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Old 09-28-2008, 05:31 PM   #1
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Default The Ultimate Automatic Transmission Setup

Ok, this is just talk for now. It might happen this coming summer, but I dunno. Mainly organizing my thoughts and looking for feedback and suggestions. No I'm not gonna go buy an auto 99 instead.

I've got a 99' with a 5 speed. I'd like to swap to a built up automatic this coming summer for several reasons. So far I can see there would be a few hurdles. Some minor, others not. However it could prove to be a fast, reliable, and consistent setup behind a turbocharged engine.

First, the hurdles. I'd have to find an automatic transmission. All 94+ miata transmissions seem to be the same, but Id like to verify this. I'll need the center console and shifter to accommodate the auto. They are electronically controlled by some transmission control module that sucks. They shift too soon and leave the driver with little control. I would use a standalone solution to take control of the auto. I would have to install an automatic transmission cooler up front to keep the thing cooled. Not hard to do, and I have a huge B&M transmission cooler in the garage. I think the driveshafts are the same, but need to verify that. Am I missing anything?

Now, I can figure out most of that, no problem. Controlling the auto with another computer is the main hurdle. From my research, nobody has ever done this on a miata. I can't even find a good wiring diagram of the auto. I'm gonna make one soon. Basically, you have a first to second solenoid, and second to third solenoid, third to fourth solenoid, a lockup solenoid, and then the various sensors like neutral, reverse, park, and speed.

Now, why would anybody want an automatic? Well, I like the consistency of an auto. Second, it would have some serious potential to be red light ripper with standalone control of the transmission. Can anyone say 4K stall, boost, and transbrake launches?

From my research, it seems something does exist that will control the transmission using MS2. It's called "megashift". It's put on the General Purpose Input/output board (GPIO board). This allows you to program all your shift points, lockup characteristics, and even setup different modes such as fully automatic, fully manual, paddle shift, etc.

But, where the hell do you buy this thing? I find all this info on it and no place to purchase it. What the hell? Maybe I'm blind, I dunno. Any info on this would be appreciated.

Here's a link to what I'm talking about. Click this, then click "MegaShift Trans code"
http://www.msgpio.com/manuals/index.htm
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Old 09-28-2008, 07:27 PM   #2
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Info's a bit sketchy about Auto trannied Miatas, not many tinkerers buy Auto's.

But from what i've gathered 94-97 used the Jatco L4N71B tranny, 99-04 used the Jatco A44DE.
The L4N71B used in my 94 has no electronic control for gear changing it's changing points are based on vacuum to the tranny valve.
The only electronic control is for locking the TC.

Not had mine Dyno'd but i'm running a 13psi MP62 so it should be between 220-240bhp the tranny is 100% stock and is holding up really well.

If you decide on the later tranny try this link for control.
http://www.powertraincontrolsolution...content-4.html

If you do a search on mnet there was talk of a group buy on these and one of the op's made enquires into buying and fitting one, but i've heard nothing more.



Cheers
Mark
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Old 09-28-2008, 11:45 PM   #3
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Quote:
Originally Posted by patsmx5 View Post
I think the driveshafts are the same, but need to verify that.
I believe the Driveshaft is different on the Auto. 90% sure.
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Old 09-29-2008, 07:21 AM   #4
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Nahhhhhhhhhh the Auto drive shaft fits on a manual conversion.

