The Stovebolt Site Forums The Parking Lot '60-'66 Trucks 4 Speed Muncie Swap

I have a 62 C10 with a three speed tranny and I am curious if anyone has ever swapped a stock tranny out for a Muncie 4 speed. I've heard of it being done but was curious what some benefits would be and how people have gone about doing it themselves.

Thanks.

Matt,
Welcome to the forum. I'm sure many have done the swap to a 4 speed. Wait patiently and someone who has done it will chime in.
I'm curious. Are you unhappy with your current 3 speed? Has the 3 speed been acting up or maybe broken? The extra gear with a 4 speed will not be of any benefit for highway driving since 4th gear will be 1:1 ratio just like your current 3 speed.

What are your reasons for changing the transmission?

Thanks for the reply, I'm not really sure if I have any reason to switch, but there is a good chance that my current trans doesn't work (just a hunch, the truck has been sitting for 30+ years). That's really why I'm asking. I just want to know if there are any added benefits to a 4 speed.

Unless your 3 speed is full of water from sitting in a flood you probably have nothing to worry about. 🛠

Matt, I own a '64 C20 with the original 292 and Muncie SM420 4 speed. Lots of torque but you are going no where fast. I've been researching options to replace or enhance the muncie...they are few and often expensive. I would seriously rethink using your original 3 speed.

If you want to learn more about Muncie check out "http://www.novak-adapt.com/knowledge/transmissions/manual/sm420/". These guys use them in jeeps for rock crawling and have a lot of the parts to rebuild them.

I have the 1962 C10 with the SM420 (4 speed) and 3.90:1 gears in the back. It doesn't matter if you have 3 or 4 speeds, these trucks are limited to what the rear end gears will let them do. Both the 3 and 4 speeds from this era are top geared at 1:1. A more modern tranny might give you an over drive, but the way to increase top speed is the rear end gears.

If you are concerned with getting rid of the column shift, then the SM420 will do that, but then you need to change the tranny hump. There were 2 styles, high and low hump. Auto (powerglide) and 3 speed used the low hump and are the most common. The 4speed used the high hump, while not rare, they are less common. It's not a straight bolt on either. You will need to replace the removable tranny cover bolted to the floor of the cab, but you will also need to replace a piece that is spot welded to the firewall. Finding those is getting a bit tricky, but they are still out there.