain in the 231. Link to comment Share on other sites More sharing options...
Biotex Posted July 16, 2013 Author Share Posted July 16, 2013 The shaft should spin freely in the open position (and not spin at all when moving). I had what I thought was bad axle u-joints, which after much of the same diagnostics, turned out to be a loose wheel...the lugs were only finger tight. Just throwing that out there. I've also had a slightly bent dust shield that was just barely rubbing the rotor, but making a lot of noise. I had thought about the dust shield, but forgot to check them. I will look and see, but I think the noise is much different that that. Kind of a low growl that goes wha wha wha wha wha with increasing frequence the faster I go. The first thing I'd suggest would be to remove front wheels, followed by the brake calipers. Clean the rotors, pads and calipers guide pins. Do not clean with a degreaser as it can wash the lube out of the unit bearing. My Jeeps always seem to get crud lodged in the front brake components and cause weird noises. The whine could also be a stretched/worn chain in the 231. If it is a stretched chain, wouldn't i be able to hear it with all 4 wheels off the ground and in gear running? i did that, and crawled all around trying to hear the noise, but couldn't. I will jack it up again and re-listen. Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted July 17, 2013 Share Posted July 17, 2013 Link to comment Share on other sites More sharing options...
mvusse Posted July 17, 2013 Share Posted July 17, 2013 To answer the rest of the first post, the passenger side shaft is supported by the carrier inside the diff, and by the unit bearing on the wheel end. The intermediate shaft has a pin on the inside that rides inside the end of the inner shaft. I have seen inner shafts with both needle bearings and with brass bushings inside the outside end. The shift collar riding inside the shift fork on a few nylon tabs also helps supports the inside end if the intermediate shaft and, only when engaged, the outside end of the inner shaft. Link to comment Share on other sites More sharing options...
Biotex Posted July 17, 2013 Author Share Posted July 17, 2013 Thanks for those pics. I forgot those existed. So that confirms it can't be my NP231 chain because it doesn't spin always. To answer the rest of the first post, the passenger side shaft is supported by the carrier inside the diff, and by the unit bearing on the wheel end. The intermediate shaft has a pin on the inside that rides inside the end of the inner shaft. I have seen inner shafts with both needle bearings and with brass bushings inside the outside end. The shift collar riding inside the shift fork on a few nylon tabs also helps supports the inside end if the intermediate shaft and, only when engaged, the outside end of the inner shaft. Looks like a front axle teardown is in order If I can't find the noise. Reading your post made me think of something. My shift collar is locked in the open position at the moment, because I'm about to swap in some taller gears to match the rears from my new 8.8 swap. Wonder if the intermediate shaft is either rubbing on the collar or the shaft spinning backwards is causing it. Probably not the shaft spinning backwards, because the noise is there with the collar locked closed also. Before I did the rear end swap, the noise was there as well. With the collar open or closed. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 18, 2013 Share Posted July 18, 2013 So you can't shift into 4Wd now because of different ratios? I've seen the little bearing between the intermediate shaft and right hand axle shaft go bad. The noise is there in 2wd, but gone in 4wd. Usually due to a bent front axle tube. Link to comment Share on other sites More sharing options...
Biotex Posted July 18, 2013 Author Share Posted July 18, 2013 So you can't shift into 4Wd now because of different ratios? I've seen the little bearing between the intermediate shaft and right hand axle shaft go bad. The noise is there in 2wd, but gone in 4wd. Usually due to a bent front axle tube. Correct! I'm only test driving it to pinpoint the noise, Plan was to swap in the correct ratio gears, but another project got in the way. I sure hope I don't have to replace those intermediate shaft bearings. If I install a one piece shaft can I do away with them? Link to comment Share on other sites More sharing options...
cruiser54 Posted July 18, 2013 Share Posted July 18, 2013 So you can't shift into 4Wd now because of different ratios? I've seen the little bearing between the intermediate shaft and right hand axle shaft go bad. The noise is there in 2wd, but gone in 4wd. Usually due to a bent front axle tube. Correct! I'm only test driving it to pinpoint the noise, Plan was to swap in the correct ratio gears, but another project got in the way. I sure hope I don't have to replace those intermediate shaft bearings. If I install a one piece shaft can I do away with them? The bearing is easy. It's what causes it to go bad that's the problem...bent housing!! Link to comment Share on other sites More sharing options...
Biotex Posted July 18, 2013 Author Share Posted July 18, 2013 So you can't shift into 4Wd now because of different ratios? I've seen the little bearing between the intermediate shaft and right hand axle shaft go bad. The noise is there in 2wd, but gone in 4wd. Usually due to a bent front axle tube. Correct! I'm only test driving it to pinpoint the noise, Plan was to swap in the correct ratio gears, but another project got in the way. I sure hope I don't have to replace those intermediate shaft bearings. If I install a one piece shaft can I do away with them? The bearing is easy. It's what causes it to go bad that's the problem...bent housing!! Ok, thanks. I'll check it out. Nothing noticeable by my eyes. Link to comment Share on other sites More sharing options...
Biotex Posted July 21, 2013 Author Share Posted July 21, 2013 Found a bad passenger side unit bearing. Problem fixed! Link to comment Share on other sites More sharing options...
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