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High RPM shifting dynamics


duragg

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I was going to offer you second gear from my trashed 5 speed but whoever broke it wore the dog gear pointss down to a lean-to shape from the original peaked, before the shift forks broke and the adapter plate bearing balls came out.

 

Don't forget to check the leading edge of the inner splines/teeth on the coupling sleeve.  If the dog teeth are beat, they might have some damage also.

Edited by NewZed
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If the cone is good I am going to sharpen them all and try that.

 

That fork damage / wear is a great reason drivers need to keep their paws off the lever after shifting.

It is not unlikely that in the past the driver of the doner ZX this box came from was a hand-rester.  Holding his hand on 2nd while accelerating and pushing the rod forward, causing wear to the fork sides.

 

I am interested to see what the latest version of the fork looks like when it gets here.  That may be why they are using those plastic tabs, to keep some space and prevent that wear.  Who knows.  Nissan does have a Service Bulletin about the forks but I cannot find it or see it.  It is not in the TSBs I can get from Identifix either.

 

Excited to make these changes once the parts come in and see how it all goes.

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Agreed NewZed.

The Coupling Speeve is common to 1/2 and 3/4.  I may be able to sharpen the points and switch 1/2 for 3/4, suspecting 1/2 takes the most abuse.

 

This pic has a good close up of the dog teeth.

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Something else suggested to check out since you got the trans apart again is how the brass rings sit against the gears.

You can check this by putting some oil on the inside/outside of the brass synchro and on the polished angled surface of the gear where the synchro sits.

Hold the grear in your plams and press the brass synchro against the gear with your fingers with equal pressure and make sure it does not rock at all. Check this all around the entire gear, and even put the synchro in various positions.

If that checks out good, the next test is to spin the brass synchro on the gear using hand pressure; it shouldn slide (spin) around the gear with the same amount of drag.  If it does not or binds in spots, it might be better to replace that synchro. 

From your picture, it looks like you have ample gap, so the brass syncho does not look stretched out.

 

Good luck

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The brass synchro you see on the left is toast.  In that picture it is in the relaxed (retracted) position.

If you watch the video I engage 2nd and you can see the ring bottom out, no clearance.


All new synchros are inbound soon I hope.  Haven't got tracking number yet.

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Dove into teardown today and took a bunch more pics.

I ask the Managements permission to post some larger pictures so that future generations can gleen data from them.

 

WARNING:  I rebuilt this tranny last and sometimes it is tricky to know which exact way parts go together and the manual is unclear.

 

Anyway, the point of this thread is to discuss and learn more about slick shifting old school Datsun Trannys.  This is for the DIY types.

 

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Interesting link: http://www.gforcetransmissions.com/face-tooth.asp

Another good read: http://www.brokevw.com/gear_selection.html

 

More thoughts about transmissions while I am waiting for my parts to ship.. (GRrrrr).

* Resting your hand on the shift lever will wear out the shift for faster and send wear metals into the oil and synchros.

* ANY grinding in any gear is bad and sends wear metals into the oil and synchros.

* Leaving a car in gear while parked for extended periods of time results in the synchro spring staying compressed which won't make it work any better in the long run.

* Thicker oils have significantly greater drag among the gears and make the synchro work harder.

Edited by duragg
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Interesting link: http://www.gforcetransmissions.com/face-tooth.asp

 

Another good read: http://www.brokevw.com/gear_selection.html

 

More thoughts about transmissions while I am waiting for my parts to ship.. (GRrrrr).

* Resting your hand on the shift lever will wear out the shift for faster and send wear metals into the oil and synchros.

* ANY grinding in any gear is bad and sends wear metals into the oil and synchros.

* Leaving a car in gear while parked for extended periods of time results in the synchro spring staying compressed which won't make it work any better in the long run.

* Thicker oils have significantly greater drag among the gears and make the synchro work harder.

Those links provide some good basic advice on the mechanics of the most common manual transmissions.

Think you said your car makes less than 1,000 HP, and you shift point is under 8,000 RPM, so you should have no problems with the 1-2 shift with a properly rebuilt stock unit.  Again make sure you check out the fit of the new brass synchros on your gears, and confirm they do not rock or bind when spun by hand on the gear.  Also the slider (outer shift hub) should be smooth over the inner hub without the dogs installed.

 

There are many tricks the old school drag racers used to make manual trans shifting easier; try looking at threads discussing Muncie, Borg Warner T-10, or Hemi 4spd trans.  Some of easier tricks involve the dogs, dog springs, dressing the hubs and slides.  More agressive mods involve removing every other tooth of the gear, brass synchro, and slide; but would not recommend that for a street driven car.

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Finished tear down tonight. Pics to follow.

Unfortunately 2nd gear sync cone appears goldish in color which I assume is the end of the hard chrome plating and the beginning of thw sub-plating and the end of the line for this gear. It will quickly consume any synchro ring.

