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Weighted Miata 6MT Shift Knob Mod

72938 Views 190 Replies 33 Participants Last post by  Teamspeedy


I had the chance to test drive the NC shift knob earlier today. My throws are more confident, less effort and most noticeably...the downshifts from 5th to 4rth and from 3rd to 2nd, are more assuring (the stock knob seems "unsure" in feel when I engine brake, esp from sliding the shifter from 5th to 4rth notch...a feeling somewhat that it might go to 2nd). Essentially, throws overall are way smoother. Also, this solid aluminum/leather NC shift knob is more elegant and sportier in looks and feel in your hand (the buttery smooth semi-matte black leather blends very well to the leather steering wheel, etc and does not look "out of place" vs other shift knobs). It is also as I estimate, substantially 4-5X heavier than the cheaply light, hollow bodied, plastic stock shift knob.

Quality well Made in Japan (for $95, shipped to my door)..somewhat pricey for a shift knob, but well worth it. I am quite happy with this OEM mod. :)
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How easily was it installed and where did you source it from?
I'll be damned if I can find it -- got a part number? :)

And does the top come off to access the retaining clip or bolt, or is it like the VWs where you have to pull the boot and snip a clamp?
Found it... :)

N125-V8-170F, and geesh -- the dang thing just UNSCREWS?! Much easier than my VeeDub....
Ok, so I got the knob. And it doesn't screw on quite as far as the stock one -- by about 1/2" or so.

Out come the digital calipers, measurements taken, and in the next few days I'm going to take a rod of brass I happen to have laying around, cut a piece off, chuck it in the lathe and turn me a nice spacer that will go between the bottom of the knob and the top of the boot. Shouldn't take more than an hour including drilling the center hole for the shaft.

It'll add a nice little brass accent to the shift lever; brass is pretty heavy as well so I'll gain a bit more mass, and it will look VERY custom-ish.

The only problem is that brass WILL tarnish and I have no real good way to lacquer it to prevent that from happening -- at least I don't THINK I do (might have to see if I can find some spray lacquer that will adhere to it.)

Pics when I'm done, I think it's going to look VERY classy.
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ROFL (on the spare)!

Got it turned; need a 10mm drill bit to drill the center hole before I cut it off.

Off to go get one.

This is gonna be purdy; the correct size, by the way, appears to be right around .270" plus or minus a bit. There's a surprising amount of movement (up or down) with one rotation on the knob, so you gotta be pretty much spot-on with the length or you're hosed.

Pics tonight or tomorrow.... whenever I get it finished.
NOW the shift knob installation is done.... :D

The OD of the bushing was cut to match the bottom of the tapered portion of the knob. I considered going ~.100" larger in diameter BUT then I would have had to machine a "cup" to fit the knob bottom and there would be the risk for snags and cuts; as it was I chamfered the corners a bit to take the edge off. It leaves just a bit of a side gap on the boot but there is no play in the bushing or boot with it installed. Looks very, very close to being factory.


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No. It is not any sharper than the factory plastic knob; I deburred the edges and polished the surfaces with 600 grit before cutting it off, then deburred the cut edge (although it is at the top inside the knob where it is not visible.) There is also no motion at all; the bushing does not move in any plane; the spindle is .400 (10mm) and the hole is .407, just large enough for the bushing to drop over it, and when the knob is installed it is held firmly in place.

If I cut another one (and I might) the only thing I would change would be to relieve the center section of the bottom (which is a bit tricky as you have to run the lathe with the tailstock removed; there is a significant risk of the workpiece binding and if it grabs while removing that material you're screwed) so as to allow the bushing itself to drop down over the plastic retention piece that the top of the boot is attached to. That's why the gap is there on the bottom; the bottom of the bushing itself is flat. I do not have a chuck with a large enough center section to allow a full-length feed-through of the workpiece which greatly reduces that risk while doing that sort of "bowl" cut on the face of the work.
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That's going to be too long if you're using it with the Miata knob. The gap between the bottom of the knob and the boot that needs filled is about .340" (+/- a bit depending on how far down you screw the knob)

It would work well with a knob that has threads all the way to the bottom such as a design similar to a simple round ball.
With the spacer UNDER the boot; note that you lose the anti-rotation notch on the boot by putting it there; hold the boot stationary while installing the knob.

Appearance is "as if factory" in this instance; a stack of fender washers of the appropriate thickness and with the correct-sized center hole would likely work fine since when the knob is installed they're under enough compression to keep things from moving around. There is enough boot room for this to work fine without causing the boot to come taut in any of the gear positions.

Also, be careful not to overtighten the knob if you do it this way -- that retention piece which is part of the reverse lock-out protection spring is plastic and you could conceivably break it.


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10mm, which is almost-exactly .400" A 3/8" (.375") will NOT go.
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BTW if anyone is wondering if I think this changes the feel of the shifting materially - it does.

By quite a lot, and all in the positive direction.
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Well well..... Cut that off cleanly to the correct length and under the boot she goes. .350" should be about right (you can always sand it down a bit to make it shorter and/or to correct a bit if your cut is not exactly straight...)
Junk? You mean just because you're going to throw it away? Well, ok, you could do that -- but do put it on the inside of the boot -- it will look like hell on the outside.
The inside arrangement looks 100% stock (pic above); no binding on the boot at all. I'm torn between that and the external, "has nice brass accent" look.
I put the spacer under the boot, yes. I'm not sure if I prefer it there or on top; I'm going to drive with it this way for a while, ponder the chunk of rod sticking out of my lathe's chuck for a bit as I contemplate the several hours (instead of one) required to turn a TAPERED external spacer (which IMHO would be THE boss item, but it's a HELL of a lot of work on a lathe with only a LATERAL powered feedscrew) and then decide whether I'll leave it like this or go turn myself said tapered external brass piece.
Well, yeah, I could do that I suppose.... but it would probably end up with a step in it, which would be kind of a bummer.....

There are times I wish I splurged for the PCM-controlled feedscrews, but..... oh well.
1. Open the parking brake boot and unzip it.

2. Remove the shift knob.

3. Open the console lid and there is a split inside at the top. Lift the top straight up. You won't break it -- pull. It will come loose. Then work the shift bezel off (it's attached) and the rubber mat that goes into the cubby will come with it. All come up and off.

There you go. When you put it back make sure the tabs align and just press it back down; it will snap back together.

Take about 30 seconds to get to it.
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3/8" is too small by a fair bit -- it will not go on the shaft.
I still have my spacer under, and it's the custom one. I kinda of like it there.
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