Need Mystery Part Identified

[AZJeff]

I pulled my old 4.0 engine in preparation of installing my newly rebuilt short block, and when I decoupled the engine from the torque converter on the AW-4, I found a strange piece located where the pilot bearing would be found on a stick shift engine.

 

The piece is question has large flange that is inserted into the counterbore in the crankshaft in the same location where a pilot bearing would be found if the engine was connected to a manual transmission clutch.

 

The other end of these piece has a small pilot stub that engages a hole in the front of the torque converter.  This piece appears to be broken off flush in the front of the torque converter.  I have not attempted to remove it yet, so I don't know if it's a press fit into the converter or not.   The end that went to the crankshaft is loose enough that it fell out when the engine was lifted from the vehicle.

 

WHAT IS THIS PART?  I do not see it in the shop manuals I have for the XJ.   I have seen it in YouTube videos of removing an AW-4, but nobody mentions if it's a loose fit or a tight fit into the torque converter, or if it's part of the torque converter assembly, or a separate piece.

 

Wisdom and advice needed from those who have swapped engines or transmissions as separate items.   I guess an even more pertinent question would be:  is this part required?  What happens if I leave it out?  Will concentricity between the crankshaft and torque converter be reduced/lost?

[Htchevyii]

 

It looks like an alignment piece that broke off of your torque convertor. I'd check the flexplate for cracks or damage that might have led to this?

 

 

https://cobratransmission.com/aw4-torque-converter

 

[AZJeff]

32 minutes ago, Htchevyii said:

 

It looks like an alignment piece that broke off of your torque convertor. I'd check the flexplate for cracks or damage that might have led to this?

 

 

https://cobratransmission.com/aw4-torque-converter

 

Yup.  That’s the part.  I have already removed the flexplate from the old engine, and saw no cracks.   I am going to see if I can pull the broken part from the torque converter to study the failure mode here.

[pizzaman09]

That part has definitely seen fatigue damage.  I bet there is a broken stub of thread in your torque converter.

[AZJeff]

Yeah, as a retired mech engineer, I recognized that something is amiss to cause that failure.  So that pilot piece is threaded into that hole in the converter?

[Htchevyii]

I suppose that some shade tree could have forced it when it was misaligned or something?

[AZJeff]

47 minutes ago, Htchevyii said:

I suppose that some shade tree could have forced it when it was misaligned or something?

That’s a real possibility.   I am going to try to remove the broken stub from the converter, and get a machinist I know to make a repair to this piece, since I don’t think it’s available as an item unto itself.   And buying a new (reman) torque converter just to fix this piece is sort of extreme.