WTF do I have? (Question/rant thread)
 

I have a (I think) standard 5-speed box. And what I thought was a stock 4.10 rear-end. BUT ALAS, it is not so. One of them is off.

In terms of top speed of my car's gears, I have:
1st ~30mph
2nd -55mph
3rd -80mph
4th -100mph
5th -?

RPMs at 65mph in 5th are ~3,500, maybe a little more.

Anyone recognize this gearing? Every single speed calculator I've ever used has told me that I do not have the gearing combination that I think I have.

Stock tires.

EDIT: On another note, why has no one cryo-treated the stock 5-speed as opposed to getting a 6? Is it more expensive? Negligibly stronger?

looks the same as my 5sp/4.30.

I keep punching that in and it gives me 4th gear top speed of 110mph @ 7,000rpms. I have GPS confirmed 100mph @ the top of 4th.

A 4.44 diff ratio gives pretty much exactly what I have... Hmm...

Correct me if I am wrong, but the 6speed case is reinforeced much more than the 5speed giving the internals proper contact with higher torque levels. (?)

However, those quaife gears use the stock 5speed gear box correct? hmm

Don't know what you have and when I topped out 4th I NEVER took my eyes off the road enough to verify the exact speed, but your 1-3 are exactly the same as mine.

Its reinforced and the gearing is closer meaning less stress when shifting from gear to gear.

That in itself is already a big contribution to the strength IMO.


Cry-o treatment really doesn't help much. again IMO. different tooth design as well as closer ratios will improve torque capacity much more

Confirmed speed with GPS? They seem to all be ~3-4mph short until 4th. Going by year, you should have the same 5 speed and 4.10s as the rest of us 1.8NA guys.

tire size?

check for a 6th gear?:giggle:

I bet your tachometer is off just like everyone elses; check your rpm in tunerstudio while cruising.

(or are you hitting fuel cut while determining your top in each gear?)

my vote is for tire size.

Jack the car up, and count how many times your tires rotate for 1 turn of the driveshaft. It's a whole lot safer and easier than driving on public roads at those speeds. (Not that I have a problem with that).

Unfortunately, tire size wont make a difference, so we can rule that out - unless you're getting your speed calculations from a source other than the speedometer.

And I was going to suggest 4.30 when I saw the 3rd gear speed of 80mph. When I had the 4.10/5spd combo, I would see about 85-88 mph at the top of 3rd gear. Looks like someone beat me to this thread!

OP, there's about a 3.2% decrease in speed readings with a 4.44 over a 4.30. There are quite a few things that can help us to say that it is NOT a 4.44.

1. The actual likelihood that you have a 4.44 rear end in your car. A 4.44 was't something you're going to find in a production Miata. US Cars got the 3.90, the 4.10, and the 4.30. It is noteworthy, however, that Mazdaspeed does actually list miata compatable R&P Ratios of 4.44, 4.875, and 5.125 here: http://www.mazdamotorsports.com/pdfs...Drivetrain.pdf

2. The amount of error in your speedometer. Federal allowance is + or - 2% when the car rolls out of the factory. If you are measuring with anything other than your cars speedometer, a change in tire size, tire pressure, tire manufacturer, etc, will change this. It is also important to note that the parts that tell the speedometer needle where to go aren't going to be exactly as they originally came from the factory. Springs wear out, and finely tuned eddy currents change.

3. The amount of error in your tachometer/rev limiter. No explaination is really necessary.

4. Human error. You're trying to get exact numbers out of a speed calculator which gives you 4.44 gearing. Is your speedometer reading exact numbers, or do you have to interpolate what your speedometer is saying? Are you reading on the high side of the 80mph marker, or the low side?

Truly appreciate the responses guys. It's getting an LSD this winter so I can always pull it apart and check :).

Jack up one side, put a chalk mark on the tire as an index, and do the same with the driveshaft. Now have someone spin the wheel one revolution while you count how many times you see the chalk mark spin..... divide the results by two and you have your answer.

These tachs are way off. I could bury the tach with the 1.6 and now shift past 7500 when my revlimiter is at 6600.