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#1 |
Senior Member
![]() Join Date: Mar 2019
Location: Herculaneum MO (20 minutes south of St. Louis
Posts: 617
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SM420 help!
I have the SM420 out my 67 C20 to reseal it while doing my 292 swap. Well wouldn't you know my luck, when I opened it up I found a roll pin in the bottom of the case. The roll pin measures 1/8 by 1 inch.
Any help with where I should look. Where did this come from?
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67 C10 283 T5 swapped longbed fleetside = wife's daily driver 67 C20 292 (originally a 250)4speed longbed fleetside w/original wooden bed=my project truck 67 C10 283+.060 (so a 292 as well)T5 swapped longbed fleetside=my DD 72 C1500 Sierra Grande 350 TH350 longbed fleetside=wife's fair weather truck Can you tell we are fans of longbed fleetsides & 67s Chris |
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#2 |
Registered User
Join Date: Jan 2011
Location: Delaware and Long Island, New York
Posts: 3,455
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Re: SM420 help!
I would try to find an exploded view of the internals online.
I can check my 1967 chassis service manual. |
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#3 |
Senior Member
![]() Join Date: Dec 2009
Location: TN.
Posts: 8,097
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Re: SM420 help!
I found this online.
http://kinzers.com/don/landcruiser/t...x300/sm420.pdf I am subbed to see what you find out.
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________________________________________________________________________________________ ____________________________________________ 84 Chevy K-20 63 Impala (my high school car) http://67-72chevytrucks.com/vboard/s...Crew Cab Build |
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#4 |
Registered User
![]() Join Date: Feb 2000
Location: Maquoketa, Ia/ Orr, Mn
Posts: 3,008
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Re: SM420 help!
When I rebuilt my SM420 the only thing that resembled a roll pin was the small pin that held the reverse idler gear shaft in place, #57 in the exploded view in the pdf linked above. In order to remove the reverse idler gear shaft you have to drive that pin into the idler gear shaft (in the linked pdf above it is step 13 on the second page). It's possible an old one fell into the case during a rebuild in the past.
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'51 South Bend Model "9A" '56 Chevy 3600 NAPCO '74 Chevy Cheyenne Super K20-restored on 37's '72 GMC Sierra Custom K2500- in progress '08 GMC Envoy Denali '12 GMC Sierra 2500HD Denali '17 GMC Yukon XL VCCA member #58596 http://www.nohrco.com |
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#5 |
Senior Member
![]() Join Date: Mar 2003
Location: Colfax-California
Posts: 8,526
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Re: SM420 help!
Is it a solid pin or a split pin. #57 is in the back of the case and cannot come out unless the whole shaft goes backwards, even then I don't think it can make its way into the main body. I'm thinking a needle bearing or a pin out of the shift tower
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#6 |
Senior Member
![]() Join Date: Mar 2015
Location: washington
Posts: 2,240
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Re: SM420 help!
I would go by the function. Does it work correctly?
If it does I would just move on. I may be more pragmatic than some? |
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#7 |
Senior Member
![]() Join Date: Mar 2019
Location: Herculaneum MO (20 minutes south of St. Louis
Posts: 617
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Re: SM420 help!
Well I'm convinced it doesn't come from the transmission at all. Even though the diagram calls out 4 roll pins none of them are actually roll pins they are all solid pins. This is a roll pin as I stated.
Now there is a roll pin in the shifter assembly, however that pin can't be accessed with the shifter in the transmission. Also that pin is in place. How this got in the transmission I have no clue. I'm moving on.
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67 C10 283 T5 swapped longbed fleetside = wife's daily driver 67 C20 292 (originally a 250)4speed longbed fleetside w/original wooden bed=my project truck 67 C10 283+.060 (so a 292 as well)T5 swapped longbed fleetside=my DD 72 C1500 Sierra Grande 350 TH350 longbed fleetside=wife's fair weather truck Can you tell we are fans of longbed fleetsides & 67s Chris |
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#8 |
Registered User
Join Date: Apr 2014
Location: California
Posts: 946
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Re: SM420 help!
