Transmission Noise in 3rd Gear - F4W71A

[AnvilZ]

@Zed Head I was wondering about that, I included it in the video because it didn't seem right especially since that allows the constant mesh gears to become slightly misaligned. While we wait for some feedback from the others you tagged do you have any insight into my second question around the FS5W71A kit for the 280Z and whether that will work as a rebuild kit for my transmission?

Assuming it is a bearing issue I would think it is a good time to replace all the bearings in case any of the others are close to going out. I could get a rebuild kit on order in the meantime. 

[EuroDat]

Hi AnvilZ,

The movement you show in the video is not a problem. It is normal for the input shaft to move back and forth like that once it is removed from the transmission case.

The input shaft is actually held in position by a outer circlip on the bearing. You removed the circlip to dismantle the transmission.

The main (output) shaft should not move like that. If it does, then your centre bearing in the adapter plate has collapsed. 

The bearing kit for the FS5W71B will not work on the F4W71A. Different bearings.

I have the bearing numbers somewhere, but it has been 7 or 8 years ago since I last needed them. I will see if I can find them for you. You can also dismantle the transmission and take the bearings to a local bearing supplier. They are common bearings.

[EuroDat]

I now have read through this thread and what you are describing sounds like a failed neddle bearing between the input shaft and the main shaft. 3rd gear puts the most strain on that needle bearing. If it starts giving problems, then 3rd will show it first.

It will be interesting to see what the bearing looks like.

Edited July 29, 2021 by EuroDat
Added screenshot

[AnvilZ]

EuroDat, thanks for the feedback, that makes sense about the input shaft being held in by the circlip. The main shaft is not moving at all so I assume my adapter plate bearings are still in tact. 

1 hour ago, EuroDat said:

The bearing kit for the FS5W71B will not work on the F4W71A. Different bearings.

Out of curiosity did the 280Z come with the FS5W71A transmission as well or was that only on the 2000 Roadster? Maybe this is a typo on drivetrain.com? Their website shows that transmission in the 280Z/ZX among others: 

If you are able to find the bearing part numbers that would be very helpful, I will get to work on removing that needle bearing in the meantime and post a picture of the condition once I have it. 

 

Edited July 29, 2021 by AnvilZ

[madkaw]

I can't help much with gear boxes except to say that sending the tailshaft to Australia  and getting rid of the monkey motion was the best thing that ever could happen to the A box. I couldn't believe the difference and how precise the shifts were. The owner was over the moon with the rebuild. 

Lou Mondello is the man. He has a machinist that makes the magic striker rod .  

[Zed Head]

2 hours ago, AnvilZ said:

Maybe this is a typo on drivetrain.com?

There is bad information out there on the various web sites about the Z car transmissions.  And the kits are incomplete.

Here is where EuroDat got that drawing.  Compare the part numbers and you might be able to confirm that it's the same bearing used in the later four and five speeds.  Then use EuroDats's writeup to cross-reference.

Click through the four speed page and you'll find the early 4 speed.  You can probably find a cross-reference to the Nissan part number also.

http://www.carpartsmanual.com/datsun/Z-1969-1978/power-train/transmission-gears

 

[Dave WM]

the mesh is also maintained by the counter shaft shims in the front cover that act on the outer race of the front counter shaft bearing.

Edited July 30, 2021 by Dave WM

[AnvilZ]

I noticed when I disassembled the transmission that there was a shim on the larger main input shaft but not the smaller counter shaft. It does look like the transmission may have been rebuilt before, if the shim was not replaced on the countershaft could that have caused premature wear and failure?

[Dave WM]

1 hour ago, AnvilZ said:

I noticed when I disassembled the transmission that there was a shim on the larger main input shaft but not the smaller counter shaft. It does look like the transmission may have been rebuilt before, if the shim was not replaced on the countershaft could that have caused premature wear and failure?

double check the front cover. The shim will tend to stick to that on the counter shaft bearing recess. Its easy to not notice it, and if that happens its easy for it to eventually get lost as the cover picked up and moved around. The oil is pretty sticky but eventually it will fall out.

I assume its there to maintain the proper mesh of the gears, if the gears get too far out of mesh they start rubbing into the hubs, it will make an awful sound, you can see this by just moving the shafts out of alignment.

I don't know if the tiny bit of miss alignment cause by a missing shim (there are different thickness shims out there I assume for production tolerance compensation.

You need to follow the FSM and use a micrometer to see if you need one and what the thickness should be.

 

[AnvilZ]

@EuroDat I attached a video of the needle bearing you mentioned between the main input and output shafts. It looks in good condition to me, maybe I should plan to replace all the bearings while I have it apart anyway just to be sure. Any other thoughts on what could cause the issues in 3rd gear?

[EuroDat]

13 hours ago, AnvilZ said:

@EuroDat I attached a video of the needle bearing you mentioned between the main input and output shafts. It looks in good condition to me, maybe I should plan to replace all the bearings while I have it apart anyway just to be sure. Any other thoughts on what could cause the issues in 3rd gear?

IMG_6370.MOV

The bearing is ok. Your problem is elsewhere and now to find it.

[EuroDat]

I have some questions and test, but now the transmission is out and dismantle, I hope you can varify some.

1. Was there enough clearance between the tunnel and monkey motion when in third gear? Sometimes the selector stick can hit the bodywork, mostly after some kind of modification.

2. If you held the gearstick, did the sound change in tone, reduce or stop?

3. Was it always in third through the whole rev range? Yes the frequency will increase with revs, but did the cluck maintain the same? Clunking at 1500rpm was dubbled at 3000rpm.

4. Was the clunk during full acceleration, coasting and de-acceleration? Did it change ?