Should there be anything loose inside of a gearbox?

[damesta]

I have a rattle noise that I'm 90% sure is coming from the gearbox. It sounds like an inconsistent rattle of something hitting the housing on the inside, it is not a steady tap. The car shifts fine, no grinds or anything but I don't aggressively drive or shift hard/fast since I've noticed the rattle either. So I ordered some shockproof lightweight to see if that would help and I drained it today, the plug is full of the expected shavings but nothing big, and the oil looked relatively clean while draining. I have a little wire feeler that I stuck up through the drain hole to feel around for any debris and found nothing...but about 6-10 cm behind the drain hole I found something loose that I can make move by pushing on it with the wire feeler and I think I can hear it tapping the housing if I push it back and forth. It is not completely free, it won't move around where I can pull it out or anything but it is loose enough to easily move up and down to tap the the gearbox housing by just pushing it lightly with a piece of wire. Anyone know what this is? I assume it shouldn't be loose like that but I don't understand why it hasn't caused any drivability issues.....time for a new tranny or rebuild?

Edited May 20, 2021 by damesta

[Duncan]

With any luck that fragment will be magnetic. just use some short wire with a magnet on it to try and drag the part out....but bottom line is nothing should be loose in there so a teardown is in order.

[damesta]

19 minutes ago, Duncan said:

With any luck that fragment will be magnetic. just use some short wire with a magnet on it to try and drag the part out....but bottom line is nothing should be loose in there so a teardown is in order.

Thats what I figured, I have never opened one of these boxes up but I didn't think anything in there should be moving that easily. I was trying to explain as best I could but its not a loose fragment and is not freely bouncing around in there. It is still loosely attached to something (or possible sitting in an area tight enough to prevent it from moving anywhere), I can push on it with my wire lightly and move it up and down to make it do the taping noise, but I cannot freely move it around to where I can get it out.

[Shoota_77]

I'm trying to think what could be reachable through the drain hole and nothing springs to mind.  Everything is pretty solid in there normally!  If it was a snapped off shift fork you would well and truly know about it!

Have you got a multi-plate clutch?  They're generally a pretty consistent rattle but if it's getting a bit old it could be sticking then releasing.

These are pics of my box in bits and there really doesn't look like there is anything that could be flapping around in there (to the right of the centre plate in the first pic and to the left of the plate in the second pic)-

-

 

[damesta]

27 minutes ago, Shoota_77 said:

I'm trying to think what could be reachable through the drain hole and nothing springs to mind.  Everything is pretty solid in there normally!  If it was a snapped off shift fork you would well and truly know about it!

Have you got a multi-plate clutch?  They're generally a pretty consistent rattle but if it's getting a bit old it could be sticking then releasing.

These are pics of my box in bits and there really doesn't look like there is anything that could be flapping around in there (to the right of the centre plate in the first pic and to the left of the plate in the second pic)-

-

 

I don't see anything but not the best angles, the area I'm talking about is pretty much right where the bellhousing meets the center plate on the very bottom...its just out of reach for me to touch with my finger through the drain hole but it moves very easily pushing it with a wire. Even if something was supposed to be loose like that in there it shouldn't be loose enough to tap something else and make a noise. Its crazy to me that this tranny shifts normally like this and hasn't torn itself up yet.

[Duncan]

my bet is it is something small and loose but hard to move because gearbox oil is very sticky....Lots of little pieces that could detatch and have the box still working OK like a synchro clip

[damesta]

4 minutes ago, Duncan said:

my bet is it is something small and loose but hard to move because gearbox oil is very sticky....Lots of little pieces that could detatch and have the box still working OK like a synchro clip

Probably right....so here’s what I’m thinking. Since it shifts normally and I haven’t noticed any grinding or drivability issues maybe I can save this tranny. I think I’ll drop it out and pull the bell housing so hopefully I can get to the loose part and either remove it or fix it if it’s a clip or something. Then hopefully reassemble and reinstall.

[hardsteppa]

Might be the drain flap at base of the centre plate. It moves, but shouldnt make any noise

[damesta]

7 hours ago, hardsteppa said:

Might be the drain flap at base of the centre plate. It moves, but shouldnt make any noise

Hmmm, does anyone have picture of this flap so I can visualize it? I searched but don't see a flap anywhere on any skyline center plate pictures I could find. But yes, that is exactly what it feels like, would be bottom center of the plate, feels like I am lightly opening and closing a hinged flap with the wire, the closing making the taping noise when it makes contact....could be that I can only hear it because it is closing faster/harder due to the transmission being empty right now.

Edit: Found a picture of an os giken gtr center plate with the flap intact, some of the other plate pictures I found of rb20/25 center don't have the flap intact but the hole for it looks lower and more centered than on the gtr box. I'm starting to think this is what I'm hitting, looks like it could move in and out a few mm and make a tap while there is no oil to cushion it. 

Edited May 21, 2021 by damesta

[GTSBoy]

Buy eBay $25 USB inspection camera. Poke through hole, inspect. You'll never regret spending the tiny amount of money.