Why do gears break on the stock transmissions?

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09-14-2009, 11:52 PM

#21

Savington

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My 6-speed use to grind almost every 1-2 and 2-3. Switched to MT-90 and they were gone within 3k miles. Just jumped to Amsoil/GM Synchromesh and they've stayed gone.

BTW - 3 trannies in 16k miles isn't ridiculous. I broke my 5 after 6k. thesnowboarder broke his at under 200whp after 1500 miles.

Last edited by Savington; 09-15-2009 at 12:06 AM.

09-15-2009, 12:38 AM

#22

magnamx-5

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Quote:

Originally Posted by bbundy

I have broken 6 of the 5 speeds. Driving style has very little to do with it. 300+ ft-lbs of torque and R-compound tires kills them in a short amount of time. I’ve broken 2nd twice, 3rd, twice and the gear that drives the secondary shaft and all gears but 4th twice. Gears stripped clean off.

I think I will try and find a cheap 6 speed until I can save the money for the Quafe. I still hate the gearing on the 6 speed. The problem I am having is I keep on getting 5 speeds for $75 or less and I haven’t found a 6 speed for less than $700.

Bob

you said 220 whp and then you come on this post and say 300 ftlbs lol stop contridicting yourself. Yes the 6 speed will hold up alot better. But the gearing isnt ideal obviusly. If you have the no how and tools etc the quafie is a better deal.

09-15-2009, 07:43 AM

#23

GrahamC

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I've been to the drag strip once with this car, so hard launches have very little to do with it. I drive my car hard, but I'm certainly not hashy with the gears. I drove this car for a year N/A and never had any problems. I've also been driving manual cars for over 7 years and never broke a box before.

It seems that the boxes plain can't handle the power. That, or maybe its Flatshift...

09-15-2009, 08:22 AM

#24

ArtieParty

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Quote:

Originally Posted by GrahamC

It seems that the boxes plain can't handle the power.

That must be it. That's why my 275hp/263tq car has 20k of turboing on it and Paul's 311hp car has probably like 25k on it and both haven't blown a trans yet. And we ain't driving grandma around town either.

09-15-2009, 09:07 AM

#25

hustler

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Quote:

Originally Posted by ArtieParty

Deduct 10-12% for using dynojet garbage.

09-15-2009, 09:20 AM

#26

sixshooter

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Quote:

Originally Posted by magnamx-5

you said 220 whp and then you come on this post and say 300 ftlbs lol stop contridicting yourself.

Hey, buddy, those were two different guys. GrahamC with 220 and bbundy with 300.

09-15-2009, 09:35 AM

#27

tyson87

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let me ask,
is there a difference in strength between the na and nb 5spd?

09-15-2009, 09:40 AM

#28

ArtieParty

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Quote:

Originally Posted by hustler

Deduct 10-12% for using dynojet garbage.

You're just upset cause your car sux. You should've invested in a IM with larger TB first.

09-15-2009, 09:52 AM

#29

hustler

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Quote:

Originally Posted by ArtieParty

You're just upset cause your car sux. You should've invested in a IM with larger TB first.

Why do you have to act like a ------ around me all the time? Friendship annulled.

09-15-2009, 12:25 PM

#30

bbundy

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Quote:

Originally Posted by magnamx-5

356hp and 321 ft-lbs on a dyno dynamics dyno at sea level with just 17 lbs of boost. I haven’t finished my last two track days with a transmission in tact.

I was making it through about 4 track days previously before upgrading the ECU and a few other things which upped the output a small amount.

Bob

09-15-2009, 01:14 PM

#31

magnamx-5

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ah my mistake i got cross posted bundy you are well past the know dangerzone for a stock five speed and need to consider doing something about it seriusly. No one has held much hope of more than 250 lb/ft through a stock tranny for any amount of time or abuse. For a long time. Either the FM gearset or the 6 speed would pay dividends for you.

09-15-2009, 01:20 PM

#32

wayne_curr

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Man you guys have me worried for my tranny and i bet i'm not even at 200whp yet.

