Datsun Roadster Forum-311s.org

Again, did your 5th work if you held it in place? If so, it is most likely the detents. Did your 5th act like neutral? if so you have a non-splined 5th, or a backed off nut. I hope you have a missing spring, or mismatch on your deternts.much cheaper. Pat Sorry, it sounds like your detent spring/ball are incorrect. That is the best news for you. I can assure you that when 5th fails, it is not pleasant. Take out your springs and balls, and verify they were put in in the correct order

That sounds like the best news. figure out your balls/ springs, and change your throw out bearing. Pat

Also, find someone local, to take a look. It's no fun to pull the motor/trans. Pat

Check out the attached photos guys. It looks like the thrust washer is installed backwards. Could the preload be messed up and thus the nominal trans vibration and separation forces be causing the 5th to pop out?

Not sure what the effect would have other than not spreading the torqueing clamping force other than intended. Regardless, it's a pretty bone-headed and careless assembly.

FWIW....It looks backwards to me, compared to my rebuild....I can't weigh in what issues may occur, from being installed backwards, though,...I'm no expert in that regard.
Best of luck to you, I'm rooting for your success !
Mike

Quick question: are the mainshaft nuts left-handed? Apparently, on the z's they were left-handed.

Thanks!

I am pretty sure they are not left handed threads.

Look at the 5th speed gear splines are they parallel to the output shaft or worn / tapered
The syncro sleeve tapered too or have a bit of stress cracks inside both will allow or help it kick out

We used to get irate customers wanting the manual trans like new ....we and a lot of dealers told them buy new $4000 ....$1600 then
Shafts get warped... gears angle a fraction instead of perpendicular, ....cases tweaked ,worn wrong # parts
Used
my recommendation a new 5th gear and full syncro

Thrust washer is definitely backwards.

Also there is a ball bearing that sits in a divot on the main shaft. The thrust washer has a slot the picks up the ball locking it in place. It may be that the torque from the gear causes it to pop out because washer is not properly located and locked.

PM me with you phone # if you want to talk. There is a lot to say and 311s times out before I can type it.

Wrench is 38mm, you can buy a 38mm crows foot 1/2 drive on Amazon fairly cheaply.

Here are pics of my crowfoots

Thanks Joe!

I have posted yet because I was waiting on my amazon crowsfoot and needed some snap ring pliers.

Question: should there be any axial play in the 5th gear itself, i.e., be able to move up and down? I have some slight movement in mine, slight = 0.010".

I would say no to any play.

Per manual main shaft gears have end play of 0.1 to 0.2mm

Page 138 of U20 and 5 speed service manual in the tech wiki

I agree with Joe, that washer should be reversed. If you already stated that 5th gear is fine if you hold it in, then you should be looking at your detents, not the play in the gear. I think you said that you've already had a welded 5th put in, so it wouldn't be slipping. If a shop can put a thrust washer in backwards, they could have messed up the balls/springs. Easy check, cheap parts. Make sure your linkage rod springs are in correctly,that affects gating into 5th also. Pat

the stiffer spring goes on the passenger side of your shift rods. Here is 2 for reference. Pat