redline transmission oil problem

[blackster]

I have recently changed my clutch on my NA 1.8 , ever since then I have heard a noise at idol from the gearbox like a humming bearing noise. When you press the clutch in it disappears. You can hear it in 1 st gear on take off too.
It theory it can only be a bearing on the input shaft as nothing else spins at idol.
I have had the box rebuilt by mazda all bearings and synchros. I have replaced the thrust bearing.
It cant be the spigot bearing because that doesn’t spin at idol with foot off the clutch. The only common thing is the red line oil in which I have reused because it was new.

Am I over filling the box
What oil should I use.
maybe the grade of oil is wrong.
Any suggestions

Cant comment on the exact nature of the problem, but from what I've seen re-using the same gear oil even if its only been in for a month or less, will still get metal bits floating around that might not be quite visible to naked eye.

Im more then happy to recommend redline lightweight shockproof, its made a noticeble difference for my 5 when the box was cold on startup and even better shifting when its warm.

[Babalouie]

Me personally I prefer a thicker gearbox oil to the Redline (I also noticed that the box was noisy). Something more like 75/90W and Royal Purple MaxGear is what I use in mine...

[Russellb]

In theory it can only be a bearing on the input shaft as nothing else spins at idol.
The only common thing is the red line oil in which I have reused because it was new.

Every thing Except the output Shaft is turing inside the box (Costant Mesh Gearbox)
so could be 1 off 9 bearings making the noise
I have always run Penrite 75/90 in my car with out a problem
I have done 45 0000Km in it and the last 7500km it has been turboed
I also am very hard on Gearboxes. At the moment it has 215 000km on it an still feels fine and no funny Rollover noise

[JBT]

I have recently changed my clutch on my NA 1.8 , ever since then I have heard a noise at idol from the gearbox like a humming bearing noise. When you press the clutch in it disappears.

Sounds to me like noise from the throw out bearing.

[Sheck]

I've got the same thing from re-useing the redline oil in my gearbox!!

Hrrm might have to fork out for another big bottle of it
$110 for a gallon

[CT]

Did you replace the throw out bearing as well as JBT said? But, Castrol make a specific oil for the 5 speed mazda gearboxes. It's the onli gearbox oil the racecar see and it's never given any trouble at all.

[trader]

Half the problem with redline appears to be the information available.
I bought it for my NA 16. I went in to get the MTL after reading about it here but was told that MT-75 suited the MX5 better. I got home and halfway through pouring the second bottle in I discovered the shop had given me one bottle of MTL and one of MT75! Too late to take it back but got the supplier to contact the importer who said that it would be okay to mix it. If you look at Okibi's pics on the 'transetdiff oils\" thread you can see how similar the bottles are. The information on the label is almost word for word! Its not winter so I dont know how effective it is on cold mornings, but at least I dont have to change it as often.

[bigdog]

I am not in any way connected to redline, so not wanting to grind an axe or anything, but the oil they recommend for MX5 gearboxes (ALL models) is MTL Lightweight Shockproof which is a 75W90 weight oil, so Babs your problem is not 'thickness' if you swapped for another 75W90.

Silverback the problem could well be the throwout bearing - I have had similar problems in the past with a new bearing being 'dry' and noisy straight out of the box.

[Babalouie]

I am not in any way connected to redline, so not wanting to grind an axe or anything, but the oil they recommend for MX5 gearboxes (ALL models) is MTL Lightweight Shockproof which is a 75W90 weight oil, so Babs your problem is not 'thickness' if you swapped for another 75W90.

Silverback the problem could well be the throwout bearing - I have had similar problems in the past with a new bearing being 'dry' and noisy straight out of the box.

...could be that I was given the wrong grade...it was electric blue, and weas very thin. The Blurb on the back said that it was "equivalent to a 10/30W oil" and it felt it.

[JBT]

Yep replaced the throw out bearing or otherwise known the thrust bearing. But the noise is at idle and the trust bearing is not in contact with the pressure plate at idle. When you press the clutch the bearing pushes on the fingers of the pressure plate so its not that one.

Yep, I know how a throw out/clutch release bearing works. They can rattle/rumble in neutral with foot off clutch pedal and then stop it as soon as the pedal is pushed. The noise goes away because a load is put on the bearing. I'm still putting my money on this being the culprit because the noise only started after you replaced the clutch etc.

IMHO, if it's not the TOB/CRB, then it's the spigot bearing (they normally squeal though) or worn/noisy gearbox bearings.

There is another remote possibility that the contact point between the slave cylinder pushrod and the clutch release lever needs a dob of high temp grease on it.

[CT]

Yep replaced the throw out bearing or otherwise known the thrust bearing. But the noise is at idle and the trust bearing is not in contact with the pressure plate at idle. When you press the clutch the bearing pushes on the fingers of the pressure plate so its not that one. I will try a slightly thicker oil what is the castrol oil for mazda boxes called

VMX or something similar. Why not go to stupidcheap and check them out for yourself. It actually says on the front or the back "for Mazda 5 speed gearboxes". Its the one mazda actually recommends for these boxes.

For the record, a thrust bearing is a type of bearing which uses balls supported in a ring. A throw out bearing is a type of thrust bearing which is used in the clutch release mechanism on a car.

[bigdog]

What JBT said. I actually bought a car very cheaply once by convincing the salesman the gearbox was shot, having guessed it was the throwout bearing They can make quite a lot of noise just sitting still - often because they are able to just touch the fingers of the pressure plate without any pressure (which stops the noise). Having said that, re-using oil is not good practice, and it is possible that having done this you have introduced contaminants to the bearings. Was the oil re-used before and after the new bearings etc? If so then you may be looking at a strip down to check for damage.

As far as oil grade goes you should only be using MTL Lightweight Shockproof from Redline, or a similar oil from Castrol/Motul etc in 75W90 weight. Anything heavier is likely to cause problems - poor cold lubrication on start up as the oil is too thick to force between the teeth. Lighter oils will cause premature wear as the oil doesn't maintain enough 'thickness' at higher temps. There is no need to run expensive gear oils in an MX5 if your box is working well - they are no more or less complex a gearbox than many others out there, and most boxes are fine with good old Castrol 75W90. I only used the Redline to improve the quality and feel of the shift in my 6 speeder, and it does that very well.