The Stovebolt Site Forums The Shop Area Engine Shop Need HELP with Transmission choices

My truck is 1954 Chevy 3100 and currently has 283CI with original 4 speed trans and torque tube drive shaft & rear end.

I was told that the rear end I plan to upgrade my truck has 3.55 gears so I have been planning for an OD transmission upgrade. Turns out the rear end ratio is (15:41) 2.73 ratio. No OD required.

I want a top loader 3 (if there is such a thing) or 4 speed that would be compatible with my current bell housing and clutch. What years and models are my choices? I know it would begin with 1955 - ??.

With such a high rear end ratio, I wouldn't reccomend anything less than the sm420. The sm420 (used from about 1955-1967) is pretty much the same 4 speed that is currently in your truck, but it is set up for an open driveline. How well is the 283 built? If you have a relatively strong 283 you might be ablt to use a transmission with a higher 1st gear like a muncie or saginaw, but those transmissions would not be a topload design, and you would have to cut a new hole in the floor.

The Sm465 may also work, but the bearing retainer will have to be turned down by a machine shop to fit in your bellhousing.

Thanks for the reply, the sm420 sounds perfect. I want an bolt in, no machine work, no frigging... solution. I want the shifter to be where my stock one is.

The 283 is a 1967 from a C10/K10 with 2bl & PG. However I haven't been any deeper than the intake manifold; the starter, dist, heads, intake and carb are all numbers matching for a 1957 corvette 220 hp. I have replaced the intake with a Edlebrock Alum dual plane hi-rise, and Edlebrock 600cfm carb, added a Pertronix to the dist and the exhaust is dual with turbo mufflers and dumps just before the rear wheels (read low restriction).

It's not a race truck or a trailoring truck or hauling truck. Just me and perhaps a passenger, that's it.

Can I assume the sm420 was used on the half ton, 3/4 and 1 ton models?

Thanks again.

Yup! The shifter will be about 4 1/2 inches from the front of the transmission. In fact, the transmission you likely have is the sm420, but with the torque tube rear. You might be able to swap just the rear yoke of the transmission with that of an open drive sm420. It is probably easier to swap the whole transmission and then sell your closed driveline sm420.

I want the close ratios of the single grove input shaft all syncro three speed but would like a floor shift. I see that there is a T-15(?) floor shift tranny but with much wider ratios. will my three speed all syncro gearset fit it? is my tranny a t-16?
thanks
Roar