A833 Input Shaft Woes

[CL3406]

That combo will give you a starter gear of 9.21; a little tall for a 340, but you're a couple of hundred pounds lighter than my S-clone, so , depending on the rest of your combo,it should be OK. At 3100 your tires would have to have a roll-out of 76.24, or about 24.26 tall. That's a pretty small tire; Like maybe a 215/60-14 . You probably wouldn't want to run something that small on a 340car.
More likely you'd run a 245/60-15 @26.7" tall, and rolling out at 83.9 inches. This would get you 2817@ 60 and Zero-slip, ie with a manual trans.
But really, with a 340 you should be running the tallest widest tire that will fit, on a wheel well-centered in the tub, whatever it takes.
And I'll tell you why; cuz if you don't,and if you run a DP carb; there's a VERY good chance, that she'll be sideways at the oddest times, and pointing backwards some of those times.Don't ask me how I know, I'm 65 years old and learned to drive in a 70 Swinger
That taller tire will throw your speed-O out about 10%.... and it will make starting out require a bit more rpm than before.
I run a 27 inch tire,with an HO 360, and wouldn't want anything less than a 10/1 starter gear. We'll see how your 9.21 works out. If you got a 292/108 cam Then you're gonna want a whole nuther comb,lol

I have experienced "the sideways at odd times" LOL. 340 4spd Dart with smaller tires did exactly what you say. I am 54 so had a few Mopars over the years. My tire size will be 215/70/14, cam pretty much stock grind. This set up is very close to a previous Dart I owned, except for the 73 close ratio trans. If things aren't perfect, just another weekend to change the 8 3/4 out. All good! Thanks for your info.

 

[AJ/FormS]

I have experienced "the sideways at odd times" LOL. 340 4spd Dart with smaller tires did exactly what you say. I am 54 so had a few Mopars over the years. My tire size will be 215/70/14, cam pretty much stock grind. This set up is very close to a previous Dart I owned, except for the 73 close ratio trans. If things aren't perfect, just another weekend to change the 8 3/4 out. All good! Thanks for your info.

Those tires math out to 25.85 tall and roll-out at 81.2, so 60= 2910@ zero-slip.
2.0hrs to RnR the chunk is plenty of time.

With a stockish cam,in a streeter, a better solution might be the standard 2.66 low box. It will get you more TM but without the hiway rpm penalty of a bigger chunk,but notice the 1-2 shift differences;

B) the T/A 2.47 box and 3.91s... 9.66-6.92-5.24-3.91 .....60mph=3050rpm
A) the T/A 2.47 box and 3.73s.... 9.21-6.60-5.00-3.73 .....60=2910 the current combo
C) the std 2.66 box and 3.73s... 9.92-7.16-5.18-3.73 .....60=2910
E) early-A,3.09 box and 3.73.... 11.53-7.16-5.22-3.73 .... 60=2910
D) the std 2.66 box and 3.55s.... 9.44-6.82-4.97-3.55 .....60=2770
F) early-A,3.09 box and 3.55s... 10.97-6.82-4.97-3.55..... 60=2770
G) early-A,3.09 box and 3.23s..... 9.98-6.20-4.52-3.23 .....60=2520

Altho I could easily run the G combo with my 367,I choose to run the F
for a streeter;
the best first gear, let's you dump it and go; usually between 9 and 11 to 1
the best second gear is the one that gets you to 60mph and revved right out to your combos power-peak plus about 200/300 rpm.
third gear is hardly important, as long as it's about half way between second and fourth.
the best top gear is the one that lets you idle down the road, just above the rpm where reversion has stopped in your intake, or where your idle vacuum peaks.

 

[CL3406]

Those tires math out to 25.85 tall and roll-out at 81.2, so 60= 2910@ zero-slip.
2.0hrs to RnR the chunk is plenty of time.

With a stockish cam,in a streeter, a better solution might be the standard 2.66 low box. It will get you more TM but without the hiway rpm penalty of a bigger chunk,but notice the 1-2 shift differences;

B) the T/A 2.47 box and 3.91s... 9.66-6.92-5.24-3.91 .....60mph=3050rpm
A) the T/A 2.47 box and 3.73s.... 9.21-6.60-5.00-3.73 .....60=2910 the current combo
C) the std 2.66 box and 3.73s... 9.92-7.16-5.18-3.73 .....60=2910
E) early-A,3.09 box and 3.73.... 11.53-7.16-5.22-3.73 .... 60=2910
D) the std 2.66 box and 3.55s.... 9.44-6.82-4.97-3.55 .....60=2770
F) early-A,3.09 box and 3.55s... 10.97-6.82-4.97-3.55..... 60=2770
G) early-A,3.09 box and 3.23s..... 9.98-6.20-4.52-3.23 .....60=2520

Altho I could easily run the G combo with my 367,I choose to run the F
for a streeter;
the best first gear, let's you dump it and go; usually between 9 and 11 to 1
the best second gear is the one that gets you to 60mph and revved right out to your combos power-peak plus about 200/300 rpm.
third gear is hardly important, as long as it's about half way between second and fourth.
the best top gear is the one that lets you idle down the road, just above the rpm where reversion has stopped in your intake, or where your idle vacuum peaks.

You must like math? LOL. I have copied all this data for a couple friends currently building 4 spd Mopars. Good stuff!

 

[JAndrea]

Thanks for all of the great information that followed up this post.

I did find one person through FABO that had a 23 spline, 25 tooth shaft, but I went with a local (Mn) contact I made who had two of them, and is located just a few miles from my house.

Thanks to Chuck Lofgren, part owner of KTRE Engines in East Bethel, MN.

I kept track of my contacts, so anybody running into this post in the future can simply reach out to me and I can source you to a couple of more 23 spline, 25 tooth input shafts that I'm currently aware of.