My Six-speed Hates Me
 

Gentlemen,

Are there some secrets to making six-speed shifts?

This is a serious plea for help. I blew up my five-speed on track a month or so ago, and replaced it with an early NB six-speed I had stored in the garage for about four years. I've done three track days with the six-speed and I probably still miss a dozen shifts during a 30 minute session.

I'm running AmSoil MTG. Second to Third seems notchy on track, but not on the highway. Fifth to Fourth is embarrassing if the car is not moving in a perfectly straight line. I suppose I have some innate muscle memory going on when shifting, but there have been times downshifting to Fourth where I've ended up just putting the transmission in Neutral and pointing people by.

I also rebuilt the shifter with new bushings, so I don't believe anything is to blame but me.

Any suggestions would be greatly appreciated.

Magic Ford transmission fluid fixed my MSM.
XT-M5-QS
Worked far better than I expected.
Smells weird, not like normal gear oil at all

Miataroadster short shift kit transformed how my 6-speed shifts. Expensive but worth it.

Redline D6 ATF is supposedly an equivalent, which explains the smell (ATF is very mild), however I wouldn't suggest using the Redline ATF. I will say that BMWs use ATF in their manual transmissions though...

I have always run MT-90 in my Miata 6-speeds and they both shifted great. One of them I cooked the input bearing -- no idea if that's fluid related or just general track abuse.

--Ian

I found using a bronze shifter bushing and mt90 to be the magic sauce for me

Could the shifter be moving around from worn/insufficient engine or differential mounts? That could explain why the gate your after might not be where muscle memory puts it on the street versus the track.

Mine has Redline heavy shockproof gear oil, a factory shifter and a brass bushing as a data point. No shifting issues.

I can't get your link to open. Did you get stock height or extended?

I purchased two quarts of that Motorcraft oil years ago. I never put it in. They're in the garage. I ordered from the very local, tiny Ford dealership down the street. When I went to pick up my order, the parts guy asked me what it was for. When I said "Miata", I thought he was going to put them back under the counter.

I suppose the cheapest thing would be to try a bronze bushing before draining the nearly new MTG, unless the MTG us just the wrong oil for the six-speed.

I can feel, and see, the shifter move around a bit when accelerating or decelerating, but the five-speeds I've had were the same way. It happens in my stock '90 shitbox, too.

Thanks,

Engine mounts solved mine
 

Engine mounts with a 70 durometer bush solved 90% of my miss-shifting.

Another vote for engine and/or differential mounts. I couldn't hit 2nd to 3rd on track to save my life with stock mounts. Turns out they were completely destroyed when I pulled them out. AWR engine mounts solved all my driveline slop/mis-shifting issues.

When I bought my Ford fluid it had been on the shelf at the Ford dealer for 4 years.
They had never sold any.
I had them check to see what it "fit" in the Ford line up.
They told me the only application they could find for it was the mid 2000s GT40...
I believe it had a "Ricardo" gear box.
It didn't smell like ATF either.
I didn't believe it would really help but it made huge improvements.
All the other suggestions are all spot on.
But, especially if you already have the fluid, give it a try first and see if it helps you too.

I've run the following in all my 6 speeds and haven't had an issue missing shifts. Bear in mind i've clocked maybe 3000 miles ever in 5 speed miatas, so this may just be a muscle memory thing for me as well.

Amsoil MTG
MiataRoadster Tall/Angled shifter
Carbing High Grip knob
Delrin or bronze bushing
Aftermarket motor/diff mounts

Easily the best shifting transmissions i've ever experienced, and my DD is an S2000.

Extended angled version, which places it very close to the wheel for easy shifting. I also installed a stock height version in my '93 street car (converted to 6-speed), mostly for looks. I, by far, preferred shifting with the one in my track-mostly MSM.

The website seems to be a little bit flaky at the moment. E-mail Bill Wilner directly (Bill@MiataRoadster.com) with any questions. Great guy to deal with.

Thanks!

I could just say '+1', but...
I switched from 5sp to 6sp in my track NA about a year ago. It does take some getting used to, and if you don't street drive it, it will take a little longer to build the muscle memory. My setup:

Mazda competition motor mounts
Amsoil MTG
Miataroadster shifter -tall/angled.
Bronze bushing

Probably the biggest difference for me was the Miataroadster shifter (and it was the last change)... expensive but worth it.

Here's a pic of the driver's side motor mount. Replaced with a Mazda Competition mount. I haven't pulled the other side yet. Waiting on an AWR 70 durometer to arrive.


https://cimg3.ibsrv.net/gimg/www.mia...ad49a92001.jpg

That certainly didn't help your shifting.

Please report back how you like the hybrid mount setup. I have mazda comp mounts on mine and was considering trying a poly mount on one side.

Took the car out yesterday with the hybrid mount setup. At speed, I really don't notice any new harshness, but I will admit at idle there might be some added vibration. I need to spend some more time driving her. My next track event is coming up at VIR. I'll know then if the mounts help my shifting.

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.