Swapping a 4 speed into my originally auto-equipped 383 '68 Coronet. The back of the crank was 'drilled' somewhat but apparently not enough. I measured the distance from the deepest point of the crank to the back of the bell to check for clearance and sure enough the input is too long.
I've never seen a forged crank that wasn't drilled "deep enough" to clear the input pilot...too small, yes, but too shallow?
Got a pic?
I will post one later this evening. Could be too small like you say. I measured the depth of the crank hole from the back face of the pilot bearing to the 'bottom' of the bore and get just about 1.5".
After ruminating on the above comments on how lazy I am,
I actually took the bell, clutch and flywheel off to make sure there wasn't anything misaligned or what have you - all good like I knew already.
As everyone knows, the pilot bearing lives in the TC register and acts more like a roller shaft support as opposed to the OE type bushing which is pressed deeper into the back of the crank. The difference being the input needs to be x amount longer to make full contact with the bushing. With the bearing, the only part of the input that touches anything is what jbc said - the .5" or so area in front of the splines. Anything beyond the point it makes contact with the bearing is dead weight and has no effect on anything.
In fact, the instructions that came with my parts (purchased from a well known and respected vendor) say that that particular area may need to be 'dressed down' so as not to cause interference with the bearing rollers. Apparently not all factory input shafts were machined to the the end of the snout when on the lathe - time is money. This was the case with mine. The difference in the O.D. of the two areas was about .010" inch. It made sense that could be the cause of the binding because I took the pilot bushing that came with the clutch and slid it on the input - there was no amount of force that was going to get it over that little ridge. The amount the trans was too long was almost the same as the length of the step. To prove the point further, if you look at images of reproduction input shafts from the various vendors, you's notice that little ledge is not there.
Once again ensuring that I wasn't being lazy or cutting corners, I sat there with a file and emery paper until well after midnight smoothing it out. Looks nice now but that was not the cause since the shaft still bottoms out before that area gets beyond the bearing. Such is life in a lazy person's world.
Moving ahead with the knowledge that I've done everything 'correctly'
, I jacked the unit up and inserted the input shaft into the pilot bearing as far as it would go but with no flywheel, clutch or bell to obscure my sight and scribed a line where it stopped. Between what I've cut/ground away already, I still need to cut at least 3/8" off the end to get it to seat fully in the bearing I.D. plus the recommended .125" clearance between the tip of the input and crank.
Pleas forgive me Moparts faithful for I have sinned and hereby offer my sincerest and most heart-felt apologies to the Mopar gods for my sheer laziness and egregious corner-cutting which has caused unspeakable damage to my holy and divine re manufactured 23 spline input shaft. I am so full of shame and sorrow for not shoving an entire tub of grease behind the pilot bearing to knock it out and then laboriously drilling my crank to accept the excess and unnecessary length of my input shaft so that I may some day this century enjoy my car.
