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4 speed install, cutting input shaft #2684995
08/06/19 02:38 PM
08/06/19 02:38 PM
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Spahn Ranch
RMCHRGR Offline OP
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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 knew I had to cut the input down but I wasn't comfortable making one large cut to start since based on my measurements, it looks like I could be lopping off 3/4" or more.

I went against the math and tried a smaller conservative cut to see if it would go but I'm still seeing about a 3/8" gap before the trans meets the bell. Since I can't really see the input with the trans in place to see if something is way out of whack, the 3/8" gap would indicate that it's still bottoming out.

Does 3/4" + seem like an excessive amount to have to trim or is this 'normal' for this scenario where you're trying to seat it in a crank that was originally mated to an auto? The input looks like it would be pretty short after it's all said and done.

Or - could I be doing something wrong with how I'm installing the trans? I have the clutch, flywheel and bell installed and I aligned everything with an old cut-off input shaft. I went with a pilot bearing instead of the bushing and it's installed correctly. Should the bell be installed on the trans first? Should the bell bolts be left loose until the unit is all the way in? There is a point where the input goes in then it just stops.No fiddling with the trans jack angle or bell height helped. I even tried smacking the case with a piece of wood and a hammer but it's a no go. I figured if I'm having to resort to this type of tomfoolery, somethin' ain't right. This should not be that hard!

Thanks fort any input.


'71 Duster
'17 Ram 1500
Re: 4 speed install, cutting input shaft [Re: RMCHRGR] #2685013
08/06/19 03:41 PM
08/06/19 03:41 PM
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I would shoot for .125(1/8 inch) clearance and or max end play between the input shaft and the crankshaft when sitting still with every thing tighten up as it will be run including the drive shaft up twocents You don't want the input shaft ever touching the back of the crankshaft hole, never tsk


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: 4 speed install, cutting input shaft [Re: Cab_Burge] #2685023
08/06/19 04:06 PM
08/06/19 04:06 PM
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Lincoln Nebraska
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RapidRobert Offline
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I read a procedure where they just drilled straight into the back of the crankshaft to make it deep enough for the input shaft to fit, it said it was "meatball surgery" so it did not have to be precise (sounds like Rick Ehrenbergs lingo!) so it mighta been a Mopar Action article & iirc it said you also what you are thinking that you could cut the input shaft then use a roller bearing # 53009180AB in the recess where the automatic trans nub goes to support everything (I did that once on an A230 3 speed swap).


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Re: 4 speed install, cutting input shaft [Re: Cab_Burge] #2685024
08/06/19 04:13 PM
08/06/19 04:13 PM
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Minnesota
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I've run into this a couple times over the years. Have seen an inch or more cut off the end of the input shaft, as it does not appear the depth of the crank drilling was consistent. Chamfer the edge of the input shaft so it goes through the pilot bearing easier. The advice about it not touching the end of the crank is wise.

I assume you used one of the later model pilot bearings that fits into the flange at the end of the crank!

Last edited by peabodyracing; 08/06/19 04:15 PM.

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Re: 4 speed install, cutting input shaft [Re: RapidRobert] #2685048
08/06/19 05:22 PM
08/06/19 05:22 PM
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yes the PN 53009180AB I have a pic of it but I cant get it to load from the camera onto the computer. I just got another one & it was listed at $31.10 & with a slight discount they let me have it for $27.77 out the door.


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Re: 4 speed install, cutting input shaft [Re: peabodyracing] #2685049
08/06/19 05:23 PM
08/06/19 05:23 PM
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Originally Posted by peabodyracing
I've run into this a couple times over the years. Have seen an inch or more cut off the end of the input shaft, as it does not appear the depth of the crank drilling was consistent. Chamfer the edge of the input shaft so it goes through the pilot bearing easier. The advice about it not touching the end of the crank is wise.

I assume you used one of the later model pilot bearings that fits into the flange at the end of the crank!


Thanks, that's what I was hoping to hear about how much I might need to cut, just seems a little crazy to have to trim that much. Glad I took baby steps. Maybe the second time will yield a straighter cut.. sawzall

Yes, I did use the pilot bearing.


'71 Duster
'17 Ram 1500
Re: 4 speed install, cutting input shaft [Re: RMCHRGR] #2685054
08/06/19 05:34 PM
08/06/19 05:34 PM
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Mopar was trying to conserve money spent on machining all low deck crankshafts for pilot bushing back then, I've seen a bunch of 361 and 383 automatic motors with the real shallow pilot hole for use in the crankshaft grinding lathes to finish grinding the cores shruggy
Not so on the 440 automatic cranks, they where deeper but not the same I.D as the stick shift cranks where confused shruggy

Last edited by Cab_Burge; 08/06/19 05:35 PM.

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Re: 4 speed install, cutting input shaft [Re: RapidRobert] #2685057
08/06/19 05:37 PM
08/06/19 05:37 PM
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That bearing is available at Rock Auto. I bought several a while back I think I paid less than $8.00. It is dumb to cut the input shaft of the trans just bore a hole in the crank it affects nothing.


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Re: 4 speed install, cutting input shaft [Re: 1DGEMAN] #2685127
08/06/19 08:51 PM
08/06/19 08:51 PM
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Originally Posted by 1DGEMAN
That bearing is available at Rock Auto. I bought several a while back I think I paid less than $8.00. It is dumb to cut the input shaft of the trans just bore a hole in the crank it affects nothing.


