A833 input shaft diameter

[canadian duster]

So i spent the better part of 2 days trying to get this a833 mounted (behind a 360). I keep running into an issue where the input shaft will only get so far before binding. The crankshaft is a new forged eagle crank with a dorman pilot bushing in it. After further investigation, I've found that there is a raised edge on my input shaft about 1.5" from the end. An increase of .030" (for about 1") which stops it from entering the pilot bushing.
I cant find a spec for the input shaft diameter (its .747 at the end, bit .770 at the raised portion). I've noticed the pilot bushing in the crank is now a bit beat up. Something seems wrong with my setup as there is about 1" between the scattershield and transmission mounting tabs.

I'm at a loss because any pilot bushing or bearing is .750 I'd, and will not sit far enough into the clutch for the splines to mate.

My next move is to remove the engine again and try making everything outside the truck.

 

[AJ/FormS]

Have you tried pushing the bushing further in?
I have never seen a step on any of my A833 inputs, and mine is the same .750 all the way from front to back.
It is ~2.375 from the tip to the splines, the first 1/4 is beveled and the the last 1/4 is chamferred up to meet the splines. This leaves 1.75 of straight shaft. Add back the 1/4 " lead-in bevel and from tip to chamfer is a tic over 2". On mine, the bushing wear-line clearly ends at 1.75 from the tip, which being 1/2" from the splines.
Ergo you will need to take a trip to the lathe.

But there is something else wrong as indicated by the "about 1inch "statement. IMO your crank is not drilled deep enough, because your step is only 1/4 inch long. So even if you machine it off you could only gain that same 1/4 inch and only if that is the only problem. You need another 3/4 inch!
So I would see if that bushing will go further forward into the crank . In the factory crank there is a good sized step to stop the bushing.
Alternatively, you did install the clutch-disc with the flywheel-side, to the flywheel, right.

Many times the input shaft has to be cut off to fit automatic cranks and then we use the ball bearing pilot (sorry no PN) pressed into the TC register. This works real slick

 

[canadian duster]

Was actually thinking that as well. Concern was how far back was ok (I'm going to be reassuring the depth of hole in crank to be certain shaft isn't too long

 

[AJ/FormS]

The shaft is not too long lol, the hole may not be deep enough.
But at this point with the engine fully assembled, you may not have any choice but, to shorten the input. I guess you'll find out

 

[canadian duster]

Absolutely. Appreciate the response. I do have room to drive the pilot bushing in farther. The depth of the crank hole (deepest point to outside of pilot bushing) is 1.75". By driving in further, this should give me the clearance I need to get the splines in (as it was today, they were just touching the disk splines). In the end, I may need to take a bit off the end of the shaft.

 

[AJ/FormS]

Just don't drive it in too far, as the aftermarket crank may not have a stopper-step IDK.
And if it stops moving don't beat the crap out of it

 

[jtkaaa07]

Input shafts all have a step up in them like you described. I think the problem your running into is either bush depth, or wrong size ID of bushing . Take a micrometer and check ID versus diameter of input shaft. You should never get input shaft in far enough to have interface with that step up in the input shaft.

Jeff

 

[jtkaaa07]

This is a brand new input shaft on a customers 4 speed I’m building, you can see the step up.

 

[canadian duster]

Makes perfect sense then. I dont believe the bushing is far enough into the crankshaft. The front part of shaft is getting in, but I believe its getting hung up on the ridge, although the ridge on mine is a bit closer to the end than what those show.

 

[jtkaaa07]

Are you sure someone didn’t repair the input shaft, maybe it was spray welded or something, and they got the diameter wrong, just a thought, seen it done before.

 

[AJ/FormS]

Input shafts all have a step up in them like you described.

Before you say that absolutely; What year were your inputs manufactured?
None of my pre-1971 inputs are like that, and I don't recall ever seeing that step before; but the newest shaft I have ever seen would be maybe a 1974. I have never had to replace an input. The only one time I ever broke one, I stripped the teeth off it, which then went thru the rest of the gears, so I threw the whole thing away.
Oh wait, I have a couple of od boxes, those might be newer than 74.
No matter, the bushing usually rides at least a quarter inch further forward.

 

[jtkaaa07]

Every one I've ever seen has the step on it. All they did was start at a nominal size and it is machined to a finished size before they are hardened. On used ones it's not as noticeable as new, but they all have it.

 

[Daves69]

Maybe some of these dimensions for engagement depth that I found on a 440 steel automatic crank and un-cut input shaft can help. The green area would be where the pilot bushing resides..…..