Rear end noise diagnosis... need help!

[wayofjon]

Hello NICO friends,
I had an occasional bumping noise coming from the rear end in my 89 s13 maybe a year ago. It became constant a couple months ago, but I would only hear it when accelerating after a right hand turn. I thought it was the driver side wheel bearing and replaced it, but the sound continued. I replaced both axles and the sound went away, as far as I could tell, for around 6 weeks and then came back. Now it happens whenever accelerating, whether turning first or not. If I put in the clutch it goes quiet. From underneath it sounds more like a clanking, but hear it for yourself on youtube. I think maybe it's the differential but not sure. Why would the sound go away after putting in new axles and then come back? As far as I know, it's the original diff. I appreciate any help or suggestions. Hear it here
[youtube]http://www.youtube.com/watch?v=PEUveTdScv8[/youtube]

http://www.youtube.com/watch?v=PEUveTdScv8

[2_Liter_Turbo]

Pretty cool how you did the video! Lol

Did you check to see if you exhaust is hitting the subframe? I'd double check that first. Make sure all bolts are nice and snug (TQ'd to factory specs) and if all that is good and you know the axles are still good, then I'd say the diff "may" be the issue. What brand axles did you replace the old ones with? Some of the cheaper aftermarket ones have been known to crap out pretty fast which could explain a 6 month timeslot of no noise.

[wayofjon]

Thanks for the response.
I hadn't considered the exhaust. I'll take a look at the position, and maybe I'll put the web cam back under there to see if it's banging on something. I checked the bolts connecting the new axles (which are Duralast) and they're still tight, but I'll have to check the torque on them, and on all the ones relating to the diff in any way. Actually the Duralasts had only been in there for about 6 weeks (maybe 300 miles)... but still that was my first thought. But everything looks lined up correctly and it just doesn't seem possible that one or both of the new ones could already sound like the old ones after they had 180K on them. I'll get back under there tomorrow... thanks for the input.

[waxdnuggz]

Sounds like subframe bushings or carrier bushing. If you push the clutch in and it goes away could be from you releasing torsional torque on the drive line. Lift your car and shake the hell out of the carrier. If you hear a clunk or it moves more then say a half at most then thats a problem may not be the only problem but its one. If you turn and it clunks then I say subframe. If you down shift hard and it clunks then I say carrier but could be a mix of both. Its an 89 and those parts tend to wear out.

[wayofjon]

Thanks for the suggestion waxdnuggz. When you say carrier bushing, do you mean 'bearing' - the diff carrier bearing? If you did mean a bushing, where is that? I wanted to get into it today but a seal went in my jack, so need to go out and find another. Although I was able to reach in there and shove the axles back and forth about 1/4 or 1/2 inch towards and back from the diff and it made a metal on metal bang, but I think that's normal (being that they have springs in them) isn't it? It did sound similar to the clanking when driving... but the diff was also sort-of clanking or making some noise when I was twisting the drive shaft back and forth hard and fast. I would expect that might make a noise when shifting gears, but what about under constant torque?

[waxdnuggz]

Carrier bearing. Sorry man. It was late last night when I posed that. But yes your axels should have a little give in them for suspension travel when you compress the suspension they shrink when you unload the suspension they expand.

Did you have the back wheels off the ground when you were trying to twist the drive shaft. There will be a slight thud when theres no load for the very small gaps between the pieces in the diff but not a bang. Lift the back wheels off the ground and start spining your wheels as fast as you can by hand and then grab them hard to stop them. (Be very careful doing this watch your fingers grab around the tire not in the spokes youll lose a finger or at least break one) wear mechanics gloves. If you hear a loud bang then its driveline if not its subframe

Like i said in my earlier post it might be a mixture of both. Now seems like a good time to upgrade. Vlsd diff, new es subframe bushings, solid 1 pc drive shaft should cost you about 600$ for everything. I know that sounds like alot to just drop but it doesnt have to be all at once. Im currently working on a 1pc driveshaft for cheap and I will be sharing it once I have the few extra bucks and time to finish it. Good luck let us know.