The Stovebolt Site Forums The Parking Lot Big Bolts Parking Brake Conversion

Hello everyone,
I just picked up an SM420 with the parking brake on the output shaft. My truck is a 1948 2 ton and currently has parking brakes on the rear axles. Will I need to change the drive shaft before the hanger bearing to fit the brake? Is it a good upgrade? Is the single band brake better than the two rear axle cable brakes?

Parking brake on transmission is much better in my experience, it has the axle gear ratio in its favor.
Pretty sure it’s a bolt in swap, nothing tricky or else to replace.

Excellent! Thank you!

Which parking brake does your SM420 transmission have, the dual shoe (used on the big trucks) or the single external band type (used on the 1/2 to 1 ton trucks)?

Mike B

I’m curious to see a band type brake on an SM420, all I’ve seen are inner and outer shoe.

Here is the picture of it. Picked it up off Craig's List for $100. Did I pay too much? It has a PTO too.

That’s about the going rate for a used one in working condition. PTO only has value if you need it.

This is the transmission I have now.

Next time I'm in the shop I'll take a picture of one for you...it's sitting in the back on the floor!

Mike B

I attached the drive line brake to the transmission and ran into a few problems. First, the pto levers are in the way of the brake so I would have to swap for a cable PTO. Second, I appear to be missing the correct yoke from the brake. Anyone know whats up here?

With the brake the yoke is a “flange yoke” with a 4 bolt flange, not the spline yoke you show.
Which means you need a “companion flange” which has internal splines and the same 4 bolt pattern to match yoke, and drum may be bolted in between.

Did you not have a complete transmission with the brake on it, if so it should have all you need to swap.

It did not come with the flange yoke.

See if this helps...

Mike B

Here's a picture of the SM-420 Band Brake...

Mike B

That helps quite a lot actually. Thank you. I will try looking for a yoke like that. It wont work on our 6100 ton but It should fit the 4400.

Thanks for the picture Mike.
Was that a small truck only for a year or two type thing, do you know the application?

Mike B - Does Fitzy 440 need a piece of the contraption I have stored at JM's. As you may recall, I intend to do away with the brake on that SM420 and look for the pieces I need for a 1/2 ton (no brake) application.
If I had a picture of the piece (or description) in question I am headed out to the farm today and over the weekend.

HB,

I don't remember what you have, but I think he needs the yoke that would be still attached to your drive shaft (this is assuming you have a Dual Shoe set-up, not the Band type).

Mike B

Drum is 8x2-1/2"...

1955-66 3/4 & 1 ton (36,38 C20 & C30)
1958-62 1-1/2 ton (Ser. 4 & 40)
1965-66 1-1/2 ton (Ser. 50)

Mike B