Diff/gearbox noise when slowing down

[Steve]

you sure its not a stone in the rear exhaust or cat heatshield?

[MX5Spares]

The noise "when its hot or whatever" would have nothing to do with the alignment issues .If it cant be tracked correct that's one issue.Noise may be exhaust or something like that .Maybe baffles loose in rear box,heatshield at rear,etc

[Diarmuid]

The noise "when its hot or whatever" would have nothing to do with the alignment issues .If it cant be tracked correct that's one issue.Noise may be exhaust or something like that .Maybe baffles loose in rear box,heatshield at rear,etc

Well the one thing its not is the rear box, as I have just put a new one on from IL Motorsport, and it had no affect on the sound. but maybe further up the exhaust....

[Steve]

is there a cat on your car? There is usually a heatshield on it... give it a (light-ish) tap with something and see if it or stones in it rattle.

Another thing to have a look at is the exhaust to gearbox bracket, its kinda hard to spot unless you are right under the car or shine a light down from the engine bay behind the exhaust manifold's downpipe.

[Diarmuid]

is there a cat on your car? There is usually a heatshield on it... give it a (light-ish) tap with something and see if it or stones in it rattle.

Another thing to have a look at is the exhaust to gearbox bracket, its kinda hard to spot unless you are right under the car or shine a light down from the engine bay behind the exhaust manifold's downpipe.

Yea she still has the Cat but I got a pair of ramps this weekend and I gave the exhaust and cat good auld banging and nothing, I might have a another go and look at that bracket you mentioned, where is that bracket?

[Steve]

its on the side of the gearbox, between it and the exhaust downpipe

[Diarmuid]

Still never solved this and apparently its more common than I thought, there is an 18 page thread here about it with no apparent fix......
http://forum.miata.net/vb/showthread.ph ... 965&page=2

[turismo2142]

Just saw this post now. I've the same problem myself. A mild grating noise which you hear when you lift off throttle while in gear. You don't hear it until the car heats up.

It's defo not a rattle/heat shield issue.

[fez]

I think I may have the PPF issue. I tend to get it when downshifting or using engine braking. Can it cause damage? Is it an easy job?

[turismo2142]

I think I may have the PPF issue. I tend to get it when downshifting or using engine braking. Can it cause damage? Is it an easy job?

The various links above give you a good picture of what's involved. As far as I can tell it's a rather harmless, albeit annoying, problem.

[Diarmuid]

But it's weird, loads of people seem to have the problem but nobody has been able to fix it. Yeah your right it's only when it heats up and mainly only in 3rd and 4th gear. I have nearly everything on my car sorted by now but this unknown is really annoying me.

[turismo2142]

But it's weird, loads of people seem to have the problem but nobody has been able to fix it. Yeah your right it's only when it heats up and mainly only in 3rd and 4th gear. I have nearly everything on my car sorted by now but this unknown is really annoying me.

As far as I can tell there have been some who've sorted it with the PPF alignment but more who have not. So I suppose you'll never know unless you try that. It is a common problem though, of that have no doubt. I only drive my car in the summer and with the top down so I suppose I don't really notice it too much but if it was my every day driver it would drive me nuts.

And initially, like most, I thought it was a heat shield which was loose.

[Diarmuid]

Yeah I thought it was the heat shield as well, but Steve sent on the PPF alignment instructions which I did with Robert (autocheck) and unfortunately it made no real difference.

[turismo2142]

That's a shame. Had Robert not come across the issue before himself? Would a new box sort it? It's not like there's a shortage of them.

[Diarmuid]

That's a shame. Had Robert not come across the issue before himself? Would a new box sort it? It's not like there's a shortage of them.

I don't think so, but from reading the previous link I have seen guys replace gearboxes, trannys, bearings and a load more and it is still there.