The Stovebolt Site Forums The Shop Area Driveline Tranny I.D. and Suggestions Needed

Guys, I’m thinking someone in this forum can shed a light on this for me.
My ’59 project came with two engines that sat on the ground 20+ years.
One of them had a tranny attached that I assume to be the original.
Research has provided that this tranny is a Muncie 318 for my column shift.
Now I have a ’58 donor truck that I bought for spare parts for my ’59 project.
This truck appears to have had a column shift but the column shift lever, rod etc. is missing.
The truck has a floor shift and I walked it through, it’s a 4 speed.
I can’t show a picture of it but if you have a ’55-’59 Assembly Manual, it’s on Section 12, Sheet 40.00 and is the lower illustration (minus the E-brake hardware).
The drive shaft is weird to me, it has a rigid splined end that stabs into a yoke assembly mounted to the tranny. Can someone ID this thing? Second, is there a preference between the two?
Any input / suggestions appreciated. Thanks!
Jerry

I think I found what I was looking for as far as identifying the 4 speed.
HERE

It's a Muncie SM420

Now if I can get input on preference between the two?
Thanks!
Jerry

if you want to pull some stumps or climb some walls the 4 speed might be useful, but I'd take the 3 speed any day, a request in the parts wanted should turn up the shift bits easily

Bill

Thanks for the input Bill.
So you would prefer the 3 speed because ? (I have no experience here)
Is it that the 3 is better on the highway if not for heavy work?
Jerry

I'm a little out of my element as far as 3 spd vs. 4 spd, but, What are the ratios of these trannys?

I always liked the 4 speed with a granny gear. For a heavy load, this is a good way to take off. When light or empty, I use 2nd gear as my 1st gear, and leave granny gear out of the shift pattern. To me a 4 gear granny tranny is a 3 speed with an extra low gear for a heavy load start.

Short of lifting the rears and counting revolutions, I really couldn't tell you what the ratios are. I really would like to find out though. I think I'll do that soon... the more information I have to make a decision, the better.
It would be interesting to know if like you said, 2'nd, 3'rd and 4'th of the SM420 are like the 3 gears of the 318.
I kinda like the granny gear too. It reminds me of hay hauling days when all we had to do was keep the truck steering straight.
This must be what Bill was referring to concerning pulling stumps or climbing walls! It may also be a good gear for a parade.
What about the driveshaft? My Assembly manual illustrates the female spline should be on the driveshaft tube with a collar and seal. Maybe the one I have was modified backwards. I would think it would have the same effect... except it doesn't have a seal.
Jerry

Ratios for the SM420; 1rst-7.05:1, 2nd-3.58:1, 3rd-1.71:1, 4th-1:1. Reverse-6.78:1.
For comparison; SM318: 1rst-2.94:1, 2nd-1.68:1, 3rd-1:1, Reverse-2.94:1, Overdrive (if equipped) .70:1.
HD 3 speed (Borg-Warner) 1rst-3.17:1, 2nd-1.75:1, 3rd-1:1, Reverse-3.76:1

Awesome! Thank you Bill!
I'm favoring the 4 speed so far if the SM318 doesn't have overdrive.
How could I tell if it did? Is there a physical feature that would show this?
Jerry

The 3 speed overdrive has a couple of gizmos sticking out of the tail housing. One is a solenoid and it looks like an electric motor. The other is the governor.

There are pictures of it on the pages in this list.

Thanks Cletis!
So my 3 speed isn't equipped with overdrive... I'm still leaning toward the 4 speed so far.
It seems a lot of my project process has been decision making on which routes to go with all the options that get thrown in my path.
I'm certainly appreciative of all the help I get from this site.
Thank you all!
Jerry

Hopefully someday my wife and I can make that Texas Loop run... That'd be a real hoot!