18 speed transmission comes out of gear hard???

When the trans backs away from the flywheel housing that far the input shaft comes out of the pilot bearing causing the input shaft to loose support at the front of the shaft. This causes stress on the front bearing on the input shaft and front bearing retainer as it is now supporting the weight of the trans. The pocket bearing in the input shaft supports the front of the mainshaft. Without proper support of the mainshaft through the pocket bearing and the front bearing on the input shaft the mainshaft alignment could be compromised. I would look for the cause of the problem at the front of the trans and check for shift for wear. Does the clutch release properly?

 

I think that's a good plan of attack to better isolate the cause of the problem. When the trans is an inch away from the flywheel housing it's right at the point of the input shaft being out of the pilot bearing with no support to the front of the input shaft. This would allow the weight of the trans to hang from the clutch disc hubs and possibly bend the clutch discs.

 

Might have wrecked the pilot bearing and it still is not supporting the shaft.

 

Just install the clutch with the adjusting lock ring down onto the nice clean flywheel with a new pilot bearing in the flywheel.

 

The causes of clutch not releasing are;
Disc hub hanging up on input shaft splines.
Center plate hanging up on drive lugs in flywheel.
Bent discs.
Improper clutch adjustment.

Ideally, the buttons should all line up when installing a new clutch.