Posted by Keith in Washington on Tuesday, May 09, 2006 at 6:34PM :
In Reply to: spur gear transmission years made posted by dave on Monday, May 08, 2006 at 10:34PM :
The spur gear or crash box transmissions were used from 1946 to 1955. They went to the NP420 in 1956 (C4 and later models).
There were two versions of the earlier transmission. They are often called the "Up To" and "After" trans. The switch over between the two was at the end of the 1950 model year (WDX to B2 models). Models B3 to C3 had the "after" trans.
I have run both types (Up To and After). Not sure which is stronger. I have never run a NP420 as yet.
My B3's transmission was toast when I got it. The lower cluster shaft was badly worn. I assume it was an "after" trans. I am running a "Up To" trans now. It came from a 47 or 48 WDX and I just bolted it up after rinsing it out. I picked it up out of a junk yard for the PTO. In fact I took the whole winch assembly,bumpers with extensions, PTO and trans from the WDX and bolted into my truck.
Both trans ("Up To" and "After") have had a lot of rattle in 3rd gear. Apparently it is quite common. The "After" trans that was in the truck really rattled due to the worn lower cluster shaft and bearings. I will be putting in a NP 420 in the near future.
From what I understand the spur gear transmissions are actually stronger than the helically cut gear transmissions such as the NP420. I believe that you will break an axle much sooner that you would break any of these transmissions.
DC who is on this forum should be able to help you further on the strength questions.