Datsun Roadster Forum-311s.org

5th gear— to weld or not to weld? To double nut of not?

So, it was a great start to the week. I cracked into my transmission today with the invaluable help from Andy.

It seems to be mostly very very good news.

It had obviously been rebuilt and everything looks really really good.

No issues.

It has a splined 5th gear.

Warner. Brass synchros. A ‘True’ Warner from what I have been told based on the fact that it has E clips on 1-2, 3-4 shifter rod/rails??? However? It only had one main shaft nut, and I have been told that ‘true’ Warners always had two nuts???

Questions:

Considering that it is a splined 5th—

Do I need to weld or tack anything?

Do I need to add another nut?

I have only tomorrow to finish this so any quick advice is very much appreciated.

Thank you!

Peter

If it is splined my understanding is there is no need to make any modifications. If there is room to double nut, I can’t see how that would hurt anything, but I am no expert! I did double nut mine when I did it.

I sent my un-splined 5th gear to Dean, where his guy, Mark Degroff performed his welding and honing services on it.
I torqued the double nuts on my Servo 5-Speed in strict accordance to the procedure and torque values specified in the Clymer Service Manual, and Scott Scheeler's book. I also used a new "folded tab" locking washer because that's what was there originally, when I first took the tranny apart.

Lastly, ....I put a couple of tack welds around the two nuts, that could be easily filed, or ground down, should I ever have to take it all apart again....and here is where the heated debates, and hostile insults started to come my way ....hopefully, that won't repeat itself....
See photo for reference...

Thank you guys so much!

Dave Premo has been so helpful tolerating all of my questions... and he just confirmed a little tack weld on the nut to threads.

I’ve been trying not to bug him too much, so I asked here and really appreciate the advice and confirmation.

Thank you!

Unless I've misunderstood your statement, I'm not sure a weld on the threads is a good idea, wouldn't that bugger up the threads for future use ? I placed my tack welds on the seam between, and only on the flats, of the two nuts themselves, after they were BOTH PROPERLY torqued against each other......but that's all I'll say,....I know Dave is well respected, and I can only wish I could know him, and use his experience.
Respectfully, Mike

Yeah it does ruin threads you can't use them again or Datsun trans techs used thread locker after a acid wash in addition to the nut collar detented or double nut
Occasionally they had trouble with the nut loosening and even tach welding failed they determined the customer was dogging it in 5th ( he did on test drive ) and it caused a vibration that caused it to fail

If you tack on the threads it will cock the nut most times causing the nut to only tighten cocked ...if up on the shank and collar then no problem
But the forged case hardened shaft is turned back to mild steel in those welds , our trans tech thought the replacement nut from Nissan wasn't as good as the factory one causing probs

It DOES NOT hurt it is just one tack weld at the nut. Please listen when I say this is the safest thing you can do to keep the nut from backing off, I have been many years and have taken them apart successfully by just grinding off the little tack weld.
Dave

Oh boy, many approaches, each of which sound like they make perfect sense to me. I’m still considering all options.

The tack to the threads does sound potentially ‘destructive’, however if one has to get that nut off in the future and you only grind off a small tack, that’s a tiny fraction of the the threads - 1-2 degrees? And you could just tack the same spot again?

Double nut option - I only have one nut, does anyone have the specs for that nut if I can source a second?

And... does all of this mean that a single nut with the “folded tab” lock washer is simply unreliable on its own?

Thanks again for all input. I really appreciate it.

Peter

Peter, If you wanted to do a low impact dab between the threads and nut, it would not be the end of the world. If there were room for a second nut, then that would be the area to tack together, the joint between the two nuts. I don't think you have that, because you have a single nut. On my trans, I (Dave) made sure the torque was correct on the 5th gear nut. I'm confident mine is good for the life I'll own my car. Again, silicon bronze, or similar. Pat

It seems to me that if you tack the two nuts together then you have just created one extra wide nut and now you have lost the advantage of a jam nut. I have to wonder just what percent of transmission have had the nut back off and at what mileage. I don’t see the chances of many of the roadsters being rebuilt today seeing high mileage again.

Thanks guys. It sure seemed like there was plenty of room for a second nut. And I like the idea of a jam nut. I always felt the same as Mike, that tacking them together just makes one big nut.

But, I guess if you “pre-jam” the nut, then the jam nut won’t “unjam”?

Tacking is not out of the question nor is double nut, I just need to know the spec of the nut.

Hoping someone sees this, knows the spec and I can somehow find one in the next two hours...

Tall order.

I seem to recall, I think, that JT had those nuts available?
Otherwise Ross probably has some used.

FWIW : This "improved" rear nut is what I ordered, installed, and is shown in the pic....

From Rallye's parts page:

http://www.datsunroadster.com/SUB_SECTI ... _small.htm

20 323-14 NUT, MAINSHAFT 5th double nut type, rear, improved, with shoulder
to help prevent trans. detonation NI

Thanks Mike.
I think Dave has a couple.