mx5cartalk.com

I have an NA6 with the 5sp manual, and 3rd gear almost always grinds when going into it. It happens a lot more on spirited driving, and not so often when cold or when just driving slowly around. The clutch hydraulics are working fine and are well bled, I have double checked the level of turret and gearbox oil (the latter dribbled out when I opened the filler so it might even be slightly over full??). What is left that it could be? Could it just be a worn synchro??

On my old 5 spd the nylon slot bushing on the shifter itself was broken into little bits and make shifting into 3rd difficult most of the time. Not sure where your going to get a replacement bushing though... So a good excuse to get a short shifter

Im pretty certain that Mania sell that selector bush.

I have had two NA6 gearboxes that developed a 2nd to 3rd problem, particularly on the track.

I had fresh fluids, new master/slave cylinders and the components in gear change replaced so the problem was in the boxes. Redline oil helped extend the first ones life a little.

One I had rebuilt by Reliance Automotive in Canberra and John does a modification using some different bearings to make it stronger. That was a nice box, but much more expensive than the 2nd hand replacement. It ended up in Fanta.

In Britney I replaced the original box with a low km import box and it has worked fine for a three hard years, but is now a little crunchy and sometimes refuses to go into 3rd under extreme load (eg out of fishhook and turn 10 at Wakefield), so is now due for a re-build.

Everything on the shifter is brand new (bushing included), and it is a SSK.

Im sort of wondering if it is worth going down the route of a gearbox rebuild or if I should just live with it. Can I ask how much the rebuild cost please?

The 2nd hand box was around $350 in 2010 (low km import).
The rebuild was part of a much bigger job, but it was probably closer to $500, but I can't be sure.

Have you tried Redline or similar oil which improved my first box.

I am living with the one in Britney for the time being to put off the cost for a while and am just being careful on the up-change, particularly at maximum revs. It is not a problem in general driving, but is frustrating in putting together a quick lap.

I have also put in a braided clutch line which improved the clutch feel..

I've got a penrite oil in it at the moment which helped, along with the braided clutch line. I was tempted by a 2nd hand box, but then what if it develops the same crunch, then I've spent $350 to get no where.

mitch_f1 wrote:Can I ask how much the rebuild cost please?

Forumite here mentioned last year that their MX5 GB rebuild cost just over $2k.

... and mine cost less than $400 on a gearbox that I had taken out. All new bearings, check (but not replacement) of synchro cones, straightened a fork, shimming out of a couple of gears to tighten it all up. It pays to shop around. Don't ask me who did it - retired now.