jnshk

I'm in the process of a retrofit of sorts (NB cluster into NA dash) and I've got nearly everything sorted out except for which NB vehicle speed sensor I need. Since my 1997 NA has a 4.1 rear end, then I assume that I need to get the speed sensor for an NB with a 4.1 rear end, but that's where the confusion starts.

After a lot of searching and reading, I've compiled a list of part numbers and characteristics, and almost every thread that I've read on various Miata forums indicates that the VSS gears equate as follows:

M527-17-400A - 23-tooth, Green >> 4.3
M526-17-400A - 22-tooth, Red/Burgundy >> 4.1
M528-17-400A - 21-tooth, Yellow >> 3.909
M534-17-400 - - 20-tooth, White >> ??? Never seems to get mentioned?
M533-17-400A - 19-tooth, Blue >> 3.636 (Australia market only)

According to Flyin' Miata (and other sources), all NB 5MT's came with a 4.3 rear end, early NB 6MT's had 3.909 and late NB 6MT's had the 4.1:
This doesn't seem to jibe with the Miata part numbers by application though. From what I can tell based on Mazda's info, it would be more along the lines of:

99-05 5-speed (non-sport) - 4.3 (green)
01-05 5-speed (w/ sport) - 4.1 (red)
99-00 6-speed - 3.909 (yellow)
01-03 6-speed - ??? (white)
04-05 6-speed - 3.909 (yellow)

I'm guessing that the 01-03 6MT white 20-tooth sensor is also intended for a 3.909, but possibly with a larger tire diameter? Did the tire size change for those year models? Can anyone clarify this?

I'm more inclined to go with the data based on Mazda's part numbers than Flyin' Miata's chart, which would mean I need the sensor from an 01-05 5MT Sport (M526-17-400A - 22-tooth, Red), but I'd really like some of you experts to weigh in and confirm before I spend any money.

Ben

iTrader: (33)

That would be an improper inclination. You would want the sensor from an NB automatic, as the autos had the 4.10:1 final drive. Another option would be from an MSM, but I'd wager that it's a lot easier to find a used sensor from an automatic than from an MSM. If you get a sensor from any NB 5-speed, you're gunna have a bad day.

Here's the thing though. You have an MS3-Pro? Run whatever speed sensor you have as the VSS input, then command the dash through the speedometer output. It allows you to scale for stuff like this.

aidandj

iTrader: (5)

Ben is this an MS3-Pro specific feature, or an ms3 feature.

jnshk

So then none of the NBs with manual transmissions had a 4.10:1 rear end? What's all the malarky about on Flyin' Miata's tech page and the countless (though admittedly, often ill-informed) posts on Miata.net about NB cars with a 4.3 having the 23-tooth-green geared sender, 4.1 having a 22-tooth-red geared sender, etc? Additionally, I found this note: "2004 - Rear end for the 6-speed changed to a 4.10 from a 3.90. This makes the car feel a bit faster at the expense of high revs on the highway." on Reddit (admittedly also not really known as an authoritative font of Miata tech knowledge). I see that you mentioned the 5-speed transmissions, but what about the 6-speeds? Would the 04-05 6-speed yellow sender actually be correct? Are the reports of a 4.10:1 rear end in the 04-05 6MT cars incorrect? Also, if Mazda only used 4.3 and 3.909 for the rear end on NB, why are there four US-market sending units that are identical aside from the plastic gear?

It seems that if you can swap the NA cable into an NB transmission, then as long as you've got an NB sender that was configured with the correct gearing for a 4.1 final drive then you should be able to stuff it in an NA transmission and be good-to-go, right?

Aside from that, the speed sensor from an auto-trans wouldn't work properly in my 1997 5-speed manual transmission would it? The speed sender for the manual transmissions is gear driven while the auto transmissions use a pickup-type sensor, right? Looking at pictures of an A/T sender I don't think that it would even mount properly in the 5-speed manual gearbox?

As for the MS3pro... there seems to be a lag-time between its input and output. (See my other recent thread: https://www.miataturbo.net/megasquir...l-noise-83602/ ) "This kept the VSS signal clean, but the cruise control surged something terrible because of the lag time between input-calculation-output on the MS3." Any ideas on that issue would also be appreciated.

But even if I got any of the NB speed sensors and input them into the MS3pro, I'd still have to condition the signal first since they are a VR signal generator (conversion to square-wave takes place inside the instrument cluster) and it's expecting something along the lines of a 5v square-wave input, correct? And then I'd have to convert the output from a square wave back to an AC-wave in order to feed the proper signal to the NB cluster.

jnshk

OK, after more google-fu I've found a statement that intimates that the 99-00 Australia-market 5MT NBs came with 4.1 final drive rear ends? I'm still totally confused by the lack of documentation and conflicting information out there though.

Mazda USA shows the following senders:
M527-17-400A - 23-tooth, Green - 1999-2005 Miata 5MT, 2003-2005 w/Normal Suspension
M526-17-400A - 22-tooth, Red/Burgundy - 2001-2005 Miata w/ 5MT, Vehicles with Sport Suspension
M528-17-400A - 21-tooth, Yellow - 1999-2000 Miata 6MT, 2004-2005 Miata 6MT
M534-17-400 - - 20-tooth, White - 2001-2003 Miata w/ 6MT

There's a Mazda p/n floating around for the 6MT (3.636) from Australia, but I haven't found one yet for the 5MT from Australia yet. I would assume it's the same as one of the USA-spec units?

