Howling Differential

[Cliff. Elford]

The original Differential in my 71 240 was very loose and noisy so I purchased a different differential from a wrecking yard that is nice and tight. The drive and shifting improved dramatically but the darn thing really has a loud howl as I proceed down the road. Can anyone tell me if there are many things that can cause this howl or one thing that maybe I can correct myself. The noise was bad enough that I changed back to the old diff. I have not yet tried to take it apart . Any ideas? thanks.

[2ManyZs]

There's only a couple things that could cause the howl, bearings or the ring and pinion itself. Best thing to do is to pull the rear cover and see what the ring and pinion look like.

Hopefully it will just be one of the bearings that is going bad, and hasn't caused any permanent damage.

Pull the drain plug from the bottom of the case and drain the oil, if you find a lot of metal shavings, pull the rear cover and take a good look to see if you can spot where the metal is coming from, if the ring gear has deep grooves in the faces of the teeth, you will be looking at a complete tear down. If there is no real deep gouging of the teeth, it may be just a bearing going bad which you might be able to replace without a total rebuild, of course, you'll then have to figure out which one it is.

[Cliff. Elford]

Thank you a bunch for the ideas. The gears and teeth look good, no wear shows, no cracks. The oil was clean , no metal particles. I suppose the bearings are at the three points where the drive shafts meet. Right? Are there other bearings between those points? I do have an old repair manual that will answer those questions I suppose. Would changing all the bearings and seals be a job I can do in the garage or are there special tools needed to remove pressed on seals, bearings, and such? Where would these new bearings and seals be available?How about a torque wrench for reassembly? An absolute necessity? Once this thing is taken apart can a complete novice put it all back together again? Thanks. I appreciate your input.

[2ManyZs]

If you have never taken one apart and don't have the proper tools such as a torque wrench and a press, I would advise against it.

The rear pinion bearing is pressed on the pinion shaft, and the pre-loads need to be set correctly on the pinion shaft to get the proper contact at the ring gear. It does require some special tools, but you should be able to find someone to do it for you for a reasonable price.

I haven't done one myself as I don't have all the tools to do one right. If you do some checking with a local Z club or some of the racers in your area, they should be able to tell you of someone that can do it for a reasonable cost.

I believe you can get most of the bearings and seals from Victoria British out of their catalog. The only thing you might have to do is get the pinion shims from a Nissan dealer to set the preload on the pinion, if it requires shims other than the ones from the old diff.You should be able to get all the bearings and seals and shims you would need from someone like Courtesy Nissan, or perhaps even a local dealer. Of course, if all else fails, a Nissan dealer should be able to do the work, but it will likely cost a bit more.:disappoin

It is possible it could be in the thrust washers in the carrier that is causing the noise, but then, that is also something best left to someone who knows what they are doing.

Are you absolutely sure it is the diff that is causing the noise and not a U-joint or something else? Since you say there were not that many shavings in the diff, I'm wondering if it could have been caused by something other than the diff itself, like perhaps a U-joint, or a worn bushing causing excess movement in the diff mount or mustache bar?