What is the gearing like with a 6sp and a 3.63? I dont know how to do the math.

09-15-2009, 01:28 PM

#33

JayL

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Quote:

Originally Posted by wayne_curr

What is the gearing like with a 6sp and a 3.63? I dont know how to do the math.

If you make it down to Corksport this weekend you can take my car out for a drive. Should give you a better feel than looking at a chart.

09-15-2009, 01:30 PM

#34

wayne_curr

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Quote:

Originally Posted by JayL

If you make it down to Corksport this weekend you can take my car out for a drive. Should give you a better feel than looking at a chart.

As badly as I want to go to that, I cant make it :(

Edit:
Here it is, quoting savington from an m.net thread:

6-speed with 3.636 final
34.6 in 1st
57.3 in 2nd
79 in 3rd
103.4 in 4th
129.9 in 5th
154.1 in 6th (2952rpm @ 65mph, 3406rpm @ 75mph)

The idea of going from a 5sp with 4.3 to that is giving me a semi. I definitely know what i'm saving for this winter.

Last edited by wayne_curr; 09-15-2009 at 01:45 PM.

09-15-2009, 07:05 PM

#35

GrahamC

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6 speed box....... crossing the quartermile in 5th gear FTL.

Having said that, if it proves to be a durable solution then I'm all for it. Especially if it gives me a bit lower RPM when cruising on the motorway.

09-15-2009, 07:59 PM

#36

cueball1

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Here's the FM gear ratio calculator. Factors in tire size, 5 or 6 spd tranny, desired max rpms and has ratio's for the quaife gear sets too. Damn helpful tool.

Flyin' Miata : Technical info : Gearing calculator

I'd do a queef 5 speed gearset if it didn't cost as much as my entire car. I'm looking for a cheap 6 spd to go with the 3.63s I just got.

09-15-2009, 10:24 PM

#37

fahrvergnugen

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Quote:

Originally Posted by Savington

My 6-speed use to grind almost every 1-2 and 2-3. Switched to MT-90 and they were gone within 3k miles. Just jumped to Amsoil/GM Synchromesh and they've stayed gone.

If the grinds went away after 3K, why did you change again?

So what oils are everyone else using? I had planned to change that out soon after I got it running, but I don't know what oil is best for tranny longevity.

I am a firm believer in updating tranny oils, with VWs you can't help but crunch every aggressive shift into 2nd, but with MT90, I can downshift into 1st while rolling (no synchro on that gear, that might be on all manuals).

09-16-2009, 01:32 PM

#38

bbundy

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Quote:

Originally Posted by cueball1

Yea for a really high hp car a Quafe 5 wide ratio 5 speed with a 4.10 is what I want. The 6 speed really needs a 3.308 to not have silly 1st second and 3rd gears if there was a good easy solution for getting 3.308 in the diff I wouldn’t hesitate to go that route. The 3.636 is not quite there for the 6 speed still kind of silly 1st second and 3rd. A stock 5 speed with a 3.909 has really good gears but is pretty useless if it breaks every time you take it to the track.

Bob

09-16-2009, 02:35 PM

#39

ZX-Tex

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Quote:

Originally Posted by wayne_curr

The idea of going from a 5sp with 4.3 to that is giving me a semi. I definitely know what i'm saving for this winter.

That is what I did. 5-speed 4.30 to a 6-speed 3.63. Absolutely no regrets. 1st is still too short, but no sillier than it was with the 5-speed 4.30. Plus, I am not as concerned about destroying the transmission with 300 rwhp. 6th is really nice on the highway.

I have a spare 6-speed I may be selling off here in a couple of weeks if anyone is interested. I'm checking with the local crowd first to see if any of my Miata buddies want it. If not, I'll post it in the classifieds.

09-16-2009, 10:48 PM

#40

Dangasaur

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Weight of the car also has a significant impact on the stress the transmission receives. That said, I'm not sure that even removing a couple hundred pounds off a miata is going to improve the life of the 5 speed that much...

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