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I forgot to mention I have installed a bronze bushing since my original post, but haven't done much driving with it yet.
I don't have Second gear issues, and I have no problems finding Reverse. First to Second is very smooth. I get a split-second grind upshifting into Third, almost like I'm either not depressing the clutch far enough, or letting it up a little too soon. The Miata Five-speed, and my '07 Audi S4 Six-speed, don't need much clutch action once the car is moving. I plan to be very deliberate about my shifts at VIR this week. Most of my embarrassing problems were downshifts from Fifth to Fourth (Fifth to nowhere). |
Replace fluid with unicord blood you already own. If that doesn't fix, then syncro's are bad so toss tranny in trash. Then new(used) 6 speed with fix your issues.
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Originally Posted by IanIsInTheGarage
(Post 1584952)
Replace fluid with unicord blood you already own. If that doesn't fix, then syncro's are bad so toss tranny in trash.
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Originally Posted by Lokiel
(Post 1584927)
I've got the MR tall/angled shifter and aftermarket motor/diff mounts but would NEVER describe my MSM as anywhere near the best 6-speed I've ever used.
Looks like I need to add Amsoil MTG and the bronze bushing too. My MSM's gearbox was so crappy that I'd only find reverse gear about 1/3 of the time (REALLY embarassing in car parks as people look to see where the grinding gear noise is coming from. On the track it wasn't uncommon to accidentally find 2nd when looking for 4th, or 5th when you wanted 3rd, which really screws up your times and you spend the rest of the laps trying hard NOT to do it again instead of driving. On the road, especially around sweeping turns, I'd find "almost-reverse" instead of 5th when changing up from 4th - more gear grinding and your rear reversing lights come on to let everyone know you've fucked up. The MR tall/angled shifter fixed these issues but it's still far from what I'd call acceptable, it feels way too agricultural, as opposed to the slick 5-speeds I've owned or driven in the past (1982 Mitsubishi JA Starion, Mazda 3 and SP23, 1.6L NA MX-5). If you haven't got a MR tall/angled shifter yet, I thoroughly recommend it. I originally bought the short version because the tall-angled version looked odd to me when installed. Bill tried to talk me into the tall version but I got the short version and it was better than the OEM shifter. Later I upgraded to the tall/angled version and Bill was ABSOLUTELY correct, it made shifting even easier (especially reverse, almost no effort needed at all and you find reverse every time). I used black heatshink on the silver shaft and it virtually "disappears" in the car now. PS: Add a VooDoo knob, or some other round knob to the tall-angled shifter for the best combination. FYI: Many NCs, which use the Aisin 6-speed gearbox too, have 2nd-gear issues when cold. The AE86 too - one of my friend's sold his after 8 months, calling it a "Death Trap" because he had so many near-misses in morning traffic because he couldn't find 2nd gear when he needed and had to use 3rd instead. I drove him from Brisbane to Warrick, ~150km, to pick up the car because they were in high demand when initially released and the one in Warrick was the top-spec model he wanted. After the drive home he complained that the gearbox was shite which I attributed to just being different to his previous VW Golf gearbox but he clearly wasn't impressed with it.. Every time he took it back to Toyota, all they'd do was change the oil to a different brand to see if that worked - sometimes it did initially but the problems always returned a few weeks later. Apparently the Toyota dealers in Australia had an upper limit on warranty costs so swapping out the gearbox or replacing the car was not an option, which is why they simply tried changing the oil and hoped that it would fix the problem. Some Aisin 6-speeds are good, some are just shite and need to be avoided at all costs. If buying one, insist on driving the car in the morning when it's still cold. If it has 2nd-gear issues, walk away, it will always be problematic. If it drives well when cold, you've found a good 6-speed gearbox. Lot of it is the lottery of starting with a good trans. "The AZ6 Reverse Shuffle" is a thing on both of mine. (And nearly every other AZ6 i've ever driven) NC boxes are not the Aisin AZ6, they're the Mazda box found in the later RX8s. |
If you throw it in the trash use the trash can in my garage :rofl: id love a busted 6 speed to do...extraneous, nefarious things with
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Just spent a glorious day on VIR Grand. In five 30 minute sessions, I only missed a couple of shifts, still Fifth to Fourth. I did a personal best of 3:08.74. The motor mounts (and bronze bushing) did the trick.
I drove 216 miles to the track and I honestly did not ever notice the stiffer mounts while driving. If someone had done the replacement without my knowledge, I would not have known. That said, there were just a few times at idle (long wait at a traffic light) when I thought there was more vibration, but again, if I hadn't been looking for it, I would not have thought twice about it. I would have blamed the tune. The hybrid mount setup (OEM Comp Mount on the driver's side, aftermarket on the right) is stiff in the sense it secures the engine, but not so stiff to shake your eyes out. AWR is using a larger diameter bushing in their 70 duro mounts in order to reduce NVH. I'm a believer. |
Things aren't all unicorns, felatio, and IPAs, although they're way better with the new motor mounts. The Fifth to Fourth shift remains a problem on track. Lap to lap, it doesn't make any sense. Six out of seven times, the downshift to Fourth is easily and smoothly completed. But sometimes the transmission doesn't want to downshift from Fifth into any gear. Fourth should be easy to find in a panic--push in the clutch, let go of the shifter, then pull the shifter rearward.
What would cause this? |
If motor mounts helped but didn't remove the problem entirely, i would think poly urethane differential mounts would help too.
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The XT-M5-QS fluid that was mentioned make a noticeable improvement for the 6 speed shifting for me when I did it on my NC. It didn't have such a big effect on my NB, but it was still better.
