- My model of MX-5 is: NA Eunos 1.6 1989
- I’m based near: North East London
- I’m looking for technical help or recommendations on: I have had a new
Clutch, Genuine release bearing, Spiggot bearing, RMS and Gearbox seal recently done.
I changed all the fluids 800 miles ago in late February.
Since the new parts have been fitted the release bearing seems to make similar to slightly more noise and the gearbox seems to whine, which is new. Reminds me of driving a Triump Vitesse. The release bearing has always made a noise, hence refreshing the whole system while dropping the gearbox.
The release bearing noise is loud when in neutral and went you press the clutch it goes. Now the gearbox whine is a lovely new addition…
Any ideas or thoughts…The mechanic has now dropped the gearbox twice and I want to move on as it’s been done as a favour.
Not super technical but is the main shaft worn…? Why is the gearbox suddenly whining. I have read there is slight adjustment that can be done on the gearbox…65mm ±5mm on bottom of gearbox to chassis rails.
Any feedback or thoughts appreciated.
Theo
Sorry to hear about your troubles, I’ve changed release bearings before with a new clutch and they’ve been noticeably noisier than the old ones. I remember resolving that with an OEM Mazda release bearing. The NA/NB boxes are very sensitive to the type of oil, the old Ford Motorcraft stuff used to make a big difference in slick gearchanges. In addition the propshaft angle can make things noisier if the PPF height to bottom of gearbox is not set to about 60mm. (some manuals say 56mm, some 65mm) This can make a difference to noise but it’s more likely to be a combination of things - oil, angle, bearing etc. Have you replaced the lower & upper gearchange rubber boots? a hole in the upper one can let through a surprising amount of noise.
Hello Carl,
Excellent feedback and nice to know someone has had past experience and resolution around this issue.
I found this video with goes through about adjusting the PPF and gearbox. Still can’t see how this is adjusted, even from the video. Might try and take a proper look under the car on Friday or speak to my local garage about this issue. Jump to 5 mins 30 secs, can’t believe how clean his car is…
Good idea about replacing the lower and upper boot…did that on my last NA. 
Regarding the Ford Motorcraft oil this is mentioned a lot on the American websites. Would you happen to have a link to a retailer as I can see it is hard to obtain in this country?
Many thanks,
Theo
Theo, to adjust the ppf clearance take a look at about 6 mins on th video you can see him pushing the tail of the gearbox up to add the black support bracket. If you’re adjusting when the gearbox is already installed you need to support the tail of the gearbox with a jack, then loosen the two left big bolts plus the support bracket right bolt - don’t remove them… The tail should then be able to move up and down an inch or two like the video. Run a straight edge across the chassis rails and measure the 60mm. I used to use a metal ruler with some tape wrapped round it at 60mm so I didn’t have to scrabble around with a torch under the car!
What the measurement is doing is setting the prop shaft angle so it’s not too severe and doesn’t put strain on the UJ.
The Ford Motorcraft oil I used to buy on US eBay but not bought it for a while sorry. - Edit just checked on US eBay and the Motorcraft stuff is stupidly expensive now! People on Miata.net seem to be recommending Redline MT90 gl4 fully synthetic now as being just as good, plus it’s a lot cheaper and you can buy it in the UK.
Whatever you do make sure you take the refill bolt out the gearbox before draining it because sometimes they get stuck. If you find this out after you drain the box you’re going to be stuck with an empty box 
I remember when Friday nights use to be going out with friends…anyway I measured the original distance 53mm…I tried to set to 67mm but it settled at 64mm. Will test in the coming days.
Thanks Carl for your assistance
