NB Gear Selecter/Shifter Question.

[CheyneX5]

Hi all,

As of yesterday, I now have an NB8A 5 Speed in my NA6.

When I picked up the car, I noticed that the gear lever was slightly tilting to the right, it's not a massive tilt, but it is noticeable. It can be corrected by moving it back into place, but once I let go, it will just move back.

The mechanic (mx5 factory) said that they only had the one NB shifter in stock and they could not try any others to see if it would be different.

My question is: Is there a difference between an NB8A shifter and an NB8B shifter. Apart from the obvious of the extra gear in the 8B, does the shifter actually change at all and could they have fitted the incorrect model?
Or... Maybe it just has a small bend or is broken somewhere in the join.

Thanks.

[manga_blue]

Cheyne, I've just changed from an NA to an NB8A 5 speed this week. I reckon the shift levers sit in exactly the same position. The detent springs in the change control system should hold the lever exactly in the 3rd/4th plane. Can't comment on an NB8B box though.

The main difference between the NA and NB8A boxes is in fact in the change control system. Part of it is outboard in the NA, in the NB it's all inboard. The NA shift lever has a single notch to help locate it in the extension while the NB one has a double notch. Generally I'd say the NB shifter is clearer and more positive in its action and probably tougher.

[CheyneX5]

Thanks for the reply Phil.

Did you notice that the Shifter turret sits slightly more to the right and slightly further forward? It would only be by a few mm. I noticed this as there is more tension on the leather shift boot when entering 5th. And the rubber boot below makes a pop noise when coming out of 5th.

The mechanic says this is normal as the design is slightly different, however my gear stick is actually on a tilt to the right by a few degrees as well.

Might it be worth trying to source another shifter?

[manga_blue]

I didn't measure but I assumed the turret was in the same position. At least it looked that way.

When tightening up the PPF I levered the box around a bit so that the turret was centred in the hole through the transmission tunnel. It was out to the left by about 15mm (ie opposite to yours) and fell dead centre fore and aft. I doubt I would've been able to do anything about the fore/aft position anyway without moving the engine mounts.

I'm not sure what you mean about the shifter sitting a bit to the right. When mine is in neutral the shifter is being held very firmly in the 3rd/4th plane (ie exactly mid-way between 3rd and 4th) and it's 1 deg to the left of vertical fore/aft. This may be the first time anyone has ever put a spirit level on a gear lever. Anyway it's much firmer than the NA one ever was.

Are you saying:
- your shifter is in the 3rd/4th plane but the top is now sloping more to the right than it used to, or
- it's sitting somewhere between 3rd/4th/5th/reverse?

If the former then is the top of your engine also sloping a bit more to the right? That (together with the fact that it's also sitting a bit further forward) would lead me to ask the question "Has the right hand engine mount been broken?" The engine can get shaken and pushed around a bit during a gearbox job.

[CheyneX5]

What you say about engine mount did cross my mind, but everything feels relatively fine...

What you said first about the stick is what I am experiencing, the shift knob just tilts to the right a bit.

Here are a couple of pics showing the issue. Firstly, this is how the turret sat with the old NA box:



Now this is how it sits with the NB box.



Also, this is it in 3rd gear:



And in 5th:



Do you think it's possible that the gear box was mounted incorrectly? Or that the engine could have moved slightly during installation?

I have no idea honestly, it just seems strange that one would fit perfectly, then the other fits weirdly, even though, minus a few design alterations, they are the same gearbox...

[manga_blue]

Bloody hard to have the engine and gearbox at different angles. There are two dowels at the back of the engine which locate the bellhousing onto it. I can't believe anyone would either remove the dowels or not bring the bellhousing flush against the back of the engine.

The left/right positioning of the turret is set wrong. They need to loosen the 3 PPF bolts under the gearbox and lever the back of the box until it's properly in place before tightening the bolts again. It looks about 20mm out which is way too far. Similarly there's a dimension spec for the height of the box, it should be 60-72mm from a straight edge held against the chassis rails to the bottom of the PPF between the front 2 bolts. Having either of those wrong can lead to drivetrain vibrations.


The 2 engine mounts are always stretched during gearbox work. Without the gearbox attached the engine just balances on them. It would be normal to rock the whole engine back and forth at least 10 degrees while pulling/fitting the box.

Sent you a pm.

[CheyneX5]

So, you are saying the turret has some adjustment in it?

[manga_blue]

Let's say a straight line from the front of the crankshaft to the pinion of the diff is the plumb line. With the gearbox end PPF bolts loose you can swing the back of the gearbox at least an inch or two in all directions from the plumb line. My reading of Mazda's 60-72mm specs is that they want the output shaft of the gearbox to be no more than 6mm from the plumb line. It takes 5 minutes to position the gearbox and then lock it in place by tightening the bolts again.

What happens if you put a spirit level across the tops of the cam covers?

[CheyneX5]

Ok, that makes more sense.

I'll try the spirit level trick tomorrow morning on a flat surface. But I think I will just take it back to the mx5 factory tomorrow morning and get them to fix it.

[koop21]

Not sure if this helps but i managed to put my 6spd gear shift in "backwards" and it had the same issue your experience with the 5/6/R in my case very far right.
Maybe rotate your shifter and see if it makes a difference?

[manga_blue]

It's possible, I can't recall if the lever is straight or not. So far we've been mainly thinking about why the gearbox is not in the same spot it used to be.

[CheyneX5]

So,

-alex kindly donated her standard NB8A shifter. I installed it in the gearbox and now it feels and sits perfectly.

What was the problem, the shifter that was originally installed had a big fat bend in it.

I'll update this once the gearbox has been remounted as its still at the mx5 factory.