So it may be slightly different, but not enough that really matters.
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Old 09-29-2008, 01:24 PM   #5
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Here's what Mazda has to say about the wiring of the automatic transmission in the '00. I do not, unfortunately, have a detailed pinout or a truth table:






Technically, the propshafts are different between A/T and M/T. Here's the '99 parts diagram:



I think I remember reading somewhere that the two shafts are interchangeable, the difference being that one had a vibration damper and the other not. Or something like that...
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Old 09-29-2008, 01:55 PM   #6
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It's ok to say you want an auto for drag racing a Miata. Because if it's for anything else other than traffic, all those benefits can be had with driver improvement.
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Old 09-29-2008, 02:07 PM   #7
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Yeah, I drag race... That's the main reason I want an auto. I hate trying to worry about how I'm gonna launch and trying to read the tree at the same time. I can have a good light or a good 60', but not both. (used to bracket race my auto T-bird and I was in the final 4 every time. Miss that.) Plus I just think it would be "cool" to have a nice automatic setup. I'll adjust the bypass on the pumps so the auto can handle more power, tighten up the clutch packs, and let megaShift control the transmission from there. Should make for a FUN street car IMO. I like being able to launch from a red light. And yes i suck driving stick and have no wishes to become better...
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Old 09-29-2008, 04:16 PM   #8
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Quote:
Originally Posted by Joe Perez View Post
I think I remember reading somewhere that the two shafts are interchangeable, the difference being that one had a vibration damper and the other not. Or something like that...

I think that the vibration damper that you reference is on the flange of the diff. I had one on the 96 auto diff that I parted out.

Pat,

I have a 96 auto trans, plus everything to hook it up, including the shifter and linkage. I should have all of the connectors in the complete wiring harness that I pulled fron the car as well. Let me know if you are interested.
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Old 09-29-2008, 06:24 PM   #9
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Right you are. The diffs that went into the 5-speed cars got the damper, the diffs for the auto cars didn't. (weird...)

Ok, I have no idea what's different about the two shafts.
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Old 09-29-2008, 07:00 PM   #10
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Hmm, Looks like I need a A44DE for sure, so I'll have to pass Stein.

eunos1800- You seem to know a lot about automatics from my searching. Is the 99+ miata A44DE the same as the Tracker, Sorento, and all the other vehicles it's found in? Or are there differences? If I do the swap I'll probably find one from a miata just so I know it will work.
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Old 09-29-2008, 08:09 PM   #11
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What kind of power do you think it will take once you get into it a bit?
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Old 09-29-2008, 08:34 PM   #12
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Quote:
Originally Posted by JayMX5 View Post
What kind of power do you think it will take once you get into it a bit?
I'm not sure. I've never even SEEN an automatic transmission for a miata. From my readings, nobody has power related problems with them and I mean nobody. However, not many people push the auto like most here would push a 5 speed manual. Most I think I've seen is ~250whp on a stock auto. Research shows these transmissions were used in most mazda's and nissans back in the day, many bolted behind V6's.

If I had to guess, in stock form it will probably hold 300 wheel torque with adequate cooling. If I adjust the head pressures on the pumps (assuming it has two pumps like most autos), then I could probably run 400 wheel torque with no slippage. However, that doesn't meant the "internals" of the auto will take that much power. Odds are the sun shield is sintered steel and so is the planetary set. Ultimately it's these parts that will fail. Question is when. I doubt they'll fail on 350whp, but I'm no authority. Generally speaking, it's the rear suspension that tears up the trannys, not peak HP numbers. Make the car hook and the odds of breaking the sun shield on the 1-2 shift skyrockets.

I'm thinking up the pressures on the pumps, get a higher stall torque converter, and a huge transmission cooler to keep heat in check.
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Old 09-29-2008, 09:41 PM   #13
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I won't even begin to mess with the internal workings of a transmission, so I would be looking to find a company to build it for me. My only experience with an automatic is when I went with a fully built BTS transmission in my Lightning. I can't help but wonder if they, or another company outside of the Miata world would be willing to do a complete build on one of these things to make it almost indestructible. Having them build it was a bit pricey, but they stood behind their product 100%. They begged me to try and break it. That's what I would be looking for if I went with an auto.
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Old 09-29-2008, 10:26 PM   #14
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Quote:
Originally Posted by patsmx5 View Post
Hmm, Looks like I need a A44DE for sure, so I'll have to pass Stein.

eunos1800- You seem to know a lot about automatics from my searching. Is the 99+ miata A44DE the same as the Tracker, Sorento, and all the other vehicles it's found in? Or are there differences? If I do the swap I'll probably find one from a miata just so I know it will work.
Mines a Auto so i've tried to find out what i can, info's realllyyyyyyyyy sketchy though.
From what i've been told the A44DE part number covers the internals, the bell housings are different depending on the uses.
I've not see the other trannys though so can't say 100%.

