High RPM shifting dynamics

[duragg]

I am sorry for not taking pictures last night, but we were on a full court press to get the work done.

 

I split the tranny case and pulled the input and C/S bearing and gear which gave me access to the 3/4 gear cluster.

Swapped in my new keys, and new engage ring then measured the gap between the brass teeth and engage teeth it was still too far, allowing the keys to give up tension too early releasing the engage ring to grind onto the gear.

 

I machined off about .015" from the slot on the brass rings and this allowed the correct timing of the engage ring hitting the brass teeth just as the keys are just before their maximium tension so the blocking  remains until the speed is synced and the shift proceeds properly.

[Leon]

By new keys do you mean you shimmed them or just bought new ones? Any difference in shift effort?

[duragg]

I bought new keys from Nissan ($1.70 each).  They are now NLA, sorry.  Those were the last 4...

I took pictures of the new and old side / side and there was very little difference.

I tested the new and old keys in my little fixture on the scale and could tell no difference in the keys.

I think with the shimming under the keys you have plenty of control over the breakaway force. 

 

 

Of the various factors I have run into through this process:

Major Factors:

1) Brass Synchro in spec (so the have ability to provide sync braking effect).

2) Dog Teeth engage distance (so the force is properly applied during the sync braking).

3) Good condition shift forks to make sure engage slider moves as far as it needs. (so the slider is in position and cannot pop out)

 

Minor factors

1) slightly worn brass rings (will still work fine as long as they aren't bottomed out on the gear face)

2) condition of the engage teeth (sharp & new vs old and slightly rounded not a huge factor).

3) breaking the polished glaze of the gear cone (Allows better braking action)

4) type of oil (A great condition tranny would work with any appropriate lubrication).

 

As Jacks website noted, I think I could take an old and crunchy tranny, rebuild with used (but within limits) parts and do some of the tweaks mentioned above and have a perfectly good transmission again.

[duragg]

By new keys do you mean you shimmed them or just bought new ones? Any difference in shift effort?

I didn't touch the keys. I shimmed .060" under each key spring, but the keys are stock.

I think there has to be a slight increase in shift effort as evidenced by the higher key breakaway force due to the stiffer springs under the keys.  But this is negligible and I cannot detect it at all by stirring the lever.

 

My 1&2 gear have old keys, 3&4 are new. and no difference can be detected at the shift lever.

Edited March 20, 2013 by duragg

[Leon]

Excellent feedback, thanks!

[NewZed]

I machined off about .015" from the slot on the brass rings and this allowed the correct timing of the engage ring hitting the brass teeth just as the keys are just before their maximium tension so the blocking  remains until the speed is synced and the shift proceeds properly.

 Which slot?  The three that the keys ride in or  some other?  Trying to make sure I understand.

 

That was some solid work to figure things out and get it done.  And that guy Jack really dug deep on the mechanics of the synchros.  I've never really understood well how the various pieces worked together until this thread.

[duragg]

I ran the car hard tonight with race gas and I slammed 3rd gear "Like a boss" and  it slipped in perfectly / no crunch.  I win. 

I am eternally gratefull to "jacks" and I will send them an email so they know how much we appreciate their sharing information..

 

Slot:

There are 3 slots in the brass ring synhro and those are what I shaved from .0163" to about .0148" based on some measuring.

You can see it by preloading the gear and pushing the engage ring and watchin how much the synchro keys recede on the backside.

 

I swear its really hard to explain, but relatively easy to visualize once you have a test setup  and spend 3 months farking with it 3 hours and 3 beers a day.

[inline6]

Just read the whole thread here...  Thanks for putting all the time and effort into it and sharing as you went.  Absolutely awesome... you appear to be a crazy as I am when it comes to finding solutions to things that bug us enough.

 

I rebuilt my late style ZX box a few years ago. It was the first tranny I ever rebuilt.  I took on this endeavor because the first to second shift had soured... on high rev shifts from first to second (~6k in first), it was delaying too long, and if I forced it, it would grind.  I also figured the odds good it had over 180k miles on it.

 

I replaced all bearings (including needle bearings) all synchros and a some misc. parts (like the "bushing" the needle bearings ride on) - all with factory parts.  I certainly replaced more than necessary, no doubt as I had no idea what I was doing.  I used the FSM (factory service manual) every step of the way.  All the clearances worked out to be within their required ranges - I never even came across any info that anything might have to be lapped.  

 

I noted that the "teeth" on second gear - the ones that the shift sleeve engages, were "worn" like those on your second gear.  They didn't look horrible, but not like the other gears either.  I debated at the time whether to buy a new 2nd gear, or to file the existing teeth because I had no idea how "bad" mine was.  I ended up not being comfortable with the price of the new gear, nor the unknown damage I might cause with filing.  I hoped for the best that the new synchro would eliminate my main problem.  

 

I put the rebuilt box in the car, and the 1st to 2nd shift was much improved.  There was still a very slight hesitation, but it wasn't annoying at all and only there with full 6k+ shifts - with no grinding.  

 

(Some autocrossing - some track days - no issues)... Then fast forward a few years...

 

Recently, I got my new motor running.  This one is revving past 7k, and the problem is back... BIG time.  Those extra RPMs are a real problem.  My feeling is that a new second gear will solve the problem - as those teeth (what are those called?) looked to be the most worn part of the tranny last time around, other than the reverse idler gear, of course.      So, when I started your thread, I was pretty excited to see where it was going to land.  But, now having read it through, it seems like you started with the problem I have, and transitioned to a 3rd gear crunching problem (which congrats! you solved) by the end.  But I don't quite recall exactly how you fixed the original problem.  

