FS5W71B 280zx transmisson rebuild

[EuroDat]

Hi Dave,

Looking at the third gear rotating in the video. It's not good. Some not right with it and the noise is gone with it out, seems to indicate that 3rd gear is your culprit.

Tip for mounting the front counter shaft gear. Put in in the oven for 30 minutes at 60°C. It will go on a lot easier. Works well with bearings too.

General rule with press fit items is not to do it too often because they can loosen and loose there grip on the shaft.

 

[Zed Head]

I'm tempted to try and pry the synchro cone off of a gear just to see if I can.

[Dave WM]

I was shocked at how little force it took to square up that gear gap. I have a carpeted (thin) garage (less likely to chip things that way) I work in, maybe I dropped it and hit just right to mess up the gap, I don't remember doing that but can't say for sure. anyway will know soon enough, I will have it back together tonight to see.

[Dave WM]

1 minute ago, Zed Head said:

I'm tempted to try and pry the synchro cone off of a gear just to see if I can.

maybe the bevel edge of a bearing puller..

[Dave WM]

I installed the 3rd gear and before putting on the sycro hub I checked with a dial indicator, very good, finished installing the hub, counter shaft gear and input shaft, test spin by hand, no perceivable wobble. Just have to reinstall the front bearings before I can put back in bell for testing.

 

oops, forgot the input shaft bearing needs to be installed BEFORE installing the input shaft/counter shaft gear, duh... I think that is the most fiddly bit about this job juggling the input shaft, brass sync ring and pressing on the counter shaft front gear all a the same time. I think I can see why the village land guy installs the countershaft with the front gear already on, he just meshes the two shafts while inserting them both into the adapter plate at the same time, not the way the FSM shows it.

Edited November 1, 2017 by Dave WM

[Zed Head]

I just looked at my 4th gear (the one on the input shaft) and 5th gear and the "engagement ring" (been Googling, proper name) on those two is pressed tight against the gear.  3rd has the .014" gap.  I wonder if it's coming apart.  If you get yours to work I might give mine a little tapping with a hammer to see what's what.  Did the gap close up tight on yours or just even up?

[Dave WM]

just evened it up. Maybe it could be closed up all the way. Its running perfectly true now, but I still have the noise, not as bad as before but its there, going to have to play with it some more.

its getting to the point where I am starting to be discouraged by it. It seems to only be there when the front bell housing is on. If I leave the rear housing on it gone. I must still have something not running true, and the bell housing amplifies it like a resonating horn.

The problem is since I cant reproduce it with the bell on, I have to look with it off and see if I can find something that could make the problem.

I am almost to the point of just installing it and taking for a test ride. It would take less time that constantly assemble and disassemble. I still have the other one that does not have any of the same kind of noise, so that one will be installed if the test ride is a failure.

[Zed Head]

The front case locks down the other end of the shafts.  Clues seem to point to a bent shaft.

[Dave WM]

here is the latest, I can engage 3rd gear and the bump sound takes places on the output shaft in exactly the same place every rotation (rear housing off bell on). I have examined the teeth of the 3rd and the counter shaft 3rd, can see nothing. the bump does NOT take place on the staked nut every rotation on the other gears engaged (moves around faster or slower on staked nut). The problem is when the case is off I get no bump even from 3rd. maybe the gears are not tightly meshed with out the cases, enough to mask a problem with 3rd (assuming that is it).

as to bent shafts, the main shaft can be held still and it still bumps, so that should clear that one. the input shaft does not have single rotation bump, the only constant that relates time wise to the bump is an engaged 3rd gear. I can't see how the counter shaft could be bent. I presume if its the gear then it would be a single tooth so I have to mark the exact mesh point and get a much closer look. I was thinking the sliders but if they were the problem then the bump would take place on the same point along the output shaft regardless of which gear. And when the 3rd gear was removed it did not bump.

will take a closer look at the 3rd and the counter shaft (boy if that is f'd then its hopeless) tomorrow when I have better light.

I may pop for a new 3rd if I can get one from japan, that you had looked to far gone (at lest the engagement teeth did). That is IF I can find damage on the gear.

 

Edited November 2, 2017 by Dave WM

[EuroDat]

I agree. I think 3rd gear needs replacing. I can't recall ever having seen one of these gears seperating (wobble) like that. The fact that you can press it "true" again without too much effort, doesn't seem right to me. Then again I have never had one wobble and need to try that.

[Dave WM]

ZH I would like to try that bunged up 3rd you have, I could at least confirm its the gear for sure that way. If I get the exact same noise then I could assume its the 3rd counter shaft an not the output shaft gear. I hope to get it under the mag glass today to get a much closer look. I am going to mark the counter shaft where the noise occurs as well. If another gear results in the noise at that same spot on the CS gear, then it would follow the CS gear is bad.

I am going to start by spraying some carb cleaner right at the spot I think the issue is, that way I can get a better look without any residual oil hiding any defect. I can tell you from a cursory look its not obvious.

Edited November 2, 2017 by Dave WM

[Dave WM]

added more videos of the fixed wobble. took a closer look and I can see some minor chipping damage right in the middle of the gear teeth exactly where they mesh that corresponds to the noise. I mean its MINOR right in the middle with near where the relief cut is made in the gear (the one that circles the entire gear). All the rest of the teeth look flat, there is a tiny divot on two of the teeth. I am finding it hard to imagine they could cause the noise, but it seems they are the only suspect.

I am thinking of removing the gear and using a dremal moto tool to see if I can smooth that area out. Not sure I can do it with the gear installed, even though that would greatly reduce the effort. maybe with one of the thin grinding stones I could get in there. I would hate to take it apart and put back together again to find no change after working the gear. I will try to get a close up pic of the damage later today.

pt1 of the wobble shows me using a dial indicator to check the cone.

Edited November 2, 2017 by Dave WM