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Transmission Rebuild

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#21
Johnny D

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#22
Bench Racer

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you should post a picture of the modification. you know they say they are worth a thousand words. :)


Communication, hmmmm.

Using Mark's video for a picture the modification is as follows.

Let's identify the .0975 inch diameter syncro spring anchor hole is in the outside diameter of the counter bore of the clutch hub.
Let's identify the lower surface 90* perpendicular to the counter bore outside diameter as the bottom of the counter bore of the clutch hub. The distance from the outside diameter of the syncro spring anchor hole to the bottom of the counter bore is .0115 inch.

Visualize this being the .0975 inch dia. hole. > O
Visualize this being the bottom surface of the counter bore. > _
With hand file remove all steel from the sides of .0975 dia. O
hole to the bottom _ of the counter bore the full length
of the .0975 inch diameter hole from the outside of the tooth
to the counter bore of the clutch hub. With this relief filed
as described (EDM would be better) the syncro spring may kiss
flat to the hub counter bore bottom and there will be no
interference fit, no equal force from an opposite direction
for parts to stack up against and break the syncro spring.
Presumed the syncro spring hangs up on the side of the .0975
dia. hole to cause the interference stack up.

Will bring a modified clutch hub to the Runoffs.


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#23
SaulSpeedwell

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Mark, I thought a pm was a personal message.That aside when we have Miata 5 speed transmission Syncro springs and or syncro rings breaking there is logical reason for the breakage. Through Mark's investigation he found the cause to be brittle springs, he improved the springs and increase spring life 3 to 4 times.With the transmission apart and examining hubs, sliders, keys, Syncro springs and syncro rings I'm saying to myself, in order for something to be damaged or break there is a force and for every force there is areaction force that is equal and in the opposite direction. Before measuring parts I did a parts color transfer similar to what Mark did in his videos and yes the color transferred.In this case the cause of the reaction force is a parts (syncro ring, syncro spring,clutch hub) design/dimension/manufacturing interference stack up of .0102 inch to a clearance of .0035. Two different spring material cross sections measured were .048 and .054 and I used the.054 for the dimensional stack up. The hub anchor hole for the syncro spring in the clutch hub is per gauge pin .0975 inch diameter. The .0975 diameter spring anchor hole is up .0115 inches from the bottom of the clutch hub counter bore bottom surface. During forming of the 90* bend in the syncro spring a .006 inch bulge on each side seemed normal.I could go through the stack up numbers to make the communication more cumbersome but Let's skip that.Next with a hand file I shaped the bottom of the syncro spring anchor hole in the clutch hub so the side/bottom of the hole are as deep as the bottom of the clutch hub counter bore with square corners. Redid the color transfer and no colored transferred.Conclusion, with no reaction force, syncro spring and syncro ring life will be extended way out there.Another angle I'm working on is to find some syncro springs similar to those used in Jeep, Toyota, Muncie transmissions. These springs anchor on the first and third syncro keys, hence no reaction force.Of course my investigation is for use in an F production transmission.But then, one of the philosophies of Spec Miata is cost effectiveness of building and racing a car, correct.


The problem is the square root of Everest ..... :)

To David, About His Education by Howard Nemerov

The world is full of mostly invisible things,
And there is no way but putting the mind's eye,
Or its nose, in a book, to find them out,
Things like the square root of Everest
Or how many times Byron goes into Texas,
Or whether the law of the excluded middle
Applies west of the Rockies. For these
And the like reasons, you have to go to school
And study books and listen to what you are told,
And sometimes try to remember. Though I don't know
What you will do with the mean annual rainfall
On Plato's Republic, or the calorie content
Of the Diet of Worms, such things are said to be
Good for you, and you will have to learn them
In order to become one of the grown-ups
Who sees invisible things neither steadily nor whole,
But keeps gravely the grand confusion of the world
Under his hat, which is where it belongs,
And teaches small children to do this in their turn.
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#24
Bench Racer

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From one who is not within the 2%.