 

So, is the first to second delay/crunch problem completely gone - even with your "old" second gear?  If so, what do you attribute that fix to?  My assessment from what I just read is:  a factory synchro instead of an aftermarket one?  And scuffing the brass off of the shiny surface the synchro mates to on the second gear?  Anything else? 

 

I was about to place an order for a new second gear tonight from nissanpartszone, when I went searching in this forum to see what there was...  (and I see now it may be on BO?   ).  And if it is on BO, then I won't be able to solve my issue with that solution, if that would solve it, that is.

 

Also, I was looking at the reverse idler tonight on a spare tranny I've got...  It looks reversible.  Anyone know if it is for sure?  Sure would be nice to swap that mangled mess on one side around to the other and put a fresh side into action.  

 

G

[AZGhost623]

I sucked up a lot a parts from nissanpartszone and driveline.com because I plan on doing the same thing with this 82 5speed I scored. Parts were not cheap, about another 400$ worth or so to go through and replace everything (which may not be needed), but while its open just do it anyways is my thought. Who knows what this 82 5speed has been through. Oh, and apparently Duragg sucked up all of the 5th gear parts, as its NLA now.

[NewZed]

  But I don't quite recall exactly how you fixed the original problem.  

 

So, is the first to second delay/crunch problem completely gone - even with your "old" second gear?  If so, what do you attribute that fix to?  My assessment from what I just read is:  a factory synchro instead of an aftermarket one?  And scuffing the brass off of the shiny surface the synchro mates to on the second gear?  Anything else? 

Re-read posts #117 and 133.  They hold the key.

[duragg]

NewZed:  I love the double on-tonn-derr of your post.  

AZGhost is my next victim, we bought him all the new parts and going to use all the previously gained knowledge to make him a new tranny with perfect performance from day one (we hope).

 

I've beat on the car a bunch now and all the squawks have been resolved.

1,2,3,4 and 5 all shift perfectly well with no grinding.

3&4 shifts a little faster than 1&2.  I tend to attribute this to some cleanup I did of the gear cone prior to reassembly.

I broke the gloss of the cone surface, not unlike turning rotors or resurfacing a flywheel.

 

Of course, i am having radiator issues now with harder track use and summer coming, but that is another story altogether.

Tj

[NewZed]

No word play gold star for me, I can't take credit.  It must have been subliminable.  I wasn't thinking it when I wrote it.

 

On that point though, could you shave the keys down on the sides to get the same effect as opening the slot?  Is there neough meat on the key?  And what about downshifting?  I assume the other side of the slot comes in to play.

 

It'll be great news for all rebuilders if this procedure is simple enough for the average mechanic to do.  I've read many threads around the internet about people rebuilding their Z transmission only to still have grinding problems afterward.  Thanks for documenting.

[duragg]

No word play gold star for me, I can't take credit.  It must have been subliminable.  I wasn't thinking it when I wrote it.

 

On that point though, could you shave the keys down on the sides to get the same effect as opening the slot?  Is there neough meat on the key?  And what about downshifting?  I assume the other side of the slot comes in to play.

 

It'll be great news for all rebuilders if this procedure is simple enough for the average mechanic to do.  I've read many threads around the internet about people rebuilding their Z transmission only to still have grinding problems afterward.  Thanks for documenting.

We are adjusting slot depth so the teeth are closer to each other (forward and backward, if you will)

The slot width would change how the relative alignment of the teeth is (Left/Right if you will) which was perfect on all the ones I looked at.

 

Making the slot deeper  brings the teeth closer to each other so they can touch prior to the keys being pushed out of their engage ring groove.

With this set, the impact will be corrrect for both upshift and downshift and I have hammered all gears up to 7300rpm power falloff and shifted great.

 

You bring up a point of making the keys shorter, and I think I considered that, but there may have been some issue with that.  For one, brass is easier to work than the hardened keys.

 

At the April race I will know more with the higher heat and stress of combat.

[duragg]

We should probably be clear on one thing... I screw-up half of everything I touch.

 

Everything I did could have been totally 100% raw luck due to some other screw-up which un-did the primary screwup.

I hope that is not the case,  based on research and studying just about everything I could find online.

I tried to test / apply / analyze along the way as best I could, but there are clear gaps in the scientific process.

It seems to me that tranny people as a whole are generally relutcant to give up their "secret sauce".

 

This thread is OPEN to any and all who want to add, subtract, multiply or divide the efforts herein presented.

[Xnke]

Just started a month of transmission work, and will be applying the information in this post. It's looking like I will have a bit of time before my jigging material arrives for a customer's transmission, so I'll have another go at rebuilding the "new" 5 speed in the floor.

 

If everything checks out good, then I'll not worry about rebuilding it and just bolt it up, but I'll be adding synchronizer checks into the rebuild requirements.

 

How did you re-torque the mainshaft and countershaft nuts? I've used a big wrench and a carefully selected weight, but surely there's a better way.

[duragg]

Years ago I took a giant socket, cut it and welded a pipe in the middle.

This made me a DEEEEEEP Socket to torque the Main Shaft nut.

I either gave that away or "klog" took it which is another story.

 

I need to do make another super-socket like that. There is a picture of its impressive length and girth somewhere here on Hybridz.

In the meantime I used a big wrench borrowed from a friend (1.5"?)

[Xnke]

I used a 1.5" wrench to remove the one on the 4-speed I broke down last night; but I was thinking about the deep socket idea. Probably will make one today.

[beermanpete]

I used a 36mm crow foot wrench. You can use it with a torque wrench but need to calculate the affec it has on the reading due to the length of the crow foot wrench.

[HowlerMonkey]

I think they make wrenches for inner tie rods on steering racks that might fit the bill......still might come up short, though.

[Xnke]

It turned out simple enough to cut a deep well 1.5" socket down, and weld a piece of pipe between the two halves. Might come in handy some other time, might not.