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Transmission Noise in 3rd Gear - F4W71A


AnvilZ

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Hi all, new to the forum so hopefully I am posting in the correct location but hoping someone can help with a transmission issue. I am nearing the end of a complete teardown and rebuild of my 5/71 240Z with the Monkey motion F4W71A trans. Finally got the car mostly back together and running, but I am getting an awful clunking sound from what sounds like the transmission that only happens in 3rd gear. 1st, 2nd and 4th all seem relatively quiet, I have maybe noticed a slight noise in reverse. Maybe not surprising considering the car has been sitting for the better part of 15 years prior to the rebuild. Anyway, I do not notice any grinding or trouble shifting for any of the gears, or any noise or vibration in neutral. Assume this is maybe a bad bearing or potentially a problem with the gear itself? Anyone experienced a similar issue?

I was not able to get a good sound clip, however I did pull the transmission yesterday and plan on rebuilding it myself, which brings me to my other question on the rebuild kits. It sounds like the parts are expensive/hard to come by for the A type boxes, I did find a bearing kit (https://www.datsunparts.com/1049)  that says it is for both the F4W71A AND FS5W71A that was apparently the 5 speed used in the 2000 Roadster? Is this the same FS5W71A used in the 280Z, and if so would a kit like the one here https://www.drivetrain.com/nissan-fs5w71-synchro-kit-07-nissan-fs5w71-synchro-kit-dts-bk104 work for the F4W71A? If that is the case the parts seem readily available and fairly cheap from drivetrain.com, but maybe I am missing something. 

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I will check that, thanks for the suggestion. Would that manifest more when shifting into 3rd or once the transmission is already in gear? Or both? To add some clarification that clunking sound is continual while in third regardless of speed from what I can tell. Actually shifting into 3rd seems pretty smooth, just as soon as I let out the clutch it starts clunking.   

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3 hours ago, AnvilZ said:

awful clunking sound

 

36 minutes ago, AnvilZ said:

To add some clarification that clunking sound is continual while in third regardless of speed from what I can tell.

Can you add some detail?  Are you saying that the clunking rate is constant despite RPM?  How can that be?  Does it continue to clunk if you're in 3rd with the clutch pedal down, car not moving?  Or does it only happen when the car is rolling?  Clunk is not very descriptive, even with the awful added.

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Sorry I see how that is confusing, I meant to say that it is continual throughout 3rd gear at any speed. The frequency is definitely speed dependent though, it would increase with RPM. It does not clunk with the clutch pedal down in 3rd. I don't know how to describe it other than a clunk, maybe there is a bit of grinding going on as well that I cannot hear over the engine noise. Definitely not a whining sound though. 

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From what I can tell it is about the same under acceleration and deceleration. I had also considered that maybe it was something to do with the harmonics of the drivetrain, maybe something in the propeller shaft/diff/half shafts but it stops as soon as I shift to second or fourth.

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Sounds like something on/in the coupling sleeve and hub gears.  Could be a chunk stuck in the teeth or a broken tooth.  The shafts and main bearings are all shared between and the gears themselves are constantly meshed so a gear problem should be heard all the time.  Only the coupling sleeve and hub meshes when you select a new gear.  Although, there is a needle bearing under each gear that might deflect under load.

Others have more transmission experience.  Seems like you'll need to take it out and apart though to know for sure.

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On further thought I'm not sure about my post above.  The sleeve and hub mate around the full circumference, the gear teeth mesh at a single point around the circumference.  So a noise that changes with RPM would have to be related to the mesh point of the gears.  I think.

Anyway.  Another quick way to get a look is to drain the fluid.  The stuff that comes out will tell a story.  Looks like you must have drained it, was there anything there?

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@Zed Head I drained the original fluid a while back and didn't pay much attention to it, now I wish I had. I did replace it with Redline MT-90 during the rebuild and when I drained that yesterday I didnt see any metal shavings or chunks in that or on the magnetic drain plug. Although I have only put a few miles on the car due to the issue with the transmission since I got it running again. 

@Mark Maras good question, I did not check that before pulling the transmission.

Just got it torn down though, here is a video with it in 3rd gear. No chipped teeth or issues with the synchros that I can see on visual inspection but I am no expert. 

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@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. 

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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.

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Posted (edited)

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.

Screenshot_20210729-232813.jpg

Edited by EuroDat
Added screenshot
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Posted (edited)

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: 

2021-07-29 18_09_35-FS5W71 Nissan Manual Transmission Rebuild Kits and Parts - drivetrain.com.png

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 by AnvilZ
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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 .  

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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

 

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Posted (edited)

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 by Dave WM
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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?

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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.

 

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@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?

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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.

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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 ?

 

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3 hours ago, EuroDat said:

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 ?

 

1. Yes, there was clearance with the shifter and the transmission tunnel. There were no modifications, original engine and transmission is still being used with the original mounts. 

2. I did not specifically test this, however I don't recall any changes when holding the gearstick. 

3. It seemed to be through the whole rev range, I didn't notice it getting significantly louder at higher RPM though, mainly just a proportional increase in frequency with RPM. 

4. I did not notice a change between acceleration/coasting/deceleration. I should have spent more time on this to note differences, but I only put a few miles on the car with the issue for fear of causing further damage. The noise seemed bad enough that I was worried I would cause significant damage if I kept driving it. 

Hopefully this helps, sorry I cannot offer more detailed data now that I have pulled the transmission. I believe I mentioned it already but I did also notice a slight clunk and maybe a bit of grinding in reverse as well. Nowhere near what it was in 3rd, but still enough to notice. 

I have been hunting down bearings, I have ordered the two larger main shaft bearings and I am searching for the two smaller counter shaft bearings. I may replace the main needle bearing as well just to be sure. From the diagram you posted above it looks like there is another needle bearing on the main shaft that 3rd gear rides on, #34. Could that be causing similar issues?

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