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70 durometer poly engine mounts on my 140hp NB created a small "zizz" at idle which became less at running speeds. They improved the gearchange quite a bit. Stiffer rubber bushings might also have worked.
90 durometer ones on my 400hp turbo NB had the same effects except the vibrations were so loud and violent they nearly stopped the car be9ing my daily driver. |
Gents,
I'm the OP and this is relevant to me again... I emailed Bill at Miata Roadsters and passed him the story--basically cut and pasted from above--and he didn't believe one of his shifters would solve my problem. I have the magic Ford extra virgin, virgin unicorn oil and am contemplating trying the six speed again. What is the possibility--all funny/satirical/rude or dickish comments welcome--that the magic oil fixes my problem? She's HPDE only, but I'm averaging more than 25 track days per year. Thanks, |
You're still on the stock shifter? If so, I would spend the $$$ on the MR shifter. It's worth it.
Since my previous post in this thread I've upgraded to BBFW competition motor mounts (don't do this to a street car), and also caged the car. I'm pretty happy with the 6spd at this point, but I also still get the occasional 5/4 fucked up shift. Just the cost of a 6sp, IMHO. |
Originally Posted by Roda
(Post 1624543)
You're still on the stock shifter? If so, I would spend the $$$ on the MR shifter. It's worth it. but I also still get the occasional 5/4 fucked up shift. Just the cost of a 6sp, IMHO.
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Do these shifting problems happen towards the end of a session on a hot day or any time? It's pretty well known that the AZ6 doesn't like to get hot. The aluminum shift forks unique to the Miata AZ6 trans seem to not like high temps, and it doesn't take a bunch of power to get the trans hot since it's related to shaft speed (engine speed). Emilio has brought this up many times and even installs trans coolers to combat this.
I get gear lockouts once or twice a year. Usually towards the end of an afternoon session in July/August. And this is with a whopping 132whp. I rebuilt the box when 3rd started grinding and replaced all the synchros, clutch hubs, and shift forks. Measured all the clearances per the manual, and it made no difference. Basically I'll be motoring down the straight, shifting at 7000rpm, and out of nowhere I'll go from 4th to 5th and it will lockout. Feels like I've missed the gate. But I can stir the shifter around all I want and it won't engage any gear(4th/5th/6th) for a few seconds. Then after a few seconds of flailing around trying to engage something it will finally go in ruining my lap and at that point I just cool it down and park it. And I should note it doesn't grind when it finally engages a gear, so it's definitely the shifter mechanism and not the clutch hubs/synchros/gear cones. I've tried all the highly rated fluids (Ford, Amsoil, Redline) and found no difference between them, so I just stick with the Redline MT90 since it's readily available locally. I have Innovative engine mounts, poly diff mounts, and the MR shifter. I finally installed a trans temp sensor in the drainplug over the winter, so I'm hoping to find the temp threshold where the lockouts occur in the next month or so. |
Originally Posted by engineered2win
(Post 1624549)
Do these shifting problems happen towards the end of a session on a hot day or any time?
Originally Posted by engineered2win
(Post 1624549)
I've tried all the highly rated fluids (Ford, Amsoil, Redline) and found no difference between them, so I just stick with the Redline MT90 since it's readily available locally. I have Innovative engine mounts, poly diff mounts, and the MR shifter. I finally installed a trans temp sensor in the drainplug over the winter, so I'm hoping to find the temp threshold where the lockouts occur in the next month or so.
Thanks for the very informative post. |
I ran an MSM 6 speed for a short time. The ratios were ok for my uses but prefer the 5 speed ratios. My main gripe is the same as yours in that the shifting feel and accuracy was absolute garbage. Tried a bronze bushing and fluid before it started grinding in third gear and then i gave up entirely and went back to blowing up 5 speeds.
To be fair, once I used virtual dyno i realized I ramping in power a lot harder than i though which explains all the other broken gearboxes. I have since dialed it in softer on the bottom and they last much longer at higher WHP levels. One thing I have always been curious about is fabricating a transmission mount for the factory 5/6speeds. I have poly bush's everywhere else but I've wondered if installing some frame rail braces and fabbing up a transmission cross member with another rubber/poly bushing may help reduce the driveline flex. Im no engineer and haven't seen other do much about this. Had the idea after putting a similar setup in a LS swapped miata. |
Originally Posted by poormxdad
(Post 1624561)
You rebuilt the trans, use the juice, and installed the super shifter and still get the occasional lockout?
The only thing that seemed to help was insulating the exhaust. It was worse when I had a stock exhaust with cat and uninsulated exhaust tubes. It improved after I fabbed up a custom exhaust (deleting the cat) and wrapped the header primaries with DEI titanium and using DEI form-a-shield on the bottom half of the header and entire midpipe past the diff. Before it would happen pretty consistently toward the end of sessions regardless of ambient temps. Obviously a cooler would completely remedy the issue. |
Originally Posted by engineered2win
(Post 1624593)
Correct.
The only thing that seemed to help was insulating the exhaust. It was worse when I had a stock exhaust with cat and uninsulated exhaust tubes. It improved after I fabbed up a custom exhaust (deleting the cat) and wrapped the header primaries with DEI titanium and using DEI form-a-shield on the bottom half of the header and entire midpipe past the diff. Before it would happen pretty consistently toward the end of sessions regardless of ambient temps. Obviously a cooler would completely remedy the issue. Thanks much, |
Ford fluid and a GR shifter fixed all the mis-shift issues for me
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Originally Posted by Padlock
(Post 1624596)
Ford fluid and a GR shifter fixed all the mis-shift issues for me
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