wide ratio FS5W71B slipping out of 3rd & 4th

[Zed Head]

I think it's a countershaft issue.  4th gear is direct through the main shaft.  Not sure what exactly it might be or what to do about it.

[Jeff Berk]

Good point on the countershaft. I didn't know 4th was a direct drive.

If it's an issue with one of the three countershaft bearings, is there a way to test them? They were all replaced so they should be fine but I installed and removed parts so often to fix errors, maybe I damaged one. Other than that should I check to see if gears are not properly matching? 

One issue I had with the countershaft was that I was unable to remove the countershaft drive gear.  This required that I remove both the main and countershaft at the same time. After its removal, I tried a gear puller and an ultrasonic cleaner, but it wouldn't budge. I wonder if I moved the drive gear outward a little on the countershaft.

There is a potential that I mixed up a couple of gears between the 3 transmissions I had open although I tried to keep them separate. The tooth count on the shafts are as follows from front to back:

Main shaft

22, 28, 28, 33, [adapter plate],  36, and 19

Countershaft

29, 27, 19, 14, [adapter plate], 23, and 31

 

[Jeff Berk]

Zed Head

I just found this in my search:

It agrees with your thoughts on the root cause of the noise. I have to admit that I dropped the transmission onto a rubber mat when I was trying to fit it into my vice. If it landed on the countershaft, that could of damaged the bearing. 

[Zed Head]

Those guys from 2003 seem pretty cool.  The rear countershaft bearing would be the one in the adapter plate.  

Just looking at the picture of the gears you can see so many spots where that high frequency buzz could happen.  Gear teeth touching slightly maybe.  Gears slightly out of alignment.  It doesn't sound like a tooth count problem, that would be a major problem.

The fact that it happens when the countershaft is loaded suggests that the helical cuts of the gears are pushing two parts together, or one of the shafts is loose and being pushed away from the other.  So something is slightly misaligned, or loose.  When the countershaft isn't loaded the gears are just along for the ride.  No noise then suggests they are moving just fine, it's the load that makes the difference.

It's a bummer.  I'd drop the oil and see if metal flakes show damage happening.  It will give you a clue at least.

[mayolives]

I suspect that It would take a lot to damage it by dropping it on a rubber mat, but I agree that your problem could be located at the countershaft.  Also, if you installed gears from different transmissions, this could easily cause a whine due to wear patterns not being the same.  Could the gears "wear in" with more use?  It's difficult to judge just how loud your whine is from the video due to not having the console in place, etc.  I have a G-force gear box in one of my cars that really whines and sings all the time so I'm kind of numb to the noise.  How much have you driven your car and has the whine sound changed, louder or less loud during test drives?       

[Zed Head]

1 hour ago, mayolives said:

Also, if you installed gears from different transmissions, this could easily cause a whine due to wear patterns not being the same.  Could the gears "wear in" with more use? 

This seems reasonable.  See if it makes more or less noise if you use the gears to decelerate.  More clues.

My 78 5 speed used to make whining/whistling noise when I got on it at high RPM.  Sounded kind of neat.

[Jeff Berk]

I only drove it a few minutes due to concern about the whine. I'm think that by dropping the transmission, if it landed on a countershaft end, damage the center countershaft bearing is reasonable. Next time I'll have my son tighten the vice while I'm holding the transmission while holding the aluminum vice jaws. I just ordered a replacement center bearing. I'll attempt to replace it without disturbing the main shaft.

I'll drive it a few more times to see if I can get a little more information. 

Before starting this project, I purchased a transmission adapter for my jack. This really makes removing and installing the transmission relatively easy. I'm finding the hardest part is getting the four screws holding the drive shaft to the differential the hardest part. I gave up on using a torque wrench and had to borrow a crowfoot wrench to get to the differential side of the coupling. Does anyone have a suggestion?

[Zed Head]

Set your wrench up on the nut, using the tunnel to brace against, and use a big screwdriver through the u-joint yoke to turn the propeller shaft instead of the nut.  

Hopefully you have the D-head screws, that lock against the yoke by themselves.  You only need a wrench for the nuts.

[Jeff Berk]

PXL_20210426_183301294.mp3I took it out for a slightly longer drive and recorded the sound in 2nd gear with acceleration and then deceleration. I've attached the audio file. 

I also noticed that it is slipping out of 5th when I let up on the gas so I'm assuming that means it's not being pushed fully into 5th gear. 

If all else fails, I have a 4-speed of unknown condition I could try. PXL_20210426_183301294.mp3

[Zed Head]

Your audios didn't load.  Have you seen the posts about the shifter interfering with the transmission in 5th gear?

https://www.classiczcars.com/forums/topic/57424-280z-5th-gear-synchros-gone-bad/

https://www.google.com/search?q=5th+gear+siteunseen+shifter+site%3Aclassiczcars.com&rlz=1C1SQJL_enUS862US862&sxsrf=ALeKk02iQ-qp-Kb_POtLeZmJ-1z6Vac4pQ%3A1619467480443&ei=2ByHYP-yGqWT0PEPut-kEA&oq=5th+gear+siteunseen+shifter+site%3Aclassiczcars.com&gs_lcp=Cgdnd3Mtd2l6EAM6BwgAEEcQsAM6BwghEAoQoAFQ9BtYwGFg1GVoBHACeACAAaEBiAGwEJIBBDIwLjaYAQCgAQGqAQdnd3Mtd2l6yAEIwAEB&sclient=gws-wiz&ved=0ahUKEwj__pW_2pzwAhWlCTQIHbovCQIQ4dUDCA4&uact=5

Edited April 26, 2021 by Zed Head