Help - Inherited a 1978 C20 with SM465 disassembled

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Gijordan07

Junior Member
Joined
Mar 20, 2021
Posts
5
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1
Location
Michigan
First Name
Jordan
Truck Year
1978
Truck Model
C20
Engine Size
5.7L
I inherited a 1978 C20 from my grandfather. He parked it about 25 years ago after an unknown transmission issue.

I've already got the engine running again (that was pretty cool to fire it up) but now need to get the transmission reassembled and put back in.

The issue is that he had the original SM465 2WD pulled out and disassembled. He also evidently had another transmission he must have purchased for parts, which is also disassembled. I'm not sure which internals went to which trans, and I do know that not all SM465s are the same depending on 2wd/4wd and slight changes over the 20+ years they used them.

Can anyone help me figure out which of these is the correct 4th gear? The one with the seal and plastic thing on it doesn't seem correct... but it's not chewed up on the tips of the teeth like the other one. Also not sure where it came from if it's not from one of the two disassembled transmissions, or where the other 4th gear went..

The speedo gears are also slightly different.. not sure which one is correct for 1978 c20 - what do I need to know - rear end ring gear?

Any help is appreciated.
 

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Dmack

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Joined
Mar 13, 2019
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Location
Central OR
First Name
Dave
Truck Year
1983
Truck Model
K20
Engine Size
350
No help on the internals, but since they are basically bulletproof and not rare, I would just look for a cheap used one. But good for you for using what you have.
 

pduffyd

Full Access Member
Joined
Sep 27, 2019
Posts
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Location
Melbourne, Australia
First Name
Paul
Truck Year
1975
Truck Model
C20
Engine Size
454
Hi gijordan07.
When I rebuilt mine a while back this guy took you through step by step.
Site down with a beer and watch part 1 and 2.

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