Gear Noise on Overrun

[jondee86]

AE86/4AGE/T50 and I get a lot of gear noise on the overrun in all
gears. Under acceleration the box it quiet and changes sweet as both
up and down. Any suggestions as to why it would be so noisy on the
overrun ?? It is the same sort of noise you get when a gear has lost
all it's hardening and is pitted to hell... ugly gravelly noise

Is there a thrust bearing in there that only loads up on the overrun ??

Cheers.... jondee86

[sergei]

I got similar in my ST205 box, I don't care about noise (my ST165 doesn't have any sound deadning what so ever), but my concern is if I soon will need to order new box or not?

[NZ_AE86]

Is this a new problem or just started?
Do you have a sprung centre clutch or solid centre?
Do you have a factory gearstick, cut and modified or TRD shortshift?

[jondee86]

This car has been off the road for a looooong time. First thing I did
after getting it running was to get a new custom 2" exhaust fabricated
as I changed from cheap extractors back to the stock cast iron exhaust
manifold. I also fitted the brace that goes from the 2>1 section to the
bell housing.

Yesterday was the first serious dry weather run Today I went out
again and took more notice of what I was hearing, and when. Nearest
I can figure is that there is some resonance/vibration being transmitted
from the exhaust to the bell housing (particularly between 4-5000 rpm).

This comes in on top of the normal gear noise and makes it seem like
the gears are rattling. The clutch disc is sprung centre and everything
else is stock. So it looks like it is not a gearbox problem at all

Cheers for the replies..... jondee86

[matt dunn]

I have struck this in a few cars, but only with solid centre clutches.

On decel the load on the gears is reversed, so the car is turning the engine,

Each time the engine fires a cyl, for a second they force changes back,
so the engine is driving the car, then back again.

This causes the gearbox teeth to chatter on deceleration.

My EVO that i had did it as soon as the clutch went in,
sounded like an exhaust rattle,
and a month later I put a std plate back in it and it went away.

It may be part of your problem,
maybe not.

Matt

[sergei]

I have TRD clutch on mine but it is defently srpung one...
It sounds exzactly like you describe it.