Transmission Noise in 3rd Gear - F4W71A

[AnvilZ]

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?

[AnvilZ]

I finished disassembly of the main shaft, all the individual gear needle bearings look to be in good shape. Even wear patterns on the collars that they ride on as well. From what I can tell the collars that my arrows point to for 3rd and 4th are part of the main shaft and there is no ball bearing under those collars like the one under 2nd? (I removed that small ball bearing, not pictured but it was in place). 

[EuroDat]

It looks like it is an issue with the third gear. Its you have no end play in the main shaft it is not the ball bearing in the adapter plate. The needle bearing between the input shaft and main shaft shows some wear, but it's not causing any problems.

I'm not and expert on the 71A transmissions, but most of the components are very similar to the 71B used in the 720 trucks and the later Zeds.

The next step I would take is to dismantle third gear. You will need to remove the cluster shaft front bearing and front gear, which is held on with a circlip, to be able to remove the input shaft.

Pay particular attention to damage around the circlip holding the 3rd/4th gear hub on the main shaft. I have only seen it happen once, but the circlip came off and the hub could move back and forth. That made some serious clunking sounds only in third. It was also making some much quieter noises in 1st and 2nd. That happened after a guy did a home rebuild and when it started clunking he bought it in to have checked.

I wouldn't expect this from the factory, but these cars are old and many repairs later....

The 3rd/4th hub and sleve are pos 4,5 and 6. The gear pos 16 needs to be removed from the cluster shaft pos 17 to remove the input shaft pos 2.

[EuroDat]

16 minutes ago, AnvilZ said:

I finished disassembly of the main shaft, all the individual gear needle bearings look to be in good shape. Even wear patterns on the collars that they ride on as well. From what I can tell the collars that my arrows point to for 3rd and 4th are part of the main shaft and there is no ball bearing under those collars like the one under 2nd? (I removed that small ball bearing, not pictured but it was in place). 

The needle bearings in the gears look good. That dull colour on the shaft is slight wear, but not excessive damage. It's normal.

The are actually 3rd, 2nd and 1st. 4th is a direct drive through to the input shaft and doesn't have any reduction though the cluster shaft.

The photo looks like the 3rd gear needle (left side row) shows signs of blueing which could be a sign of excessive heat build up.

Are all the hub, sleeve and shifting inserts ok?

How was the circlip holding the 3rd/4th hub? And the end clearance to the circlip?

[AnvilZ]

30 minutes ago, EuroDat said:

The are actually 3rd, 2nd and 1st. 4th is a direct drive through to the input shaft and doesn't have any reduction though the cluster shaft.

Yes, that is my mistake. The 3rd gear needle bearing is not blueing, just the lighting in the picture. No discoloration on the left side row. 

The circlip was in place and tight, no damage that I could see. The 3rd gear assembly looks ok to me as well.

The only thing I notice on the hub is some wear on the 4th gear side where the 4th gear synchro rides. I circled it in the picture but there are two dents or chips there, the 3rd gear side looks much better. I assume the wear around the inner diameter is from the circlip, is that normal?

 

You can actually see one of the dents/chips I mentioned in the assembly picture above as well, on the right side of the hub. 

Edited July 31, 2021 by AnvilZ

[EuroDat]

2 hours ago, AnvilZ said:

The only thing I notice on the hub is some wear on the 4th gear side where the 4th gear synchro rides.

Those marks are only wear marks from the circlips. That is most probably why they changed the design to springs under the shifting inserts in the B version. I don't see any serious issues in the photos.

The way the syncho works is simple. This is a basic description of how they work. The shifting inserts are pushed into the outer hub by the circlip or springs. The outer hub is held in the correct position by the selector and selector detent ball/spring. The shifting inserts insert into the three tabs cut outs in the synchro ring and lock it with the hub. The synchros turn with the hub. When the sleeve moves toward a gear it pushes the shifting inserts and the synchro onto the cone of the gear. When pressure is applied the synchro will speed up or slow down the gear until its rotating at the same speed. When more pressure is applied the sleeve slips over the hump on the inserts and engages the gear. Its held in gear by the selector detent ball/spring.

Looking at your photos. The hub, circlips and gear needle bearings look ok. Makes me wonder if you were not experiencing a frequency vibration that was worse in third gear and causing a rear engine mount to tap against too long mounting bolts for example. I'm not saying that is your problem, but it could be something outside the transmission.

[AnvilZ]

5 minutes ago, EuroDat said:

Looking at your photos. The hub, circlips and gear needle bearings look ok. Makes me wonder if you were not experiencing a frequency vibration that was worse in third gear and causing a rear engine mount to tap against too long mounting bolts for example. I'm not saying that is your problem, but it could be something outside the transmission.

I wondered about this as well, however I may have found one of my issues. When I pressed the larger main shaft bearing out of the adapter plate and inspected it further it does not spin smoothly. It chatters a little bit and seems like it may be going out. I am wondering if under load in 3rd gear it causes the excess vibration. You mentioned 3rd puts the most load on the main shaft correct?

[Dave WM]

iirc the forward most servo hub is directional, unlike the others. not sure but i think is possible to go in the wrong way. I dont know if this could cause the clunk issue, but i would recommend you look at it very closely and check the fsm. I think it mentions this. 

[AnvilZ]

Good to know, thanks for the suggestion. I will triple check the hub orientation during reassembly. 

[AnvilZ]

7 minutes ago, Dave WM said:

iirc the forward most servo hub is directional, unlike the others. not sure but i think is possible to go in the wrong way. I dont know if this could cause the clunk issue, but i would recommend you look at it very closely and check the fsm. I think it mentions this. 

I should also ask, do you know if this applies to both the A and B transmissions? I downloaded my copy of the FSM from Xenonzcar but the 72 version was the earliest available and I would assume it covers the F4W71B. Is there a 1971 FSM floating around somewhere?

[Zed Head]

On 7/28/2021 at 10:31 AM, AnvilZ said:

The frequency is definitely speed dependent though, it would increase with RPM. It does not clunk with the clutch pedal down in 3rd.

Have you checked the action  of the shift fork on the coupling sleeve, and the sleeve on the hub?  I wonder if the sleeve could get cokced on the hub as the fork pushes it over.  Like if one tine of the fork was ahead of the other.  The sleeve should lock in, or center over its final position, but maybe you're getting incomplete travel and final engagement.  You have it all torn donw now but you might find some sign on the parts.  Maybe a loose fork on the rod.  The roll pins do fail.  Ideally, you would check the action by moving the shift rods with it mostly assembled.  There are also the detent pieces in the adapter plate.  The balls, springs, and pins that set the final position of the shift rods after a gear selection.

Your description sounds like something relatively large wobbling around the shaft.  If all of the bearings and other parts seem undamaged and correct then it seems like the parts must not be correctly positioned.

[EuroDat]

13 minutes ago, AnvilZ said:

I should also ask, do you know if this applies to both the A and B transmissions? I downloaded my copy of the FSM from Xenonzcar but the 72 version was the earliest available and I would assume it covers the F4W71B. Is there a 1971 FSM floating around somewhere?

Xenonzcar doesn't have the 71A. I don't know where you can find one these days. They were available, but I never downloaddd it. You are one of the thew that wants to rebuild a F4W71A.

I'm no an 71A expert, but I think the sleeves and selector forks are interchangable and the sleeves reversable on the 71A. That is not the case with the 71B.