 

Ok, why are syncro rings marked by the corner of syncro spring when the spring is not broken/cracked/or disfigured?

 

The last guy from Ohio selling race car parts with an attitude was Jam Susko. When it was suggested his part had a dimension between 2 holes that didn't match an OEM part, he suggested I owned the only Mazda RX7 in the world with that dimension because none of his other customers complained. Yup, sure, ok Jim. 


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#25
Johnny D

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The problem is the square root of Everest ..... :)

To David, About His Education by Howard Nemerov

The world is full of mostly invisible things,
And there is no way but putting the mind's eye,
Or its nose, in a book, to find them out,
Things like the square root of Everest
Or how many times Byron goes into Texas,
Or whether the law of the excluded middle
Applies west of the Rockies. For these
And the like reasons, you have to go to school
And study books and listen to what you are told,
And sometimes try to remember. Though I don't know
What you will do with the mean annual rainfall
On Plato's Republic, or the calorie content
Of the Diet of Worms, such things are said to be
Good for you, and you will have to learn them
In order to become one of the grown-ups
Who sees invisible things neither steadily nor whole,
But keeps gravely the grand confusion of the world
Under his hat, which is where it belongs,
And teaches small children to do this in their turn.

 

I miss Andrew Charbonneau words and videos.

I know careful what you wish for. :)

J~


2011 NASA Western Endurance Racing Championship E3 Champ
We have a Winnah! - Won their 1st race... Congratulations! Beta-Tester - Assisted us with beta testing the website. Donor - Made PayPal donation Bona fide - A bonafide Spec Miata driver Novel Approach - When a paragraph simply won't do... Survive the 25, NASA Thunderhill - Survive the 25, NASA Thunderhill Instigator - Made a topic or post that inspired other Make it Rain - Made Paypal donation of $100+

#26
SaulSpeedwell

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From one who is not within the 2%.

 

Ok, why are syncro rings marked by the corner of syncro spring when the spring is not broken/cracked/or disfigured?

 

The last guy from Ohio selling race car parts with an attitude was Jam Susko. When it was suggested his part had a dimension between 2 holes that didn't match an OEM part, he suggested I owned the only Mazda RX7 in the world with that dimension because none of his other customers complained. Yup, sure, ok Jim. 

 

"Behind the smile, a hidden knife!"

― Ancient Chinese proverb describing passive-aggressive behavior

 

Which 2% are you talking about, 98% of the people on here are trying to help :)

 

If I assume you are trying to be helpful  .... the steel spring is harder than the brass synchro, but its fatigue life is far less.  No different than an ultra-hard chisel hitting a block of soft brass 20 or 100 times, and the brass happily takes it and shows the witness mark, but eventually the hard steel chisel fatigues and breaks and you have to regrind it.

 

That's why we try to "toughen" the synchro spring - so that the 90 degree bend that is work-hardened by virtue of the bend itself will take more strain.  Simply put, we want that tang to take as many "hits" as the brass synchro will take.

 

The brass synchro typically fails because it is a female brass cone being slammed over a male steel cone.  It is nothing more than a cone clutch, but we are asking a 3 inch $30 brass ring to make 7000 rpm of X100 lbs of engine/flywheel fury to "synchronize" with a rear drivetrain anchored by 7" wide Hoosier.  You can shift as fast as you want ... for about 40-80 minutes.  After that, the brass fatigues and cracks.


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#27
Johnny D

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This would be a whole new design but is there enough room to have a radius instead of a bend?

Kind of like ? shape and then continues left for a 90.

J~


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#28
SaulSpeedwell

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This would be a whole new design but is there enough room to have a radius instead of a bend?

Kind of like ? shape and then continues left for a 90.

J~

 

The thickness of the wire already creates interference with the synchro - but if you can get the rulemakers to allow any spring we can dream up, we would certainly not use a square wire with a 90 degree bend! We could even have a near-full-circle design that is slash cut to allow for the necessary deflection. 