 

Nissan is Back Ordered so this whole rebuild just took a month delay.

Unless I can scour the earth for one on a shelf somewhere.

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Pic of 2nd gear cone. Should be clean solid chrome, but it is worn down to some underplating material (copper?) Any new brass ring will be rapidly worn away again. Trying to replace this part (32250-e9200 or e9260)

 

 

You can also see wear marks on the face of the 2nd synchro ring on let and good 1st on right

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Could it be transferred brass?  The dog teeth look pretty rounded anyway, don't they.

 

The brokevw link had some good focus on the "sync keys", or "inserts" as Nissan calls them, and the springs underneath. I don't think that people pay much attention to them since they're small and it's not obvious what they do.  There's a Hybridz post out there by HizandHerz about doing some work on the "baulk springs".  I assume that he means the insert springs.  You might have seen it already since he also mentioned lapping the synchro surfaces.

 

http://forums.hybridz.org/index.php/topic/58315-280zx-rough-shiftinghelp/page__p__537658__hl__synchro__fromsearch__1?do=findComment&comment=537658

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Could it be transferred brass? The dog teeth look pretty rounded anyway, don't they.

 

I was hoping for transferred material but you can feel the worn spots where the chrome is gone. I hit it with 3M pad to be sure and showed it to BigMike (plating and superfinisher) confirmed dead. Yes to the teeth also. Lots of good reasons to RedTag that gear.

 

On to the springs. I am tempted to play with those. I may just order new. Or put a small spacer to increase the push. These keys keep the slider stable and push the brass ring onto the cone when shifting. So. Heavier springs might marginally increase shifting force and might cause speed matching a little sooner. I will experiment with this and report back.

 

As for lapping, I did lap the new brass rings to these cones in 2009 when I last worked on this box. Lapping compound is very aggressive and doesn't make the chrome last any longer. Maybe I broke into the thin aging chrome then. Once the chrome is gone, the underlying material will eat the brass virtually instantly. Still considering this for round 2 rebuild now.

Edited by duragg
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Lots happened today.
Found a 1980 5 speed with perfect gears. Picking the best parts from both to make one box. The C/G bearing in this new box was literally gone. No trace except a few balls and some race.

Mike at SuperFinishers examined the synchro cone discussed above and it is NOT chrome but hardened and ground to that shape. We were able to remove the transferred brass and make a better surface. I was wrong on the material. The teeth are still nubby so I will use my newer gear.

I am having fun again. I just knew there were rabbits in that hat somwhere.post-1894-0-48165200-1360036235_thumb.jpg

 

Editorial commentary: 

Funny thing about getting older.  I am a fairly impatient person.  Type A: Business Owner.  But with a lifestyle addiction.  We work hard, but nothing crazy.

So here I am wondering where I will find some NLA Z parts so I can make the race next weekend and the only option seems like having Nissan overnight one from Japan.  Nah.. I will just chill out till Monday.  I had some feeling that today, I would find what I needed.  It was no accident, I worked Craigslist and pulled that rabbit when I needed him to be there.

I probably need to just "chill" a little more often.  The rabbit is in that hat already.

Edited by duragg
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Being this a documentary about improving shift quality I am bypassing all the other Overhaul type stuff going on.

 

I have 2 trannies now.  One I pulled from a 1983 ZX and this new one is supposedly from a 1979 ZX but it is clearly a much later tranny as it has identical ratios to the 1983 model, but has the shorter ears, one leg and Passenger side fill port.

 

The 1/2 shift rod and fork on the 1983 models is totally different.  1983 model has the fork actuator receiver thing cast into the rod.  on  the earlier models it is a seperate piece that is pinned on.  Pics below.  Also the 1983 1/2 shift fork is a much larger, heaver piece and has 2 holes like the 5/R fork.   Is also has the pin in a different place.

So... 1983 type 1/2 shift rod and forks are totally incompatible with earlier models.  My 1983 1/2 fork was wasted and the part is No Longer Available.   They sent me a new one for the earlier tranny so I will be swapping some of those parts out to make one box work.

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Next I have collected all my sliders and need to pick the best 2.

 

1A  post-1894-0-63031100-1360127363_thumb.jpg

1B  post-1894-0-50498800-1360127364_thumb.jpg

 

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2A  post-1894-0-26507200-1360127365_thumb.jpg

2B  post-1894-0-03460300-1360127366_thumb.jpg

 

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3A  post-1894-0-81047100-1360127366_thumb.jpg

3B  post-1894-0-60745300-1360127367_thumb.jpg

 

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4A  post-1894-0-39992700-1360127368_thumb.jpg

4B  post-1894-0-18418100-1360127369_thumb.jpg

 

Edited by duragg
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