Noise from trans or clutch or both?-video

[madkaw]

http://s2.beta.photobucket.com/user/_mad_kaw_/media/jimderk002.mp4.html

Might need decent speakers to hear this, but I'm just idling in the garage and depressing the clutch when you hear the noise change.Basically- depressing the clutch makes the noise go away. New clutch, PP, bearing, pilot bearing, tried adjusting slave unit and doesn't make a difference. So maybe trans input bearing? Car also makes a whine noise going down the road that only changes with speed-not gearing. I thought it might be the diff since they do have a reputation, but maybe this is all trans related.

[EuroDat]

I cant watch the video from my mobile.

I take it you have replaced those parts; clutch, pressure plate, thrust bearing, pilot bearing.

Did it have this noise before you changed the parts? What your describing sounds like the bearing between the input and output shaft in the transmission. In that case you should also hear it, maybe to a less degree, in 1st and 2nd gear. 4 th gear would be totally silent.

[madkaw]

Yes all parts are new and yes the noise was there before.

Need to drive it some more- just got it back on the road - let you know about fourth gear

[Zed Head]

I've had four used transmissions in my car and they all make the same bearing noise that goes away when the clutch pedal is pressed. The noise doesn't get worse over miles run though, and it seems to be just a noise, it doesn't affect operation. I've also read an account from one of the more experienced members here (can't remember who for sure) about rebuilding a transmission, installing it and having the noise come back within miles. The bearings used in these transmissions are C3 spec., which is a loose tolerance to allow debris to flush through. Maybe it's normal.

The later 71C transmissions, in the 300Zx and the 240SX, used sealed bearings which are probably tighter tolerance (haven't checked), maybe as an attempt to make them quieter.

[EuroDat]

The tolerances classes in ball bearings is an ISO spec. The internal clearances are classed from C1 (the tightest) through to C5 (the loosest or largest). There is also a CN and a CM. the The CN "normal" has a range sitting between C2 and C3. The CM "motor" is for electric motors and has a range similar to CN has has less noise.

Saying all that, the C3 spec is not the quietest ball bearing out there and will generate noise, but this was acceptable in those days.

I dont think the problem here is in the ball bearings. It is most likely in the neddle roller bearing between input & output shafts. The problem with replacing this bearing is the bearing is not the only thing that wears here. Its not a sealed unit and relies on the surfaces on the shaft to run properly.

If those two surfaces wear and become pitted it will be out of tolerance and make noise. Replacing the bearing will help but it wont take all the noise away.

Like Zed said, most of these transmissions make a degree of noise and that is normal considering the life on them. My Transmission makes noise and I am now planning the change over to a 300zx transmission type 71C.

Edited November 23, 2012 by EuroDat

[Zed Head]

Oops. Nomenclature fail on my part, clearance, not tolerance. Thanks for clearing it up, I can't tolerate mistakes on my part (pun :sick:).

I think that the "roughness" of the noise suggests the ball bearings instead of the needle bearings. At least for the noise I've noticed. It has a grindy bad bearing sound to it. If I recall correctly, there are only seven balls, of relatively large diameter compared to the needle bearings, in each bearing assembly. There are a lot of needle bearings in each cage.

In Post #4 above when I said "same bearing noise" I meant within the group of four transmissions. I couldn't hear anything in the video either. Anyway, might as well drive it and see if it gets worse.

Edited November 23, 2012 by Zed Head

[beermanpete]

It sounds subtle in the video. Unless it is much more significant than it seems in the video it is likely not a problem.

[EuroDat]

I have listerned to your video and cant make much of it. Doesnt make much differance anyway. If the noise is really annoying you then you need to replace ALL the bearings since the rest wont be far behind the suspect bearing. Identifying which bearing is not that important, just nice to know before you pull the tyransmission apart.

I used C2 bearings, but didnt help much. I think my transmission is just to old. Bearings are not the only things that wear in a tranmission.

I included a couple of photos of my tranny and the bearings. They are the old one out of the 71B. My next project will be the 71C transmission I have on standby.

Good luck with it

Chas

[madkaw]

I've had four used transmissions in my car and they all make the same bearing noise that goes away when the clutch pedal is pressed. The noise doesn't get worse over miles run though, and it seems to be just a noise, it doesn't affect operation. I've also read an account from one of the more experienced members here (can't remember who for sure) about rebuilding a transmission, installing it and having the noise come back within miles. The bearings used in these transmissions are C3 spec., which is a loose tolerance to allow debris to flush through. Maybe it's normal.

The later 71C transmissions, in the 300Zx and the 240SX, used sealed bearings which are probably tighter tolerance (haven't checked), maybe as an attempt to make them quieter.

Thanks for all the input guys. Glad to hear this isn't the only A trans that makes this noise. The problem is that the car is going to be going on the market soon and I am just trying to make sure it's mechanically sound. The noise is really prevelant at high idle-like when I first start the car and the choke has raised the idle. When idling at 700rpm, it is tough to hear.

I don't have a lot of miles on this car since it has just now getting road worthy. I will see if i notice any change in fourth gear. The other problem is that I believe the diff is noisy too-which is making it hard to differentiate between the two noises. Again, I need to get more miles on this car.

I imagine a lot of these issues are from the car not being driven enough. This 71 has 85k original. It probably sat close to 20 years wihout rolling anywhwere, which i would think caused dry spots on the bearing that led to rust. Not sure if some driving will help wear anything in or not. I have a spare r180 coming for the diff incase that is part of my issue. I think I better find a spare A trans.

[Zed Head]

Good point on general wear. More wear puts more load on the bearings as things get out of alignment.

Here's a thread on the 71C bell housing swap, just to round out the discussion. You can see the one sealed bearing in the picture on the second page. Probably not really a factor in noise.

http://home.comcast.net/~zheimsothtn/Transmission2.htm

[EuroDat]

If your planning to sell, have you tried new oil? Drive it for a while and get the oil warm, drop in over night. Fill it with a good quality oil and maybe an oil additive will help drop noise down to an aceptable level. Its less work than changing a transmission and you don't know what the other one will do. Yes that possible; Im speaking for a "been there done that" and now on my third transmission project, the 71c. Just working my way through the alfabeat, abc...

Goodluck

Chas

[madkaw]

Drove the car around some today and your statement seems to hold true about fourth gear-it does get quiet. So where does that leave me as far as fixes? Since the car will be up for sale, I would think most prospective buyers would be leary of the noise-it is pretty loud. The trans seems to function just fine though.

Sounds like trying to find a replacement A trans will just be more of the same from what you guys are saying.

It also sounds like a rebuild won't fix this-really?

I cant watch the video from my mobile.

I take it you have replaced those parts; clutch, pressure plate, thrust bearing, pilot bearing.

Did it have this noise before you changed the parts? What your describing sounds like the bearing between the input and output shaft in the transmission. In that case you should also hear it, maybe to a less degree, in 1st and 2nd gear. 4 th gear would be totally silent.