Transmission output shaft nut

[Geep]

While tracking an issue of my ‘76 ‘02 slipping out of second gear, I noticed the nut securing the yoke to the transmission output shaft was loose. There was a little (couple mms) of in-out play here. Could this contribute to gear slip-out, and what is the proper way to install this nut locking plate (?) between the rubber coupling (guibo?) and the output shaft?

[Son of Marty]

After the nut is torqued down the lock plate surrounds the nut and you'll see a small divot on the flange, in your picture it looks like it's at the 12 o'clock position, with a punch bend the edge of the lock plate into the divot.

Edited May 11 by Son of Marty

[Preyupy]

Or just use LocTite on the nut and don’t worry about the lock plate.  As you can see if the nut starts to come loose the lock plate does very little to hold it in place.  Before you torque it all down check the play in the splines between the output flange and the main shaft.  If it has been running loose for a while they may be beat up.  
 

If they are this may not be the 1st time this has happened. If there is play you may have a problem with the nut coming loose again even with LocTite & the lock plate. 
 

And yes if the nut was loose and had backed off from the output flange it would allow the main shaft to move forward and backwards as you get on and off the throttle and this could cause it to jump out of 2nd gear.  

[stephers]

I would think about replacing that shifter seal as well, looks like it is leaking quite a bit       You have a 76 so it is the fine splined shaft which is not so prone to wearing out the splines but it can happen.    I would also think about replacing the output shaft seal as well

 

Thanks, Rick