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05-12-2019, 11:58 AM
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#1 |
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Registered User
Join Date: Jul 2008
Location: Eastern Oregon
Posts: 2,418
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M20 4 Speed Option ?
My 71 C20 has M20 listed on the SPID. Can you explain why ? Is it not the standard transmission ? Thanks fellas
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71 C-20 07 Magnum RT AWD |
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05-12-2019, 12:15 PM
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#2 |
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Registered User
Join Date: Apr 2018
Location: Riverdale, NJ
Posts: 85
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Re: M20 4 Speed Option ?
From what I understand, "m20" on your SPID means you have a "4 speed manual transmission". It doesn't mean you have a Muncie M20 transmission from the factory in your truck though, as that only came in cars. You either have a Muncie SM420, or its successor, the SM465. You most likely have an SM465 because the SM465 replaced the SM420 after 1968.
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05-12-2019, 01:04 PM
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#3 |
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Registered User
Join Date: Jul 2008
Location: Eastern Oregon
Posts: 2,418
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Re: M20 4 Speed Option ?
My bad ! The three speed on the tree was standard transmission right ? The M20 was optional so listed on SPID...thanks
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71 C-20 07 Magnum RT AWD |
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05-12-2019, 01:34 PM
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#4 |
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Senior Member
 
Join Date: Oct 2009
Location: Godley, TX
Posts: 17,995
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Re: M20 4 Speed Option ?
Yep, anything other than 3OTT would have appeared on the SPID.
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05-12-2019, 08:39 PM
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#5 |
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Registered User
Join Date: Feb 2018
Location: Doland SD
Posts: 836
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Re: M20 4 Speed Option ?
For the most part. My 71 gmc being the exemption. Has a factory 4 speed but not on the spid. Had a hole thread abut it bUT it never got solved
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 ( second times the charm) 71 gmc c15 307 sbc 373 rear gears positrac sm 465 trans. ( not listed on spid but is original )94 chevy k1500 350 tbi 373 rear gears 4l60e one wheel peel. Gutless 07 gmc sierra classic rcsb 4.3 lt 5 speed w/t 04 chevy Silverado 1500 ext cab 5.3 4l60e. 81 chevy Scottsdale k10 muncie sm465 Np208 10 bolt 8.2 ( Old Green) |
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05-12-2019, 09:25 PM
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#6 |
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Registered User
Join Date: Feb 2019
Location: Nor Cal
Posts: 822
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Re: M20 4 Speed Option ?
Any modifications to the SM465 so it doesn't have a granny gear?
More like a M20 or M21?
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1968 C20 Fleetside 396 4sp PS PB AC CST . https://www.youtube.com/watch?v=RWK8GgWD4uA |
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05-12-2019, 10:50 PM
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#7 |
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Senior Member
Join Date: Dec 2006
Location: Studio City, Calif.
Posts: 2,887
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Re: M20 4 Speed Option ?
oops, nm
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'69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme. Last edited by WorkinLonghorn; 05-12-2019 at 10:58 PM. |
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05-13-2019, 07:09 PM
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#8 | |
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Registered User
Join Date: Apr 2018
Location: Riverdale, NJ
Posts: 85
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Re: M20 4 Speed Option ?
Quote:
Yeah, just swap it out with an M20 
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