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Old October 20th, 2020, 11:29 PM
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Ed Snyder Ed Snyder is offline
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Join Date: Jan 2013
Location: Medford, Oregon
Truck: 1962, 1965, 1967
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Default Re: What transmission is this?

Quote:
Originally Posted by IslandGMCguy View Post
I have my 1966 GMC 910 (Canadian) 1/2 ton pickup at a transmission shop for having the transmission rebuild. They told me it was a rare and unusual transmission in it?? It is a 4 speed manual on the floor. They said they were having a lot of problems finding internal parts for it. They told me the trans was a MNNP420 transmission. I have never heard of this and can’t find any info online either. Anyone know what this is???
If it's actually an SM420, and not an "MNNP420", then it is neither "rare" nor "unusual" as your shop claims. They were installed in thousands, if not millions, of trucks from 1947 to 1967.

Good luck with your rebuild!
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Ed Snyder
Medford, Oregon
1962 1000 Pickup 401M & Muncie 318 with overdrive
1962 K1000 Suburban 401M & SM420
1965 2500 Suburban 351C & SM420 with Watson overdrive
1967 CM1500 pickup 351E & NP435
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