(Solved) 6 Speed 2nd Gear hard to hit - Miata Turbo Forum - Boost cars, acquire cats.

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Old 06-07-2015, 12:19 PM   #1
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Default (Solved) 6 Speed 2nd Gear hard to hit

I have flat shift setup on my '99 miata. It has a stock 18lb flywheel. With the SC pulling ~80HP from the crank, the revs drop pretty quick when flat **** kicks in. Datalogs show the engine will go from 8,500 RPM to 6,200 RPM in 0.34 seconds. So far the best I have managed is 0.40 seconds for the 1st to 2nd gear change using flatshift, most are .5 seconds though. If I try any faster I'll miss 2nd every time. All other gear changes are 0.20 seconds and consistent.

I rev to 8,500 in 1st, about 8,000 in all other gears. This results in the RPMs dropping to ~6,000 at each gear change. Flat shift is set to drop RPM to 6,000 with a fuel cut and timing goes to 5* BTDC (default).

I can pull back on the shifter very hard, and it just will not go into 2nd until the revs are almost exactly where they need to be for the next gear. The other gears seem to hit every time no matter what. If I shift at 8,000 instead of 8,500, I can't hit 2nd gear as the RPM difference is too much.

It has Royal purple oil in the trans right now. Also have AWR motor mounts, poly diff mounts, miataroadster shifter. I have the plastic 5 speed shift **** if that matters...

What is the problem? What can I change to make it better? I don't know if the 2nd gear syncro is worn out or what? Would a different oil help? Is there anything I can change to make the RPMs drop faster in tuning. I want this thing to shift!

Last edited by patsmx5; 06-08-2015 at 04:54 PM.
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Old 06-07-2015, 12:47 PM   #2
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Lighter flywheel?
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Old 06-07-2015, 12:51 PM   #3
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Yeah I know that would help, but I'd have to pull the trans to swap it. And the heavier one reduces the torque peak going into the trans, so that will help keep it alive. Heavier one also helps my idle a lot since I have a hotside SC setup, idle dip with the lighter flywheel was pretty rough...

Is there anything else? I was just looking at the flat shift settings, it will let me put a -90* of timing when the flat shift kicks in. Maybe that will help a touch if it's still firing a bit before it burns up any remaining fuel.

I'm curious about oils too.
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Old 06-07-2015, 01:11 PM   #4
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Is the Royal Puple gear oil GL-4 only? Try running Amsoil or Ford Motocraft. That is what most guys using 6 speeds use.
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Old 06-07-2015, 02:00 PM   #5
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I don't know what kind of RP Gear oil it was to be honest. I bought it a long time ago back in 2005 or 2006 for another car, never used it, and in 2013 I needed oil for the 6 speed and had 5 quarts of new RP Synthetic oil that was the right viscosity so I used it.

I'll look into those oils. Do you happen to run either of them by chance?
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Old 06-07-2015, 02:11 PM   #6
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I don't have the bottle but I just kinda remembered I DO Think it said GL5 actually. Is that the wrong stuff? I'm still reading about ford fluid, m.net reviews look promising.
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Old 06-07-2015, 02:35 PM   #7
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Did some reading looks like I probably have wrong oil in the 6 speed (GL5 not GL4). Going to buy some Amsoil MTG tomorrow and try that, I know a local Amsoil dealer so hoping they have it in stock. Will report back if it helps! Thank you Lars for the heads up on this, I would have otherwise never figured out I had the wrong oil...
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Old 06-07-2015, 02:44 PM   #8
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Stupid rear end (4.77 Kia might work) and start in 2nd?

There is always the option to avoid the problem by a complete rebuild elsewhere in the drive-chain.
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Old 06-07-2015, 02:46 PM   #9
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Haha nope, then all my other gears would be even shorter than they already are! I need a 3.636 gear badly....
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Old 06-08-2015, 12:44 AM   #10
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Yeah some ford motorcraft synthetic will probably be the ticket, or a lighter friction disk on the clutch.
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Old 06-08-2015, 12:46 AM   #11
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Jonathan, what do you run? I found some post on m.net saying both fluids are good, but I actually found 2 different post where people went from the ford to the Amsoil and reported it was better. Tempted to try the Amsoil, especially if my local shop has it.
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Old 06-08-2015, 12:47 AM   #12
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I like the motorcraft. I have redline MT90 in it now because it was given to me and I didnt have time to order more motorcraft because 1 night tranny swap.
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Old 06-08-2015, 03:07 AM   #13
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I have been using Amsoil for 5+ years in my 6 speed. Only because I have been able to get it cheaper then the Ford Motocraft fluid. I think it generally comes down to user preferences between the two.
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Old 06-08-2015, 02:53 PM   #14
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Well local Amsoil dealer didn't have the right stuff, so I bought the Motorcraft at the local ford dealer. About to change the trans oil now. Will report back if it helps any. I'm optimistic after reading all the reviews. I'll be thrilled if this makes the 1-2 gear change faster though!
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Old 06-08-2015, 04:37 PM   #15
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I use amsoil in my MSM six speed. I have a lighten flywheel (exedy) and aftermarket clutch (ACT Street Disc), and I have issues with second gear as well. I am using Amsoil Severe Gear, and Synchromesh (just because it's a combo I've used since, well forever lol).

I think it may have to be an issue with the clutch adjustment rod for me. As my engagement point is at the bottom (not very bottom, but close)
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Old 06-08-2015, 04:45 PM   #16
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Quote:
Originally Posted by ihiryu View Post
I use amsoil in my MSM six speed. I have a lighten flywheel (exedy) and aftermarket clutch (ACT Street Disc), and I have issues with second gear as well. I am using Amsoil Severe Gear, and Synchromesh (just because it's a combo I've used since, well forever lol).

I think it may have to be an issue with the clutch adjustment rod for me. As my engagement point is at the bottom (not very bottom, but close)
Yeah adjust the clutch for sure. I have mine set to engage very close to the top.

UPDATE: Got the Motorcraft fluid in. Night and day difference. It's like I poured syncros into the transmission.... All gears are easier to find/require less effort.

the 1-2 shift is much better. I won't say perfect, it's no hot knife in butter, but it's at least possible now. I can now drive 55mph, let the motor idle in nuetral, and it will click into 2nd. That would never happen before. Like I said, it's like I poured in a bottle of synros...

Pulling datalogs now... Will post shift times when I have them, but it's better, and it's a lot easier.
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Old 06-08-2015, 04:50 PM   #17
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New 1-2 shift was 0.25 seconds!!!! A couple were 0.29 but this is still a very significant difference!

Thanks for the suggestions gentlemen, very much appreciated.
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Old 06-08-2015, 05:30 PM   #18
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Quote:
Originally Posted by patsmx5 View Post
New 1-2 shift was 0.25 seconds!!!! A couple were 0.29 but this is still a very significant difference!

Thanks for the suggestions gentlemen, very much appreciated.
Glad it worked out for you. I will give the Ford fluid a try next time I fill a 6 speed so I can see how it compares to Amsoil.
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Old 06-08-2015, 09:14 PM   #19
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Quote:
Originally Posted by patsmx5 View Post
I rev to 8,500 in 1st
Any vids or a build thread?
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Old 06-08-2015, 09:15 PM   #20
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