Oddly enough there was very little info to be found over there (USA), the most of the good info i got was from Australia.
I was speaking with a company over there they recommended using the internals from a E4N71B tranny (used in 300zx's).
They recon dimension wise it's virtually identical to the L4N71B, but users harder planetary gears.
They were running (Drag racing) a 600bhp 300zx (no torque figures sorry) through a E4N71B for years without any failures.

I wouldn't worry about electronic control, companys like level 10 do valve kits that swap out the vacuum valve for a electronic one.
End of the day though you can get custom valves made that'll change gear at what ever rpm you specify, you can then just manual shift any other time.

Be good to see someone push these trannys.
They're really a bag of ***** stock, **** shifting, **** shifting points, no lock up in 1st or 2nd gear and a TC that's well below any decent stall level.

But with a bit more torque the trannys do really start to behave better.
Once your putting through more power there's actually enough torque to pull the badly spec'd gearing (it's something like 155mph at 7000rpm in top).



Cheers
Mark
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Old 09-29-2008, 10:59 PM   #15
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Well I've rebuilt a grand total on one automatic transmissions before, so I should be good to go.

eunos1800-where they swapping the transmissions on the 300zx or just swapping gear sets?

Honestly, I want the electronic control. For one, shift points will be infinitely adjustable (and adjustable with boost too). Two, I'll have a transbrake. Three, I'll be able to control lockup. Etc. And if there happens to be (not likely) a frequency controlled solenoid to control head pressure, I could even control shift firmness.

I know I could mod the valve body myself or have level 10 do it, but then it's not adjustable and you can't have a car with manners. In all honesty, I was hoping for this to be cheap. IE, buy the megashift stuff for say, 300, and wire it up myself.
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Old 09-30-2008, 09:16 AM   #16
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They were just on about swapping the gear sets.

I've had a look for the emails with them but they've gone, i'll do a few searchs and see if i can find the company as they were really helpful and seemed to know their *****.

If your looking to have electronic gear change by some thing like paddle shifts then i'd have thought any Auto tranny would do, as the position of the gear lever is not going to be critical?

From my admitted limited searchs the most tweaked Auto tranny seems to be the Supra.

Many Auto Supra drivers have gone for the AEM EMS which also controls the gearshifts.
When i last read through the forums though many were complaining about ***** gear changes though, so gear change tweaking may not be as easy to get right as a say car engine tuning.

Hopefully some guys with Supra experience can jump in and correct me if i'm wrong, but the stock Supra Auto trannys seem to hold together for multiple drag runs up about 600ft/lb.
Might need some tranny tunnel "adjustment" and a bell housing/engine interface plate making up.
But for that hassle you'd have a really strong tranny, that you can control electronically, that has ***** loads of parts and experience tweaking.


Cheers
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Old 10-15-2010, 04:04 AM   #17
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Originally Posted by patsmx5 View Post

I would have to install an automatic transmission cooler up front to keep the thing cooled. Not hard to do, and I have a huge B&M transmission cooler in the garage. I think the driveshafts are the same, but need to verify that. Am I missing anything?
I also need to install the Aceomatic Parts automatic transmission that I have. This was stock to me for almost 1year.
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Old 10-15-2010, 04:06 AM   #18
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Quote:
Originally Posted by clarkandrew45 View Post
I also need to install the Aceomatic Parts automatic transmission that I have. This was stock to me for almost 1year.
Dude, look at the ******* date on the thread before you post. Nobody has posted in this thread in 2 years, and your nonsense post was completely unneeded.
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