 

The OEM Mazda design is really quite bad, but it works fine (for 150K miles?) unless you are trying to slamshift your way into 9th place during every shift of every lap of the R. Richard McRIchardson IV Memorial Regional.


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#29
Johnny D

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To be honest, I love what your doing giving the tranny durability, I'm all for it.

I question weather your already outside the rules, even though I think there may be no way to prove it without sending out the parts for hardness testing.

 

Are you bringing back the hardness to spec that Mazda had but has dropped off? then there no issue at all.

J~


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#30
SaulSpeedwell

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To be honest, I love what your doing giving the tranny durability, I'm all for it.

I question weather your already outside the rules, even though I think there may be no way to prove it without sending out the parts for hardness testing.

 

Are you bringing back the hardness to spec that Mazda had but has dropped off? then there no issue at all.

J~

 

I spent 8 years on the other side of this issue, responsible for the compliance of my own car in partnership with various suppliers, so I know what, why and how you are thinking.  I am up front with the videos, and SM isn't the only arena that these transmissions are relevant for.  It is entirely up to the owner what parts they elect for their car.  Many showroom stock titles were won with Sunbelt stickers on the fenders, long before SM was a thing. 

 

The springs are a bit hard to test for "hardness" - we would be using a Sharpe impact tester, which I simulate in some of the videos by using a chisel.  But the forks, for example, I feel like I have a good argument that we are doing nothing more than bringing the 2016 parts back to where the 1990-1999 parts were to begin with.  I have pages of hardness testing on stock forks of various vintage versus the new stuff.

 

Ultimately, it is the competitor's choice what goes in his/her car. 


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#31
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"Behind the smile, a hidden knife!"

― Ancient Chinese proverb describing passive-aggressive behavior

 

Which 2% are you talking about, 98% of the people on here are trying to help :)

 

If I assume you are trying to be helpful  ....

Already posted. I'm not within the 2%, therefore that'll put me in the 98%. Both you and I know what I meant by me not being in the 2%.

 

You would be correct in my trying to be helpful.  

 

The thickness of the wire already creates interference with the synchro -

 

The OEM Mazda design is really quite bad, but it works fine (for 150K miles?) unless you are trying to slamshift your way into 9th place during every shift of every lap of the R. Richard McRIchardson IV Memorial Regional.

Your point #1, thank you, we agree.

 

Your point #2, thank you we agree.

 

Again please keep in mind, within an earlier post, my stated goal is to improve the transmission for a F production/production car where massaging this part of the transmission is perfectly legal. If someone chooses to do so to their SM, so be it, it's their choice. It seems some of us agree there is a flaw within the syncro ring, syncro spring, clutch hub spring anchor hole shape and location or combination of these parts. Simple suggested again, if the bottom of the syncro spring anchor hole bottom is square and located to the bottom of the clutch hub counter bore there would always be nomally .023 inch (with the syncro spring corner burr) clearance and the syncro ring would not slam/crash into the syncro spring..................... The nominal space between the bottom of the syncro ring and the bottom of the clutch hub is .083 inch and that space basically will never change.......... Now, if the bend burr on the top and bottom of the syncro spring were fine ground/polished to elimination there would be another approx. .012 clearance for a total clearance of .035 inch with the syncro spring resting flat to the bottom of the clutch hub counter bore. Yes, if the syncro spring were not resting flat to the bottom of the clutch hub counter bore that's another condition, but IMHJ not nearly as bad a condition as the syncro spring resting half way up the OEM syncro spring anchor hole.  These numbers are from the 5th/reverse gear syncro rings, clutch hub and syncro springs.

 

A bit more transmission info:

 

Syncro Keys and Springs.

https://www.google.c...aVGoZS0M9dAY6M:

 

Muncie syncro rings, springs, hubs and sliders. Please note, the syncro spring may rest flat to the bottom of the clutch hub counter bore bottom. As will some of the other syncro springs from above address.


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#32
Bench Racer

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"Behind the smile, a hidden knife!"

― Ancient Chinese proverb describing passive-aggressive behavior

We agree on way more than we disagree on therefore eliminate your smiley knife.