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#9 |
Registered User
Join Date: Mar 2014
Location: Tacoma Wa
Posts: 146
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Re: SM420 help!
It is common to use a roll pin to replace worn shifter guide lugs on the top of the trans. My guess someone dropped one down through the shifter opening. Other than that, there are roll pins that retain the 3-4 and 1-2 shifter yokes to the shifter shafts on the top loader.
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1953 3100 261cu in, sm420, 3.55 torque tube, omaha orange 1964 GMC 1000 series,custom, 305E, sm420 Last edited by sstock; 04-02-2022 at 07:00 PM. |
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#10 | |
Senior Member
![]() Join Date: Mar 2019
Location: Herculaneum MO (20 minutes south of St. Louis
Posts: 617
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Re: SM420 help!
Quote:
__________________
67 C10 283 T5 swapped longbed fleetside = wife's daily driver 67 C20 292 (originally a 250)4speed longbed fleetside w/original wooden bed=my project truck 67 C10 283+.060 (so a 292 as well)T5 swapped longbed fleetside=my DD 72 C1500 Sierra Grande 350 TH350 longbed fleetside=wife's fair weather truck Can you tell we are fans of longbed fleetsides & 67s Chris |
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#11 |
Registered User
Join Date: Mar 2014
Location: Tacoma Wa
Posts: 146
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Re: SM420 help!
Try again seems a little smug on your response. I have rebuilt over a dozen of these transmissions in the last year, On occasion, not very often I'll see a spring pin in where originally they were solid pins OEM. If someone was in there in the last 50 years it could of been replaced with a spring pin, fell out of the yoke and found the magnet on the bottom of the case. The second guy could of correctly replaced it with a solid pin and that would be an example of your situation. Believe me I seen some really shoddy workmanship in these transmission done by individuals that should of never removed the top loader in the first place.
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1953 3100 261cu in, sm420, 3.55 torque tube, omaha orange 1964 GMC 1000 series,custom, 305E, sm420 |
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#12 | |
Senior Member
![]() Join Date: Mar 2019
Location: Herculaneum MO (20 minutes south of St. Louis
Posts: 617
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Re: SM420 help!
Quote:
__________________
67 C10 283 T5 swapped longbed fleetside = wife's daily driver 67 C20 292 (originally a 250)4speed longbed fleetside w/original wooden bed=my project truck 67 C10 283+.060 (so a 292 as well)T5 swapped longbed fleetside=my DD 72 C1500 Sierra Grande 350 TH350 longbed fleetside=wife's fair weather truck Can you tell we are fans of longbed fleetsides & 67s Chris |
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#13 |
Senior Member
![]() Join Date: Dec 2009
Location: TN.
Posts: 8,097
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Re: SM420 help!
I looked in the 67 Service chassis Manuel I have.
I could not find any better info than I send in the last link I sent. Maybe 68panelman can find something in his Manuel.
__________________
________________________________________________________________________________________ ____________________________________________ 84 Chevy K-20 63 Impala (my high school car) http://67-72chevytrucks.com/vboard/s...Crew Cab Build |
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#14 |
Registered User
Join Date: Jan 2011
Location: Delaware and Long Island, New York
Posts: 3,455
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Re: SM420 help!
My manual is 10-60 series, probably same as yours. I also have a 70-80 but obviously no SM420's there. Same info as you. Actually didn't even show a 420?, Only 3 speed, 435, and Clark 5 speeds.
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#15 | |
Registered User
Join Date: Mar 2014
Location: Tacoma Wa
Posts: 146
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Re: SM420 help!
Quote:
__________________
1953 3100 261cu in, sm420, 3.55 torque tube, omaha orange 1964 GMC 1000 series,custom, 305E, sm420 |
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