Can you explain why you think it's dumb to trim the input shaft? To make this work, it's either drill the crank or trim the input shaft- what's the difference? Neither option is perfect but that's the nature of the beast when you're trying to make parts work in an application they were never intended for. shruggy

At this point, I'd rather not go through the exercise of removing the bellhousing, clutch, flywheel and pilot bearing and then stand there with a hand drill for however long reaming a blind hole in the back of my crank. Much easier to trim the input with the trans on a stand.


'71 Duster
'17 Ram 1500
Re: 4 speed install, cutting input shaft [Re: RMCHRGR] #2685137
08/06/19 09:21 PM
08/06/19 09:21 PM
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The obvious issue with cutting the end off the input shaft is that the input shaft will be too short to work in the correctly drilled crankshaft, but even then, you can still use the bearing.
I believe I cut about an inch off the input shaft on the a833 I cut, but it was a long time ago. That trans saw a lot of B motors after we cut the end off the input shaft. It was much easier to find big blocks when we didn't need the deep drilled crank. Gene

Re: 4 speed install, cutting input shaft [Re: RMCHRGR] #2685211
08/07/19 05:35 AM
08/07/19 05:35 AM
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Originally Posted by RMCHRGR
Originally Posted by 1DGEMAN
That bearing is available at Rock Auto. I bought several a while back I think I paid less than $8.00. It is dumb to cut the input shaft of the trans just bore a hole in the crank it affects nothing.


Can you explain why you think it's dumb to trim the input shaft? To make this work, it's either drill the crank or trim the input shaft- what's the difference? Neither option is perfect but that's the nature of the beast when you're trying to make parts work in an application they were never intended for. shruggy

At this point, I'd rather not go through the exercise of removing the bellhousing, clutch, flywheel and pilot bearing and then stand there with a hand drill for however long reaming a blind hole in the back of my crank. Much easier to trim the input with the trans on a stand.


It just means you are too lazy to do it correctly. I have drilled several cranks not that big of a deal. What other short cuts did you take on your car?


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Re: 4 speed install, cutting input shaft [Re: poorboy] #2685212
08/07/19 05:38 AM
08/07/19 05:38 AM
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Originally Posted by poorboy
The obvious issue with cutting the end off the input shaft is that the input shaft will be too short to work in the correctly drilled crankshaft, but even then, you can still use the bearing.
I believe I cut about an inch off the input shaft on the a833 I cut, but it was a long time ago. That trans saw a lot of B motors after we cut the end off the input shaft. It was much easier to find big blocks when we didn't need the deep drilled crank. Gene


You make it seem like it is a big deal to drill a hole. It is not.


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Re: 4 speed install, cutting input shaft [Re: RMCHRGR] #2685280
08/07/19 10:30 AM
08/07/19 10:30 AM
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Cut off what you need to on the end of the input shaft and stuff it in there or drill out the crank. Either way, but cutting it doesn't affect the area where the bushing or the bearing ride on the input shaft. That part of the input shaft is closer to the splines.


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1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)
Re: 4 speed install, cutting input shaft [Re: 1DGEMAN] #2685316
08/07/19 12:09 PM
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It just means you are too lazy to do it correctly.
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Re: 4 speed install, cutting input shaft [Re: RMCHRGR] #2685338
08/07/19 01:13 PM
08/07/19 01:13 PM
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Originally Posted by RMCHRGR
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?


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Re: 4 speed install, cutting input shaft [Re: John_Kunkel] #2685344
08/07/19 01:22 PM
08/07/19 01:22 PM
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McGregor,Iowa 52157
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I put a 451 together a whilst back with a Muscle Motors kit and they used a 440 crank and it just had a divot from what looked to be from the drill bit, just spot faced

Re: 4 speed install, cutting input shaft [Re: John_Kunkel] #2685370
08/07/19 02:58 PM
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Originally Posted by John_Kunkel
Originally Posted by RMCHRGR
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, eyes 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' eyes, 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.


'71 Duster
'17 Ram 1500
Re: 4 speed install, cutting input shaft [Re: RMCHRGR] #2685372
08/07/19 03:04 PM
08/07/19 03:04 PM
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Grand Prairie,Texas
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That should quite down the naysayer. Some people just know everything there is about doing a job but actually know very little. Good going RMC.

Re: 4 speed install, cutting input shaft [Re: stumpy] #2685379
08/07/19 03:54 PM
08/07/19 03:54 PM
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Rio Linda, CA
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There's a difference between being a naysayer (it can't be so) and being a skeptic (show me).

The OP states he has a '68 crank which would be forged. The typical forged crank flange is shown in the diagram below. Both the initial drilling and the final bore are sufficient in diameter and depth to clear the .750" pilot on a 833.

Yes, some later cranks have only a "divot" instead of a drilled hole but I've never seen (not the same as saying it can't be) a '68 like that, that's why I asked for a pic...for my own edification.

pilot_bushing_hole.jpg

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Re: 4 speed install, cutting input shaft [Re: RMCHRGR] #2685395
08/07/19 04:21 PM
08/07/19 04:21 PM
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We drilled a cast crank still inside the engine a while back. Borrowed a magnetic base drill press. Worked perfectly. We did have piece of steel cut and bolted to the engine to provide a surface to mount the drill.

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