 

How many SM folks already understand the syncro spring anchor hole and have modified to a square bottomed hole, or how many will now do it? Jim C. your not lurking, correct.


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#33
Johnny D

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I was thinking "a Lady in the Streets But a Freak in the Sheets"

But you can't beat a good Chinese proverb. :)

J~


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We have a Winnah! - Won their 1st race... Congratulations! Beta-Tester - Assisted us with beta testing the website. Donor - Made PayPal donation Bona fide - A bonafide Spec Miata driver Novel Approach - When a paragraph simply won't do... Survive the 25, NASA Thunderhill - Survive the 25, NASA Thunderhill Instigator - Made a topic or post that inspired other Make it Rain - Made Paypal donation of $100+

#34
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Johnny, posted the syncro ring/spring info relative reference to a couple of your comments.

 

I was thinking "a Lady in the Streets But a Freak in the Sheets"

But you can't beat a good Chinese proverb. :)

J~

Or a very similar proverb from a famous male baseball player, a cook in the kitchen, a lady in the parlor and a whore in the bedroom.


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#35
SaulSpeedwell

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As detailed elsewhere, the most expensive failures currently threatening the cost of Miata gearbox rebuilds are the gears and countershafts.  Those are failing less predictably, often more frequently, and always more catastrophically than the worries detailed in this thread.  If you want to pretend to worry about something on behalf of SM, worry about that one. 

 

For FP, just treat all those parts like you would any drivetrain component - drill, mill, chamfer, and polish away.  Use any treatments you think will help.


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#36
SaulSpeedwell

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Where is the AGPPS when I need it? :)


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#37
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It's info, if you find value, great, if you find no value in this info, then you have the same/similar knowledge from taking a transmission apart and inspecting the parts.

 

Often there are more than one cause which contribute to the broken synchro rings and broken synchro springs issue.

 

A follow up after examining/measuring all six synchro rings, springs and hubs. Synchro rings 1, 2, 3, 4 and 5 show signs of the synchro ring hammering the syncro spring at approx. the 90* bend during shifts. The reverse synchro ring showed no hammer marks. The six o' clock location of the bottom of the six synchro spring anchor holes within these three hubs varies from .006 inch below the hub floor surface to .025 inches above the hub floor surface. Final comment to help cure these broken parts is to forgo square siding the sides and bottom of the synchro spring anchor hole as previously mentioned because of the varying location of the spring anchor hole makes it a moot point.  Mill .040 inch off the bottom side of the synchro ring in the area where the synchro ring hammers the synchro spring. After milling clearance the synchro ring will not hammer the syncro spring during shifts.

 

For those that have taken transmissions totally apart, even if the synchro rings and or springs are not broken you have surly viewed the hammer marks in the synchro rings at the syncro spring 90* bend location.    


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#38
Jim Creighton

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"Behind the smile, a hidden knife!"

― Ancient Chinese proverb describing passive-aggressive behavior

How many SM folks already understand the syncro spring anchor hole and have modified to a square bottomed hole, or how many will now do it? Jim C. your not lurking, correct.

 

 

Jim C here!

 

My experience in 30 years racing with gear boxes was that I never broke one of my own gear boxes, but I repaired many customer gear boxes. Even gave a customer the one out of my car one weekend and he also broke that one. Speed shifting, power shifting, missed shifts all tear up the box. Treat the gearbox nice and it will be nice to you. And be sure that everything in the linkage is tight. A sloppy shifter will make a bucket of pieces box.

 

Watch some drivers in their on board videos and how they shift and you can tell who has very few to no gearbox failures. Smooth is faster.

 

 


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#39
SaulSpeedwell

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Plenty of gearboxes out there with the synchro ring relieved around the spring tang area.  The springs still fatigue and fail at the 90 degree bend because they cycle "circumferentially". 


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#40
Bench Racer

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Understand the circumference load. Interesting the hammering marks come when not shifting into a specific gear, but when shifting into the opposite gear of any pair.


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