Noisy gearbox

[sjl1]

So i have had my 310r sigma for a couple of months now and its settling down nicely but my biggest issue is the terribly noisy (mx5) gearbox. When Caterham did the engine upgrade they said it was normal and to be fair, the courtesy cat they leant me wasnt much quieter. Its a grindy rattly whine on the overrun worse and worst in fourth. I also notice the gearchange isnt great and crunches into 2nd when cold, improves once warm. I suspect all of this is 'normal' but my question is does anyone have any suggestions on how to improve things? its ruining my enjoyment of the car

[ScottR400D]

You sure it's not the normal diff noise? That's usually more noticeable in the higher gears, IME. 

I notice a little gear noise in my 6 speed, other than 6th, but it's not loud, nor rattly, just normal gear noise. 

[SM25T]

Assuming it has oil in it (!) ..... A new Mazda gearbox shouldn't be noisy.

[sjl1]

Definitely not the diff, which is a BMW LSD unit and has a reputation for being quiet, noise comes from front lhs of gearbox and is worse from passenger seat

The mx5 gearbox does however seem to have a reputation for being noisy, it sounds like layshaft rattle on overrun and the courtesy 310 i borrowed was not dissimilar, very noisy, both have light flywheels

Oil? When i bought then car the previous owner had missed adding the top bush on the gear linkage, causing it be be sloppy, when i lifted the levers cover to fix this it was full of oil, although i understand this is a separate housing from the main case so not completely conclusive. I suspect it would have seized by now if it was empty, i drive it in the manner intended.

[mossy7]

A 310R has the limited slip dif and the same setup on my 7, ( LSD, 5 speed, Sigma.) is also noisy, worse in 4th,rattly and awkward to drive smoothly with lots of back slap if you are not careful. My 5 speed is also difficult to get into 2nd when cold and much better when warmed up.

They all do that and I reckon it's part of the character and the fun.     

[Duckpit]

I once put the wrong oil in my Type 9 and the noise was horrendous, put the correct oil in and it went back to being nice 

[Jim 123]

It might be worth checking the oil level in the main case given your comment re the previous owner.  

On your car the level plug should be accessible from the LH footwell where there is a large diameter hole and grommet to enable access. The plug has a square head, not to be confused with the hex head bolt just below it.

[sjl1]

Mossy - whilst i appreciate these cars have 'character' this gearbox is far noisier than the type 9 in my old K series to the point it spoiling the experience. Your cars character sounds very similar to mine

Jim, thanks for the suggestion, i think i have some spare oil from previous car and will check the level as you suggest, had forgotten the location of filler has changed

[ScottR400D]

The BMW diff has a reputation for being quiet?! That's a good one!

In a BMW maybe but not in a Caterham. It clunks and chatters with the worst of them. 

Your gearbox isn't touching the chassis is it? The clearance is tight. 

[sjl1]

Scott, noise is only on overrun which makes me think it internal noise, but its a good suggestion and got to be worth checking when im down there checking the oil, thanks

[ScottR400D]

I understand that the Mazda box has less clearance than even the 6 speed and I would think it's easily possible for it to be fitted to be touching somewhere which might amplify the sound and transmit it. If, by chance it were touching on the left that might explain why it seems worse on that side. 

[sjl1]

Thanks for all the suggestions, planning to take a look tomorrow after work, hopefully will check oil level and too up plus check clearances, wish me luck

[EEK]

Sorry wrong thread

[ChrisC]

I accuse my 6sp BMW LSD combination of being noisy in my 360R.

Initially I though it was the gearbox, but the more I think about it I think it could be the change in spec made to the LSD diff oil.

Caterham are now using the Motul 75w140 Competition Gear oil recommended by Titan (the LSD manufacture) instead of 80w90 GL5 (with an LSD additive) which I assume is the recommended BMW oil.    I suspect this change is generating the noise.

It would be nice hear from an non 'R' owner that has an open diff, what their experience is. 

[sjl1]

Well found the drain plug, opened it up and it was full of oil, plenty on the floor by the time i had stuck my finger in to check the level. Looks and smells like the right stuff, not smelly enough to be diff oil.

Also lifted the tunnel cover and no sign of gearbox touching frame, about 1/8 inch away from lhs chassis diagonal, cloae but no witness marks on chassis. There is a bulged panel on this side of tunnel providing room for the box which i cant get to, i need a strip of plastic to pass down and test it. If the gearbox did kiss this bulge it would make a great amplifier so this needs more looking at. I am tempted to loosen the gearbox mounting bolts and try levering it sideways

More to do

[Jim 123]

If you still suspect some contact it is maybe worth a check for touching between the LH chassis longitudinal upper edge that forms the transmission tunnel, and the box casing in the area to the rear of the filler plug. Things can get tight in that area.

[ChrisC]

Was the oil blue?  If it's blue then it's the Motul stuff..

[ScottR400D]

I have Redline oils in both the box and diff, after the original Comma products. 

Apart from a slightly slicker change, there no discernible difference IMO. Certainly haven't notced any reduction in diff noise/chatter. 

[sjl1]

Thanks all, oil is clearish yellow and, not blue or red, i think my gearbox change is normal from what all describe, notchy when cold, improving when warm, was similar to courtesy 310r car

Noise on overrun is also 'normal' but still hellish loud, im kinda hoping its being exacerbated by contact between box and panels but realise its a longshot, still worth a go. Am thinking of lossening gearbox mounting bolts and prying box over to the right to maximise any gaps.

[tangomikeromeo]

FWIW - are the prop's nipples greased?

Caused similar symptoms for me.

(if you can read that and not snigger here post something funny/smutty/engaging in chitchat please. It's dull when we're mostly out driving over there)

[sjl1]

propshaft  uj's have oil fling around them but can check again

investigating gearbox clearances highlights its very tight on lhs, less than 2mm in places which seems very close, cant image it doesnt vibrate against chassis with these clearances, next step seems to be loosening gearbox mount and trying to pry it over to rhs a bit

[sjl1]

So took car out for a good run today and decided gearbox isnt touching chassis and noise is only on the overrun in fourth, doesnt do it in other gears. Also change improves substantially once gearbox has warmed up. Conclusion is all is well but its still noisy

 

So my question to blatchat is does anyone have experience with using other gearbox oils in their MX5 boxes?

[Jim 123]

FYI re oils, the gearbox comes pre-filled in the kit.  No idea what the original fill is, but Caterham also supply a litre of Comma 75W-80 GL 4 for topping up.