So why/what is the difference between the sport package transmissions or rear ends? Or did the sport package cars have different tire size? Why the change in sender for 6MTs from 01 to 02 and then back again in 04?

NiklasFalk

iTrader: (1)

Europe is full of them, all 5speeds had 4.1:1 (as well as some other non-US markets as you found out on your own).

Original Mazda® Tachosignalgeber 5 Gang
Completly unsure if the pictured colors are correct though (Red 22teeth), the USD is strong now...

Not enough info to see if it's the right one (but it's a red gear)
MAZDA MX5 MK2 MK2.5 GEARBOX SPEED SENSOR | eBay

BTW IL picture a light blue gear with 19teeth for use with the 3.636 (6sp EU).

jnshk

Thanks, for the additional info, Niklas! Can you tell me what tire size was specified for NB cars with 5MT+4.1?

Doing some digging, it looks like NBs were offered with 15" wheels (195/50-15 -- assumed to be "normal" suspension package) and 16" wheels (205/45-16 -- assumed to be "sport" suspension package). The 15" tires are smaller diameter than NA tires and 16" NB tires. Assuming that the UK spec cars came standard with a smaller tire (like the 195/50-15) then it's starting to make sense to me. If that's the case it would go something like this:
5MT+4.3+15=green-23-tooth
5MT+4.3+16=red-22-tooth
6MT+4.1+16=yellow-21-tooth
6MT+3.909+15=yellow-21-tooth <-- Not sure if this combo ever offered, but looks like it may have been based on Mazda's application notes (Listed as being " Built On Or After 4/1/1999")
6MT+3.909+16=20-tooth

Braineack

iTrader: (62)

ms3. it's all the same firmware.

jnshk

OK, got some confirmation on tire sizes offered in UK and that seems to anecdotally confirm my theory, though not entirely as I had expected. Given that new information here is my new theoretical chart should anyone else be scratching their head on this matter:

P/N: - gear teeth, gear color >> trans+rear+tire (year)
M527-17-400A - 23-tooth, Green >> 5MT+4.3+15" (99-05)
M526-17-400A - 22-tooth, Red/Burgundy >> 5MT+4.3+16" (01-05)
M526-17-400A - 22-tooth, Red/Burgundy >> 5MT+4.1+15" (99-00 Euro market?)
M528-17-400A - 21-tooth, Yellow >> 6MT+4.1+16" (04-05, and 14" on Euro NB1s)
M528-17-400A - 21-tooth, Yellow >> 6MT+3.909+15" (99-00 Euro market?)
M534-17-400 - 20-tooth, White >> 6MT+3.909+16" (01-03)
M533-17-400A - 19-tooth, Blue >> 6MT+3.636+16"/17" (Australia market only)

Of course this is still based on anecdotal information and not clear documentation, but it seems to match well with Mazda's fitment notes as well as accounting for some of the more commonly tossed around wisdom.

bbundy

for the NA this is what works for me. cant get a 21 or 24 from mazda that I can find. I got those from Chikara Motorsports. Muruha

20t =3.636
21t =3.909
22t =4.10
23t =4.30
24t = 4.44 -4.7

jnshk

Thanks for the additional input! I think this may also be where some of my initial confusion was stemming from because I was seeing references to driven gears for the NA speedometer cable as well as the NB pulse generator.

Can I assume that those gears are aligned L-to-R with fewest-to-most teeth?

It will be interesting to see what kind of speed-decoding I get once my sending unit arrives. Even if I ended up getting the wrong one, at least that will be a slightly more definitive data point.

EO2K

iTrader: (37)

Wait, then why the **** did I buy a 3.63 sender if my MS3 can do this internally?

jnshk

Well, you can do it, but I'm not sure how straightforward it would be. To do it correctly, it's not as simple as just 1-wire in 1-wire out. The NB sender is a VR generator that sends a deformed sawtooth AC wave current to the microcomputer in the cluster on two wires, which then converts it to your speed/odo and a single-wire 5v squarewave output for your ECU and cruise control. So you would need to build a circuit for your VR input, and then need to convert the single-wire squarewave output from the MS3 back into a two-wire AC wave signal. Check out this thread: https://www.miataturbo.net/ecus-tuni...details-73810/

Also, while it may be something isolated to my particular unit or install, I found the lag time between signal input and output to be a potential concern. It was enough to cause a severe oscillation (surging) in the cruise control on my 1997.

ridethecliche

iTrader: (2)

Bumping this to see where folks are changing the values for VSS in tunerstudio to get the megasquirt to adequately compensate for a change in rear diff ratio. I'm swapping diffs soon and it'd be awesome if I don't have to get another speed sensor.

jnshk

Not sure if you ever got your answer, but: Advanced Engine > Speed and Gear Sensors. If you have an NB, you can route the VSS from the sender to a VR conditioner and into the MS3 (or possibly direct to the MS on a VR conditioning input), then configure your VSS out and wire it to the speedometer/odometer on the gauge cluster. Although the speedometer module is expecting a VR signal, I've read that people have used a square-wave signal like the MS outputs and it is supposed to work just fine. If you have an NA, you'd have to switch to swap speedometer gears or convert to a cluster with a digital speedometer because the NA speedometer is cable-driven (and actually generates the VSS output).

Here is a screen shot of the Speed and Gear Sensors settings on my MSPNPP '91 car.

VSS Input/Output settings.