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SM465 vs. SM420
If it's a toss-up between running an SM420 or an SM465 in your truck, you may want to consider going for the easier-to-find-and-get-parts-for SM465 if it will physically fit.
| SM465
| SM420
| Length(in.)
| 12.0
| 10.4
| Height (in.)
| 18.0
| 17.0
| Weight (lbs.)
| 175
| 135
| Input Shaft
| 1 1/8-in., 10-spline or
1 1/2-in., 10-spline
| 1 1/8-in., 10-spline
| Output Shaft
| 10-spline (early 4WD),
35-spline (2WD)
32-spline (late 4WD)
| 10-spline
| BearingRetainer Diameter (in.)
| 5.125
| 4.686
| GearRatios
|
|
| 1st
| 6.55:1
| 7.06:1
| 2nd
| 3.58:1
| 3.58:1
| 3rd
| 1.7:1
| 1.71:1
| 4th
| 1.1:1
| 1.1:1
| Reverse
| 6.09:1
| 6.78:1
|  From left to right, these...  From left to right, these are the components on this 32-spline output-style main shaft: First gear, Reverse gear with First-Second gear synchro assembly underneath, Second gear, Third gear, Third-Fourth synchro assembly.  From left to right, these...  From left to right, these are the components on the countershaft: First, Reverse, Second, Third, Anaheim Gear cluster spacer, and Fourth gear. Shaft Options
Anaheim Gear knows how to mix and match factory components to build a transmission that's right for your application. Because we were mating our SM465 to a Klune-V "David" underdrive with a 32-spline input, Massey suggested swapping mainshafts to the later 32-spline version (bottom). Anaheim Gear even had a fac-tory SM465-to-NP208 adapter that would work for our application. The result is a much stronger setup than if we had used a spud shaft to connect the 4WD 10-spline output (top) to our crawler box. The only drawback is that the 32-spline shaft will be a few inches longer than the coarse output and spud shaft combo. However, we've got enough driveshaft to accommodate it. Here's the main reason SM465s... Here's the main reason SM465s jump out of gear. The Fourth gear and Third gear are held in place on the countershaft with snap rings. Under load, Third gear wants to walk forward and Fourth gear wants to walk back. After time the snap rings flex enough to allow the tranny to jump out of gear. Third Gear Jumpout Fix
If there's one thing the SM465 is infamous for it's its tendency to jump out of Third gear. Here's what Anaheim Gear does to prevent this problem.
 Anaheim Gear simply replaces...  Anaheim Gear simply replaces the snap rings with its cluster spacer (PN 14020811). The collar is slid on and then the Fourth gear is pressed onto the mainshaft. Now there's nowhere for the gears to go.  Another reason is that the...  Another reason is that the factory Third-Fourth synchro assembly has teeth that are square-cut. Anaheim Gear replaces these synchro assemblies with aftermarket assemblies that have diamond-cut teeth. The different shape forces the synchro into the gear and keeps it from jumping out.  Finally, Anaheim Gear replaces...  Finally, Anaheim Gear replaces the springs in the shift rails with heavier springs to prevent any chance of jumpout. Problem: Worn output shaft... Problem: Worn output shaft and collar
Description: The 4WD versions had a short output that uses a collar to connect to the transfer case input. Over time, these collars wear and can damage the splines of the transmission output shaft.
Solution: Replace mainshaft with usable core. Problems, Solutions, and Things to Look Out For
Rebuilding an SM465 isn't rocket science, but there are a few things that can go awry. The first of which is starting with a core that's hashed. Before you delve into any rebuild, make sure your transmission is in good shape. Anaheim Gear media-blasts and tumbles each part so it can be checked before assembly, then runs the transmissions on a dyno to make sure everything is perfect before it sends a rebuilt unit out the door. If you're tackling an at-home rebuild and discover part of your core is shot, chances are Anaheim Gear can supply you with a new or used replacement part to get you back into the game.
 Problem: Damaged throwout...  Problem: Damaged throwout bearing surface on input bearing retainer.
Description: In heavy towing or other high-heat, extreme-duty applications, the throwout bearing can spin on the retainer and gall the surface.
Solution: Light abrasions can be smoothed with emery cloth. More severe gouges (shown) will require the input bearing retainer to be replaced.  Problem: Reverse idler shaft...  Problem: Reverse idler shaft not installed as shown.
Description: When installing the reverse idler gear, the shaft must be installed with the cut horizontal and the recessed portion facing the bottom of the transmission.
Solution: Install it right, dummy.  Problem: Worn mainshaft bushings....  Problem: Worn mainshaft bushings.
Description: The SM465 used removable bushings on the mainshaft instead of roller or sacrificial bearings. You should check their condition before reinstalling your gears on the mainshaft.
Solution: Replace bushings if necessary.
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