Unknown part in TH400 oil pan

Hi,
We found this part laying in the TH400 oil pan of my 400 Automatic. The pan was just opened to change its gasket (which had become porous). No other part of the gearbox was touched.

We do not know if this is a part of the TH400, we could not find an exact match for it in the documentation (Ferrari manual 157/78 for this gearbox or the general TH400 documentation).

It is a small item, made of steel:

Weight 14.6g (0.515 oz)

Overall length 20.06mm (0.7898")

Outside Diameter 15.1mm (0.5945")

It has a small hole on the side 3.4mm (0.134") diameter and approximately 2mm (0.078") deep.

Inside Diameter 10.7mm (0.421")

One end has a face with a 5.24mm hole and a trace of rotation which left a mark on the steel.

The gearbox seems to be operating normally in the garage (low speed) after replacing the gasket and filling the box with hydraulic oil, this mystery part left outside. We have not had a road test done yet.

Any idea if this part is really from the TH400?

Thanks.
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Thanks for all the responses, I gather that this item must have been left in the oil pan from the last oil change (before my time as owner). I am trying to join the Corvette forum as suggested by Sunracer to confirm.

 

Thanks. For the time being, it is almost certain it is not a GM part. There is a possibility it is a spacer in the rear servo, but we have to open and go look in that place. I will post when this is done.

 

The same piece was found in the oil pan of another TH400 (from a 400i Auto), please refer to the picture attached. Here are a couple of things I have been told about this item:

1- It is not a GM part
2- It is located between the servo and the filter and serves as a spacer, including the spring which can be seen on the picture. In the Ferrari 400 (contrary to other cars using the TH400) the filter is located at a distance from the servo.
3- This is the surprising information for me: that part (including the spring) is not critical. If it is not there, the gearbox works fine anyway. This has already been confirmed on my car with a long road test.

A complete refurbishing of my gearbox is planned for September this year, so I have plenty of time to confirm that the gearbox is OK without the part (which now sits on my desk).
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My last post was premature: the "unknown part" has nothing to do with the servo and the filter.

In fine, it is part of an assembly located at the end of the speedometer gear. The assembly is made up of three parts:

Pin (p/n 109241) the unknown part itself
Spring (p/n 109240)
Ball (p/n 109242)

I am not 100% clear on the exact role of this assembly, perhaps this is to absorb the vibrations when the speedometer gear rotates with the output shaft of the gearbox.

This assembly is on auto gearboxes for the 400 and the 400i first series, not on auto gearboxes for the 400 second series or 412 which seem to have a different speedometer gear.

Obviously not a critical assembly: my gearbox transmitted correct kilometers and speed for more than 10.000km over the last 6 years without this assembly in place.

When removing the speedometer gear from the box, nothing prevents the three parts from falling down and ending up in the oil pan (if not paying attention to this possibility).

All parts have been installed and the car road tested without problems.

The little movie below shows how the unknown part moves inside the speedometer gear. One can see the little ball at the beginning of the movie. The spring is inside the unknown part.

The picture shows the groove inside the speedometer gear where the little ball circulates.
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Thanks. I was expecting some form of recess at the far end of the cavity where the speedometer gear goes, in my mind the unknown part would have rested nicely against that recess and therefore this set-up would have helped in aligning the assembly. But that is not the case, hence I do not know if that explanation of mine is holding