The Stovebolt Site Forums The Parking Lot Big Bolts 47 loadmaster transmission

Guys,
I have researched the forum and read the other talk on the SM420 vs. the "crash box". My 47 2 ton loadmaster has a crash box mated with a 53 235. I noticed on the other forum pages that the SM420 is apparently physically longer than the crash box. I would like to have a better shifting transmission in my truck but don't want to modify it too much. I have two questions:
1. What model and make is the crash box
2. Could the gears inside be replaced with helical gears for 2nd, 3rd and 4th?
This may sound crazy, but I wanted to explore the option before I just pull it and have to modify the clutch pedal and break pedal mounts.
Thanks.

Assuming you have a late 47 truck?
Can you swap to the SM420 and also swap the clutch and brake pedal assembly from a 48-53? and if needed shorten or lengthen the first section of driveshaft?

I don't think you can swap parts inside the two transmissions.

Grigg

Grigg,
It is a late year advanced design. I figured it might not work, but wanted to check. I can shift it by double clutching, but shifting down with a load when you come into a hill is no fun. I figured I would have to do some modification.
Thanks for the input.

Have you tried power shifting like big truck drivers do? I.E. Use clutch to start off. Then apply throttle, when maxed out in revs, let off the gas while pulling shifter out of gear. Wait for engine to slow to an appropriate rpm and re-engage next higher gear. when down shifting, do in reverse.

I'm confused - I thought the Advanced Designs were the introduction of the SM-420?

TexasT, is your trans. the original?

Also, what is the model name of the Crashbox 4s? Who made 'em?

Sorry, not trying to hi-jack the thread . . .

-Michael

I can power shift and it works on the way up, but downshifting is another story especially with a load.
This does appear to be the original tranny This truck other than the engine (casting numbers show it to be a 53) is pretty much original. It only hauled wheat 15 miles to the mill its entire life. The drive shaft does not seem to have been modified. I was surprised as well to find that it did not have a SM420 when I bought it. I contemplated adding a SM420 and an overdrive, but not sure if I want to or not.
Thanks for all the input.
Tim

I would like to convert my 46 1.5 ton to an automatic
I don't think a 350 turbohydro will bolt to a 216
What can I do?

"In 1948 Chevrolet was the first of the volume manufactures to offer a 4-speed synchro-mesh, helical gear transmission as regular equipment. It was an extra cost option. As a result of this complete redesign, the 4-speed transmission case was wider, higher, and longer. It was still of the same rigid, box-like cast iron construction as before. So that the new 4-speed transmission could be mounted interchangeably with the 3-speed transmission it was necessary to increase the length of the 3-speed transmission case and main shaft." (from a 1984 article about Advance-Design trucks in the Light Commercial vehicle Association magazine)

Tim you always have the most obscure references.

Keep 'em coming!