Trimming four speed input shaft.

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69CoronetRT

69CoronetRT

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I'd like to talk with someone that has experience in trimming the end a four speed input shaft.

Does anyone have experience in doing this or can you recommend someone?
 
I've done it a couple of times. What do you want to know?
 
Why?
Crank not drilled or rough drilled for pilot bushing?
 
I just had to trim mine last weekend. Was kind of a PITA as I was under the vehicle with the trans when I discovered the input was about 1/2 to long for the crank on the small block I was using. I pretty much took the angle grinder ground the input back the amount of the factory tapper then re tappered it worked like a charm.
 
I had to cut the input shaft when I converted my Coronet to a 4 speed. Automatic cars did not have the crank drilled to the proper depth. It can be really difficult to drill it deep enough so you wind up cutting the input shaft.

Nothing to know about really, just cut it and re-chamfer the edges. May take trial and error so start conservative.
 
69CoronetRT said:
I'd like to talk with someone that has experience in trimming the end a four speed input shaft.

Does anyone have experience in doing this or can you recommend someone?
Click to expand...

CRANK PILOT-MIN DIMENSIONS.jpg


PILOT BUSHING DRAWING.jpg
 
No need.

Support your engine front down (out of the car) on a stable surface.

Use the flywheel & mount a magnetic drill press on it. (many places rent them if you do not have one)

Drill hole in crankshaft deeper in a large enough diameter to clear the input shaft.

DO NOT open it up for a bronze bushing, leave meat for any future machining. (magnetic drill press not precise enough)

Use the Dakota style input bearing & all set.
 
I do not recommend drilling the crankshaft if it is cast. I have first hand knowledge of two people local to me who drilled into the crankshaft's oil galley. Also Roy (RIP) had the same experience.
 
Well, you do need to be smart enough to know when to stop. ;-)
 
Why screw up a very hard to find part when it can be done right?
 
I don't think trimming an input shaft is screwing anything up. It's not like it won't fully function as intended.
 
Alaskan_TA said:
No need.

Support your engine front down (out of the car) on a stable surface.

Use the flywheel & mount a magnetic drill press on it. (many places rent them if you do not have one)

Drill hole in crankshaft deeper in a large enough diameter to clear the input shaft.

DO NOT open it up for a bronze bushing, leave meat for any future machining. (magnetic drill press not precise enough)

Use the Dakota style input bearing & all set.
Click to expand...

I don't have access to such a mag press, but when I was contemplating putting a 5 speed in the 5.9 gas pickup I used to have WHICH IS NOT DRILLED AT ALL beyond the converter---I was considering just making a "jig" onto the bell to hold a drill bit in a threaded device and chuck and then drill the thing LOL BY RUNNING THE ENGINE
 
I trimmed mine 1/2-3/4 inch with just a cutoff wheel because that's what I had. I then shaped the end like stock. Installed a roller bearing. So far, so good for 5000 miles.
 
I hate seeing this! Another original 833 gone to toast!

Once this is done there is no return unless one has lots of standard input shafts!

I got burned by this in 1982, My 383 had the crank bore and the bushing, when someone made this mod on a trans I purchased. My Super Bee was never correct and had clutch issues until I figured out what happened.

The Folks at Eaton Transmissions in Atlanta fixed me up When I went to buy replacement parts and bearings. Without the crank support it kept burning the front

bearing and leaking badly!
 
1969383S said:
I hate seeing this! Another original 833 gone to toast!

Once this is done there is no return unless one has lots of standard input shafts!

I got burned by this in 1982, My 383 had the crank bore and the bushing, when someone made this mod on a trans I purchased. My Super Bee was never correct and had clutch issues until I figured out what happened.

The Folks at Eaton Transmissions in Atlanta fixed me up When I went to buy replacement parts and bearings. Without the crank support it kept burning the front

bearing and leaking badly!
Click to expand...
Nobody's saying anything about not having crankshaft support. Where did you see that even implied? It's a very accepted mod and done correctly has no ill consequences.
 
RustyRatRod said:
Nobody's saying anything about not having crankshaft support. Where did you see that even implied? It's a very accepted mod and done correctly has no ill consequences.
Click to expand...

I did not,

Merely stating another wasted stock input shaft!
 
1969383S said:
I did not,

Merely stating another wasted stock input shaft!
Click to expand...
No, it's another USED modified input shaft. If you read what's been posted, you will understand the input shaft does have crankshaft support from a pilot bearing that presses into the crankshaft register. Just because you may not like it, doesn't mean it does not work. It does and very well.
 
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